chore: prepare Tokio v1.38.0 (#6601)

The previous NamedPipeServer doc example seemed to imply that the return
type of `NamedPipeServer::connect()` was a
`Future<Result<some_kind_of_client>>>`, however, `connect()` returns a
`Future<Result<()>>>`. The following line of code reopening the pipe
would shadow the newly connected pipe immediately, making the following
spawned task pointless. Hopefully these changes make it more clear what
should be happening in the example.

.cargo/audit.toml

@@ -1,8 +0,0 @@
-# See https://github.com/rustsec/rustsec/blob/59e1d2ad0b9cbc6892c26de233d4925074b4b97b/cargo-audit/audit.toml.example for example.
-
-[advisories]
-ignore = [
-    # We depend on nix 0.22 only via mio-aio, a dev-dependency.
-    # https://github.com/tokio-rs/tokio/pull/4255#issuecomment-974786349
-    "RUSTSEC-2021-0119",
-]

.cargo/config

@@ -1,2 +0,0 @@
-# [build]
-# rustflags = ["--cfg", "tokio_unstable"]

.circleci/config.yml

@@ -2,7 +2,7 @@ version: 2.1
 jobs:
   test-arm:
     machine:
-      image: ubuntu-2004:202101-01
+      image: default
     resource_class: arm.medium
     environment:
       # Change to pin rust version

.cirrus.yml

@@ -1,8 +1,10 @@
+only_if: $CIRRUS_TAG == '' && ($CIRRUS_PR != '' || $CIRRUS_BRANCH == 'master' || $CIRRUS_BRANCH =~ 'tokio-.*')
+auto_cancellation: $CIRRUS_BRANCH != 'master' && $CIRRUS_BRANCH !=~ 'tokio-.*'
 freebsd_instance:
-  image: freebsd-12-4-release-amd64
+  image_family: freebsd-14-0
 env:
   RUST_STABLE: stable
-  RUST_NIGHTLY: nightly-2022-10-25
+  RUST_NIGHTLY: nightly-2024-05-05
   RUSTFLAGS: -D warnings
 
 # Test FreeBSD in a full VM on cirrus-ci.com.  Test the i686 target too, in the
@@ -11,9 +13,8 @@ env:
 # the system's binaries, so the environment shouldn't matter.
 task:
   name: FreeBSD 64-bit
-  auto_cancellation: $CIRRUS_BRANCH != 'master' && $CIRRUS_BRANCH !=~ 'tokio-.*'
   setup_script:
-    - pkg install -y bash curl
+    - pkg install -y bash
     - curl https://sh.rustup.rs -sSf --output rustup.sh
     - sh rustup.sh -y --profile minimal --default-toolchain $RUST_STABLE
     - . $HOME/.cargo/env
@@ -26,12 +27,11 @@ task:
 
 task:
   name: FreeBSD docs
-  auto_cancellation: $CIRRUS_BRANCH != 'master' && $CIRRUS_BRANCH !=~ 'tokio-.*'
   env:
     RUSTFLAGS: --cfg docsrs --cfg tokio_unstable
     RUSTDOCFLAGS: --cfg docsrs --cfg tokio_unstable -Dwarnings
   setup_script:
-    - pkg install -y bash curl
+    - pkg install -y bash
     - curl https://sh.rustup.rs -sSf --output rustup.sh
     - sh rustup.sh -y --profile minimal --default-toolchain $RUST_NIGHTLY
     - . $HOME/.cargo/env
@@ -44,9 +44,8 @@ task:
 
 task:
   name: FreeBSD 32-bit
-  auto_cancellation: $CIRRUS_BRANCH != 'master' && $CIRRUS_BRANCH !=~ 'tokio-.*'
   setup_script:
-    - pkg install -y bash curl
+    - pkg install -y bash
     - curl https://sh.rustup.rs -sSf --output rustup.sh
     - sh rustup.sh -y --profile minimal --default-toolchain $RUST_STABLE
     - . $HOME/.cargo/env

.clippy.toml

@@ -1 +0,0 @@
-msrv = "1.49"

.github/labeler.yml

@@ -1,8 +1,28 @@
 
-R-loom:
+R-loom-sync:
 - tokio/src/sync/*
 - tokio/src/sync/**/*
-- tokio-util/src/sync/*
-- tokio-util/src/sync/**/*
-- tokio/src/runtime/*
-- tokio/src/runtime/**/*
+
+R-loom-time-driver:
+- tokio/src/runtime/time/*
+- tokio/src/runtime/time/**/*
+
+R-loom-current-thread:
+- tokio/src/runtime/scheduler/*
+- tokio/src/runtime/scheduler/current_thread/*
+- tokio/src/runtime/task/*
+- tokio/src/runtime/task/**
+
+R-loom-multi-thread:
+- tokio/src/runtime/scheduler/*
+- tokio/src/runtime/scheduler/multi_thread/*
+- tokio/src/runtime/scheduler/multi_thread/**
+- tokio/src/runtime/task/*
+- tokio/src/runtime/task/**
+
+R-loom-multi-thread-alt:
+- tokio/src/runtime/scheduler/*
+- tokio/src/runtime/scheduler/multi_thread_alt/*
+- tokio/src/runtime/scheduler/multi_thread_alt/**
+- tokio/src/runtime/task/*
+- tokio/src/runtime/task/**

.github/workflows/audit.yml

@@ -21,7 +21,7 @@ jobs:
     runs-on: ubuntu-latest
     if: "!contains(github.event.head_commit.message, 'ci skip')"
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
 
       - name: Audit Check
         # https://github.com/rustsec/audit-check/issues/2

.github/workflows/labeler.yml

@@ -4,6 +4,10 @@ on:
 
 # See .github/labeler.yml file
 
+concurrency:
+  group: ${{ github.workflow }}-${{ github.event.pull_request.number || github.sha }}
+  cancel-in-progress: true
+
 permissions:
   contents: read
 

.github/workflows/loom.yml

@@ -7,8 +7,14 @@ on:
 
 name: Loom
 
+concurrency:
+  group: ${{ github.workflow }}-${{ github.event.pull_request.number || github.sha }}
+  cancel-in-progress: true
+
 env:
-  RUSTFLAGS: -Dwarnings
+  RUSTFLAGS: -Dwarnings --cfg loom --cfg tokio_unstable -C debug_assertions
+  LOOM_MAX_PREEMPTIONS: 2
+  LOOM_MAX_BRANCHES: 10000
   RUST_BACKTRACE: 1
   # Change to specific Rust release to pin
   rust_stable: stable
@@ -17,32 +23,100 @@ permissions:
   contents: read
 
 jobs:
-  loom:
-    name: loom
+  loom-sync:
+    name: loom tokio::sync
     # base_ref is null when it's not a pull request
-    if: github.repository_owner == 'tokio-rs' && (contains(github.event.pull_request.labels.*.name, 'R-loom') || (github.base_ref == null))
+    if: github.repository_owner == 'tokio-rs' && (contains(github.event.pull_request.labels.*.name, 'R-loom-sync') || (github.base_ref == null))
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - name: Install Rust ${{ env.rust_stable }}
+        uses: dtolnay/rust-toolchain@master
+        with:
+            toolchain: ${{ env.rust_stable }}
+      - uses: Swatinem/rust-cache@v2
+      - name: run tests
+        run: cargo test --lib --release --features full -- --nocapture sync::tests
+        working-directory: tokio
+
+  loom-time-driver:
+    name: loom time driver
+    # base_ref is null when it's not a pull request
+    if: github.repository_owner == 'tokio-rs' && (contains(github.event.pull_request.labels.*.name, 'R-loom-time-driver') || (github.base_ref == null))
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - name: Install Rust ${{ env.rust_stable }}
+        uses: dtolnay/rust-toolchain@master
+        with:
+            toolchain: ${{ env.rust_stable }}
+      - uses: Swatinem/rust-cache@v2
+      - name: run tests
+        run: cargo test --lib --release --features full -- --nocapture runtime::time::tests
+        working-directory: tokio
+
+  loom-current-thread:
+    name: loom current-thread scheduler
+    # base_ref is null when it's not a pull request
+    if: github.repository_owner == 'tokio-rs' && (contains(github.event.pull_request.labels.*.name, 'R-loom-current-thread') || (github.base_ref == null))
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - name: Install Rust ${{ env.rust_stable }}
+        uses: dtolnay/rust-toolchain@master
+        with:
+            toolchain: ${{ env.rust_stable }}
+      - uses: Swatinem/rust-cache@v2
+      - name: run tests
+        run: cargo test --lib --release --features full -- --nocapture loom_current_thread
+        working-directory: tokio
+
+  loom-multi-thread:
+    name: loom multi-thread scheduler
+    # base_ref is null when it's not a pull request
+    if: github.repository_owner == 'tokio-rs' && (contains(github.event.pull_request.labels.*.name, 'R-loom-multi-thread') || (github.base_ref == null))
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        scope:
-          - --skip loom_pool
-          - loom_pool::group_a
-          - loom_pool::group_b
-          - loom_pool::group_c
-          - loom_pool::group_d
-          - time::driver
+        include:
+          - scope: loom_multi_thread::group_a
+          - scope: loom_multi_thread::group_b
+          - scope: loom_multi_thread::group_c
+          - scope: loom_multi_thread::group_d
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - name: Install Rust ${{ env.rust_stable }}
         uses: dtolnay/rust-toolchain@master
         with:
             toolchain: ${{ env.rust_stable }}
       - uses: Swatinem/rust-cache@v2
       - name: loom ${{ matrix.scope }}
-        run: cargo test --lib --release --features full -- --nocapture $SCOPE
+        run: cargo test --lib --release --features full -- $SCOPE
+        working-directory: tokio
+        env:
+          SCOPE: ${{ matrix.scope }}
+
+  loom-multi-thread-alt:
+    name: loom ALT multi-thread scheduler
+    # base_ref is null when it's not a pull request
+    if: github.repository_owner == 'tokio-rs' && (contains(github.event.pull_request.labels.*.name, 'R-loom-multi-thread-alt') || (github.base_ref == null))
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        include:
+          - scope: loom_multi_thread_alt::group_a
+          - scope: loom_multi_thread_alt::group_b
+          - scope: loom_multi_thread_alt::group_c
+          - scope: loom_multi_thread_alt::group_d
+    steps:
+      - uses: actions/checkout@v4
+      - name: Install Rust ${{ env.rust_stable }}
+        uses: dtolnay/rust-toolchain@master
+        with:
+            toolchain: ${{ env.rust_stable }}
+      - uses: Swatinem/rust-cache@v2
+      - name: loom ${{ matrix.scope }}
+        run: cargo test --lib --release --features full -- $SCOPE
         working-directory: tokio
         env:
-          RUSTFLAGS: --cfg loom --cfg tokio_unstable -Dwarnings
-          LOOM_MAX_PREEMPTIONS: 2
-          LOOM_MAX_BRANCHES: 10000
           SCOPE: ${{ matrix.scope }}

.github/workflows/pr-audit.yml

@@ -8,6 +8,10 @@ on:
     paths:
       - '**/Cargo.toml'
 
+concurrency:
+  group: ${{ github.workflow }}-${{ github.event.pull_request.number || github.sha }}
+  cancel-in-progress: true
+
 permissions:
   contents: read
 
@@ -16,7 +20,7 @@ jobs:
     runs-on: ubuntu-latest
     if: "!contains(github.event.head_commit.message, 'ci skip')"
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
 
       - name: Install cargo-audit
         run: cargo install cargo-audit

.github/workflows/stress-test.yml

@@ -5,6 +5,10 @@ on:
     branches:
       - master
 
+concurrency:
+  group: ${{ github.workflow }}-${{ github.event.pull_request.number || github.sha }}
+  cancel-in-progress: true
+
 env:
   RUSTFLAGS: -Dwarnings
   RUST_BACKTRACE: 1
@@ -23,19 +27,19 @@ jobs:
         stress-test:
           - simple_echo_tcp
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - name: Install Rust ${{ env.rust_stable }}
         uses: dtolnay/rust-toolchain@master
         with:
             toolchain: ${{ env.rust_stable }}
-      - uses: Swatinem/rust-cache@v2
       - name: Install Valgrind
         uses: taiki-e/install-action@valgrind
 
+      - uses: Swatinem/rust-cache@v2
       # Compiles each of the stress test examples.
       - name: Compile stress test examples
         run: cargo build -p stress-test --release --example ${{ matrix.stress-test }}
 
       # Runs each of the examples using Valgrind. Detects leaks and displays them.
       - name: Run valgrind
-        run: valgrind --error-exitcode=1 --leak-check=full --show-leak-kinds=all ./target/release/examples/${{ matrix.stress-test }}
+        run: valgrind --error-exitcode=1 --leak-check=full --show-leak-kinds=all --fair-sched=yes ./target/release/examples/${{ matrix.stress-test }}

.gitignore

@@ -2,3 +2,4 @@ target
 Cargo.lock
 
 .cargo/config.toml
+.cargo/config

CONTRIBUTING.md

@@ -131,8 +131,11 @@ cargo check --all-features
 cargo test --all-features
 ```
 
-Clippy must be run using the MSRV, so Tokio can avoid having to `#[allow]` new
-lints whose fixes would be incompatible with the current MSRV:
+Ideally, you should use the same version of clippy as the one used in CI
+(defined by `env.rust_clippy` in [ci.yml][ci.yml]), because newer versions
+might have new lints:
+
+[ci.yml]: .github/workflows/ci.yml
 
 <!--
 When updating this, also update:
@@ -146,23 +149,31 @@ When updating this, also update:
 -->
 
 ```
-cargo +1.49.0 clippy --all --tests --all-features
+cargo +1.77 clippy --all --tests --all-features
 ```
 
-When building documentation normally, the markers that list the features
-required for various parts of Tokio are missing. To build the documentation
-correctly, use this command:
+When building documentation, a simple `cargo doc` is not sufficient. To produce
+documentation equivalent to what will be produced in docs.rs's builds of Tokio's
+docs, please use:
 
 ```
-RUSTDOCFLAGS="--cfg docsrs" RUSTFLAGS="--cfg docsrs" cargo +nightly doc --all-features
+RUSTDOCFLAGS="--cfg docsrs --cfg tokio_unstable" RUSTFLAGS="--cfg docsrs --cfg tokio_unstable" cargo +nightly doc --all-features [--open]
 ```
 
-To build documentation including Tokio's unstable features, it is necessary to
-pass `--cfg tokio_unstable` to both RustDoc *and* rustc. To build the
-documentation for unstable features, use this command:
+This turns on indicators to display the Cargo features required for
+conditionally compiled APIs in Tokio, and it enables documentation of unstable
+Tokio features. Notice that it is necessary to pass cfg flags to both RustDoc
+*and* rustc.
+
+There is a more concise way to build docs.rs-equivalent docs by using [`cargo
+docs-rs`], which reads the above documentation flags out of Tokio's Cargo.toml
+as docs.rs itself does.
+
+[`cargo docs-rs`]: https://github.com/dtolnay/cargo-docs-rs
 
 ```
-RUSTDOCFLAGS="--cfg docsrs --cfg tokio_unstable" RUSTFLAGS="--cfg docsrs --cfg tokio_unstable" cargo +nightly doc --all-features
+cargo install --locked cargo-docs-rs
+cargo +nightly docs-rs [--open]
 ```
 
 The `cargo fmt` command does not work on the Tokio codebase. You can use the
@@ -170,10 +181,10 @@ command below instead:
 
 ```
 # Mac or Linux
-rustfmt --check --edition 2018 $(git ls-files '*.rs')
+rustfmt --check --edition 2021 $(git ls-files '*.rs')
 
 # Powershell
-Get-ChildItem . -Filter "*.rs" -Recurse | foreach { rustfmt --check --edition 2018 $_.FullName }
+Get-ChildItem . -Filter "*.rs" -Recurse | foreach { rustfmt --check --edition 2021 $_.FullName }
 ```
 The `--check` argument prints the things that need to be fixed. If you remove
 it, `rustfmt` will update your files locally instead.
@@ -181,24 +192,58 @@ it, `rustfmt` will update your files locally instead.
 You can run loom tests with
 ```
 cd tokio # tokio crate in workspace
-LOOM_MAX_PREEMPTIONS=1 RUSTFLAGS="--cfg loom" \
+LOOM_MAX_PREEMPTIONS=1 LOOM_MAX_BRANCHES=10000 RUSTFLAGS="--cfg loom -C debug_assertions" \
     cargo test --lib --release --features full -- --test-threads=1 --nocapture
 ```
+Additionally, you can also add `--cfg tokio_unstable` to the `RUSTFLAGS` environment variable to
+run loom tests that test unstable features. 
 
 You can run miri tests with
 ```
-MIRIFLAGS="-Zmiri-disable-isolation -Zmiri-tag-raw-pointers" PROPTEST_CASES=10 \
+MIRIFLAGS="-Zmiri-disable-isolation -Zmiri-tag-raw-pointers" \
     cargo +nightly miri test --features full --lib
 ```
 
+### Performing spellcheck on tokio codebase
+
+You can perform spell-check on tokio codebase. For details of how to use the spellcheck tool, feel free to visit
+https://github.com/drahnr/cargo-spellcheck
+```
+# First install the spell-check plugin
+cargo install --locked cargo-spellcheck
+
+# Then run the cargo spell check command
+cargo spellcheck check
+```
+
+if the command rejects a word, you should backtick the rejected word if it's code related. If not, the 
+rejected word should be put into `spellcheck.dic` file. 
+
+Note that when you add a word into the file, you should also update the first line which tells the spellcheck tool
+the total number of words included in the file
+
 ### Tests
 
 If the change being proposed alters code (as opposed to only documentation for
 example), it is either adding new functionality to Tokio or it is fixing
 existing, broken functionality. In both of these cases, the pull request should
 include one or more tests to ensure that Tokio does not regress in the future.
-There are two ways to write tests: integration tests and documentation tests
-(Tokio avoids unit tests as much as possible).
+There are two ways to write tests: [integration tests][integration-tests]
+and [documentation tests][documentation-tests].
+(Tokio avoids [unit tests][unit-tests] as much as possible).
+
+Tokio uses [conditional compilation attributes][conditional-compilation]
+throughout the codebase, to modify rustc's behavior. Code marked with such
+attributes can be enabled using RUSTFLAGS and RUSTDOCFLAGS environment
+variables. One of the most prevalent flags passed in these variables is
+the `--cfg` option. To run tests in a particular file, check first what
+options #![cfg] declaration defines for that file.
+
+For instance, to run a test marked with the 'tokio_unstable' cfg option,
+you must pass this flag to the compiler when running the test.
+```
+$ RUSTFLAGS="--cfg tokio_unstable" cargo test -p tokio --all-features --test rt_metrics
+```
 
 #### Integration tests
 
@@ -209,6 +254,31 @@ utilities available to use in tests, no matter the crate being tested.
 The best strategy for writing a new integration test is to look at existing
 integration tests in the crate and follow the style.
 
+#### Fuzz tests
+
+Some of our crates include a set of fuzz tests, this will be marked by a
+directory `fuzz`. It is a good idea to run fuzz tests after each change.
+To get started with fuzz testing you'll need to install
+[cargo-fuzz](https://github.com/rust-fuzz/cargo-fuzz).
+
+`cargo install --locked cargo-fuzz`
+
+To list the available fuzzing harnesses you can run;
+
+```bash
+$ cd tokio
+$ cargo fuzz list
+fuzz_linked_list
+````
+
+Running a fuzz test is as simple as;
+
+`cargo fuzz run fuzz_linked_list`
+
+**NOTE**: Keep in mind that by default when running a fuzz test the fuzz
+harness will run forever and will only exit if you `ctrl-c` or it finds
+a bug.
+
 #### Documentation tests
 
 Ideally, every API has at least one [documentation test] that demonstrates how to
@@ -285,6 +355,29 @@ example would explicitly use `Timeout::new`. For example:
 /// # }
 ```
 
+### Benchmarks
+
+You can run benchmarks locally for the changes you've made to the tokio codebase.
+Tokio currently uses [Criterion](https://github.com/bheisler/criterion.rs) as its benchmarking tool. To run a benchmark
+against the changes you have made, for example, you can run;
+
+```bash
+cd benches
+
+# Run all benchmarks.
+cargo bench
+
+# Run all tests in the `benches/fs.rs` file
+cargo bench --bench fs
+
+# Run the `async_read_buf` benchmark in `benches/fs.rs` specifically.
+cargo bench async_read_buf
+
+# After running benches, you can check the statistics under `tokio/target/criterion/`
+```
+
+You can also refer to Criterion docs for additional options and details.
+
 ### Commits
 
 It is a recommended best practice to keep your changes as logically grouped as
@@ -308,14 +401,16 @@ A good commit message should describe what changed and why.
     and no more than 72 characters)
   * be entirely in lowercase with the exception of proper nouns, acronyms, and
     the words that refer to code, like function/variable names
-  * be prefixed with the name of the sub crate being changed (without the `tokio-`
-    prefix) and start with an imperative verb. If modifying `tokio` proper,
-    omit the crate prefix.
+  * start with an imperative verb
+  * not have a period at the end
+  * be prefixed with the name of the module being changed; usually this is the
+    same as the M-* label on the PR
 
   Examples:
 
-  * timer: introduce `Timeout` and deprecate `Deadline`
-  * export `Encoder`, `Decoder`, `Framed*` from tokio_codec
+  * time: introduce `Timeout` and deprecate `Deadline`
+  * codec: export `Encoder`, `Decoder`, `Framed*`
+  * ci: fix the FreeBSD ci configuration
 
 2. Keep the second line blank.
 3. Wrap all other lines at 72 columns (except for long URLs).
@@ -332,7 +427,7 @@ A good commit message should describe what changed and why.
 Sample complete commit message:
 
 ```txt
-subcrate: explain the commit in one line
+module: explain the commit in one line
 
 Body of commit message is a few lines of text, explaining things
 in more detail, possibly giving some background about the issue
@@ -633,3 +728,7 @@ When releasing a new version of a crate, follow these steps:
    entry for that release version into your editor and close the window.
 
 [keep-a-changelog]: https://github.com/olivierlacan/keep-a-changelog/blob/master/CHANGELOG.md
+[unit-tests]: https://doc.rust-lang.org/rust-by-example/testing/unit_testing.html
+[integration-tests]: https://doc.rust-lang.org/rust-by-example/testing/integration_testing.html
+[documentation-tests]: https://doc.rust-lang.org/rust-by-example/testing/doc_testing.html
+[conditional-compilation]: https://doc.rust-lang.org/reference/conditional-compilation.html

Cargo.toml

@@ -1,5 +1,5 @@
 [workspace]
-
+resolver = "2"
 members = [
   "tokio",
   "tokio-macros",
@@ -14,3 +14,6 @@ members = [
   "tests-build",
   "tests-integration",
 ]
+
+[workspace.metadata.spellcheck]
+config = "spellcheck.toml"

LICENSE

@@ -1,25 +1,21 @@
-Copyright (c) 2022 Tokio Contributors
+MIT License
 
-Permission is hereby granted, free of charge, to any
-person obtaining a copy of this software and associated
-documentation files (the "Software"), to deal in the
-Software without restriction, including without
-limitation the rights to use, copy, modify, merge,
-publish, distribute, sublicense, and/or sell copies of
-the Software, and to permit persons to whom the Software
-is furnished to do so, subject to the following
-conditions:
+Copyright (c) Tokio Contributors
 
-The above copyright notice and this permission notice
-shall be included in all copies or substantial portions
-of the Software.
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
 
-THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF
-ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED
-TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
-PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT
-SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
-CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
-OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR
-IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
-DEALINGS IN THE SOFTWARE.
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

README.md

@@ -56,7 +56,7 @@ Make sure you activated the full features of the tokio crate on Cargo.toml:
 
 ```toml
 [dependencies]
-tokio = { version = "1.24.1", features = ["full"] }
+tokio = { version = "1.38.0", features = ["full"] }
 ```
 Then, on your main.rs:
 
@@ -132,6 +132,8 @@ project.
 In addition to the crates in this repository, the Tokio project also maintains
 several other libraries, including:
 
+* [`axum`]: A web application framework that focuses on ergonomics and modularity.
+
 * [`hyper`]: A fast and correct HTTP/1.1 and HTTP/2 implementation for Rust.
 
 * [`tonic`]: A gRPC over HTTP/2 implementation focused on high performance, interoperability, and flexibility.
@@ -142,21 +144,18 @@ several other libraries, including:
 
 * [`tracing`] (formerly `tokio-trace`): A framework for application-level tracing and async-aware diagnostics.
 
-* [`rdbc`]: A Rust database connectivity library for MySQL, Postgres and SQLite.
-
-* [`mio`]: A low-level, cross-platform abstraction over OS I/O APIs that powers
-  `tokio`.
+* [`mio`]: A low-level, cross-platform abstraction over OS I/O APIs that powers `tokio`.
 
 * [`bytes`]: Utilities for working with bytes, including efficient byte buffers.
 
-* [`loom`]: A testing tool for concurrent Rust code
+* [`loom`]: A testing tool for concurrent Rust code.
 
+[`axum`]: https://github.com/tokio-rs/axum
 [`warp`]: https://github.com/seanmonstar/warp
 [`hyper`]: https://github.com/hyperium/hyper
 [`tonic`]: https://github.com/hyperium/tonic
 [`tower`]: https://github.com/tower-rs/tower
 [`loom`]: https://github.com/tokio-rs/loom
-[`rdbc`]: https://github.com/tokio-rs/rdbc
 [`tracing`]: https://github.com/tokio-rs/tracing
 [`mio`]: https://github.com/tokio-rs/mio
 [`bytes`]: https://github.com/tokio-rs/bytes
@@ -187,7 +186,21 @@ When updating this, also update:
 
 Tokio will keep a rolling MSRV (minimum supported rust version) policy of **at
 least** 6 months. When increasing the MSRV, the new Rust version must have been
-released at least six months ago. The current MSRV is 1.49.0.
+released at least six months ago. The current MSRV is 1.63.
+
+Note that the MSRV is not increased automatically, and only as part of a minor
+release. The MSRV history for past minor releases can be found below:
+
+ * 1.30 to now - Rust 1.63
+ * 1.27 to 1.29 - Rust 1.56
+ * 1.17 to 1.26 - Rust 1.49
+ * 1.15 to 1.16 - Rust 1.46
+ * 1.0 to 1.14 - Rust 1.45
+
+Note that although we try to avoid the situation where a dependency transitively
+increases the MSRV of Tokio, we do not guarantee that this does not happen.
+However, every minor release will have some set of versions of dependencies that
+works with the MSRV of that minor release.
 
 ## Release schedule
 
@@ -202,20 +215,28 @@ warrants a patch release with a fix for the bug, it will be backported and
 released as a new patch release for each LTS minor version. Our current LTS
 releases are:
 
- * `1.18.x` - LTS release until June 2023
- * `1.20.x` - LTS release until September 2023.
+ * `1.32.x` - LTS release until September 2024. (MSRV 1.63)
+ * `1.36.x` - LTS release until March 2025. (MSRV 1.63)
 
 Each LTS release will continue to receive backported fixes for at least a year.
 If you wish to use a fixed minor release in your project, we recommend that you
 use an LTS release.
 
 To use a fixed minor version, you can specify the version with a tilde. For
-example, to specify that you wish to use the newest `1.18.x` patch release, you
+example, to specify that you wish to use the newest `1.32.x` patch release, you
 can use the following dependency specification:
 ```text
-tokio = { version = "~1.18", features = [...] }
+tokio = { version = "~1.32", features = [...] }
 ```
 
+### Previous LTS releases
+
+ * `1.8.x` - LTS release until February 2022.
+ * `1.14.x` - LTS release until June 2022.
+ * `1.18.x` - LTS release until June 2023.
+ * `1.20.x` - LTS release until September 2023.
+ * `1.25.x` - LTS release until March 2024.
+
 ## License
 
 This project is licensed under the [MIT license].

benches/Cargo.toml

@@ -2,13 +2,17 @@
 name = "benches"
 version = "0.0.0"
 publish = false
-edition = "2018"
+edition = "2021"
+
+[features]
+test-util = ["tokio/test-util"]
 
 [dependencies]
 tokio = { version = "1.5.0", path = "../tokio", features = ["full"] }
-bencher = "0.1.5"
+criterion = "0.5.1"
 rand = "0.8"
 rand_chacha = "0.3"
+num_cpus = "1.16.0"
 
 [dev-dependencies]
 tokio-util = { version = "0.7.0", path = "../tokio-util", features = ["full"] }
@@ -22,16 +26,40 @@ name = "spawn"
 path = "spawn.rs"
 harness = false
 
+[[bench]]
+name = "sync_broadcast"
+path = "sync_broadcast.rs"
+harness = false
+
 [[bench]]
 name = "sync_mpsc"
 path = "sync_mpsc.rs"
 harness = false
 
+[[bench]]
+name = "sync_mpsc_oneshot"
+path = "sync_mpsc_oneshot.rs"
+harness = false
+
+[[bench]]
+name = "sync_watch"
+path = "sync_watch.rs"
+harness = false
+
+[[bench]]
+name = "rt_current_thread"
+path = "rt_current_thread.rs"
+harness = false
+
 [[bench]]
 name = "rt_multi_threaded"
 path = "rt_multi_threaded.rs"
 harness = false
 
+[[bench]]
+name = "sync_notify"
+path = "sync_notify.rs"
+harness = false
 
 [[bench]]
 name = "sync_rwlock"
@@ -57,3 +85,13 @@ harness = false
 name = "copy"
 path = "copy.rs"
 harness = false
+
+[[bench]]
+name = "time_now"
+path = "time_now.rs"
+harness = false
+
+[[bench]]
+name = "time_timeout"
+path = "time_timeout.rs"
+harness = false

benches/copy.rs

@@ -1,4 +1,4 @@
-use bencher::{benchmark_group, benchmark_main, Bencher};
+use criterion::{criterion_group, criterion_main, Criterion};
 
 use rand::{Rng, SeedableRng};
 use rand_chacha::ChaCha20Rng;
@@ -29,7 +29,7 @@ const WRITE_SERVICE_PERIOD: Duration = Duration::from_millis(20);
 // because another writer claimed the buffer space
 const PROBABILITY_FLUSH_WAIT: f64 = 0.1;
 
-/// A slow writer that aims to simulate HDD behaviour under heavy load.
+/// A slow writer that aims to simulate HDD behavior under heavy load.
 ///
 /// There is a limited buffer, which is fully drained on the next write after
 /// a time limit is reached. Flush waits for the time limit to be reached
@@ -64,7 +64,7 @@ impl SlowHddWriter {
     ) -> std::task::Poll<Result<(), std::io::Error>> {
         // If we hit a service interval, the buffer can be cleared
         let res = self.service_intervals.poll_tick(cx).map(|_| Ok(()));
-        if let Poll::Ready(_) = res {
+        if res.is_ready() {
             self.buffer_used = 0;
         }
         res
@@ -123,7 +123,7 @@ impl AsyncWrite for SlowHddWriter {
         cx: &mut std::task::Context<'_>,
         bufs: &[std::io::IoSlice<'_>],
     ) -> std::task::Poll<Result<usize, std::io::Error>> {
-        let writeable = bufs.into_iter().fold(0, |acc, buf| acc + buf.len());
+        let writeable = bufs.iter().fold(0, |acc, buf| acc + buf.len());
         self.write_bytes(cx, writeable)
     }
 
@@ -174,65 +174,77 @@ fn rt() -> tokio::runtime::Runtime {
         .unwrap()
 }
 
-fn copy_mem_to_mem(b: &mut Bencher) {
+fn copy_mem_to_mem(c: &mut Criterion) {
     let rt = rt();
 
-    b.iter(|| {
-        let task = || async {
-            let mut source = repeat(0).take(SOURCE_SIZE);
-            let mut dest = Vec::new();
-            copy(&mut source, &mut dest).await.unwrap();
-        };
+    c.bench_function("copy_mem_to_mem", |b| {
+        b.iter(|| {
+            let task = || async {
+                let mut source = repeat(0).take(SOURCE_SIZE);
+                let mut dest = Vec::new();
+                copy(&mut source, &mut dest).await.unwrap();
+            };
 
-        rt.block_on(task());
-    })
+            rt.block_on(task());
+        })
+    });
 }
 
-fn copy_mem_to_slow_hdd(b: &mut Bencher) {
+fn copy_mem_to_slow_hdd(c: &mut Criterion) {
     let rt = rt();
 
-    b.iter(|| {
-        let task = || async {
-            let mut source = repeat(0).take(SOURCE_SIZE);
-            let mut dest = SlowHddWriter::new(WRITE_SERVICE_PERIOD, WRITE_BUFFER);
-            copy(&mut source, &mut dest).await.unwrap();
-        };
+    c.bench_function("copy_mem_to_slow_hdd", |b| {
+        b.iter(|| {
+            let task = || async {
+                let mut source = repeat(0).take(SOURCE_SIZE);
+                let mut dest = SlowHddWriter::new(WRITE_SERVICE_PERIOD, WRITE_BUFFER);
+                copy(&mut source, &mut dest).await.unwrap();
+            };
 
-        rt.block_on(task());
-    })
+            rt.block_on(task());
+        })
+    });
 }
 
-fn copy_chunk_to_mem(b: &mut Bencher) {
+fn copy_chunk_to_mem(c: &mut Criterion) {
     let rt = rt();
-    b.iter(|| {
-        let task = || async {
-            let mut source = ChunkReader::new(CHUNK_SIZE, READ_SERVICE_PERIOD).take(SOURCE_SIZE);
-            let mut dest = Vec::new();
-            copy(&mut source, &mut dest).await.unwrap();
-        };
 
-        rt.block_on(task());
-    })
+    c.bench_function("copy_chunk_to_mem", |b| {
+        b.iter(|| {
+            let task = || async {
+                let mut source =
+                    ChunkReader::new(CHUNK_SIZE, READ_SERVICE_PERIOD).take(SOURCE_SIZE);
+                let mut dest = Vec::new();
+                copy(&mut source, &mut dest).await.unwrap();
+            };
+
+            rt.block_on(task());
+        })
+    });
 }
 
-fn copy_chunk_to_slow_hdd(b: &mut Bencher) {
+fn copy_chunk_to_slow_hdd(c: &mut Criterion) {
     let rt = rt();
-    b.iter(|| {
-        let task = || async {
-            let mut source = ChunkReader::new(CHUNK_SIZE, READ_SERVICE_PERIOD).take(SOURCE_SIZE);
-            let mut dest = SlowHddWriter::new(WRITE_SERVICE_PERIOD, WRITE_BUFFER);
-            copy(&mut source, &mut dest).await.unwrap();
-        };
 
-        rt.block_on(task());
-    })
+    c.bench_function("copy_chunk_to_slow_hdd", |b| {
+        b.iter(|| {
+            let task = || async {
+                let mut source =
+                    ChunkReader::new(CHUNK_SIZE, READ_SERVICE_PERIOD).take(SOURCE_SIZE);
+                let mut dest = SlowHddWriter::new(WRITE_SERVICE_PERIOD, WRITE_BUFFER);
+                copy(&mut source, &mut dest).await.unwrap();
+            };
+
+            rt.block_on(task());
+        })
+    });
 }
 
-benchmark_group!(
+criterion_group!(
     copy_bench,
     copy_mem_to_mem,
     copy_mem_to_slow_hdd,
     copy_chunk_to_mem,
     copy_chunk_to_slow_hdd,
 );
-benchmark_main!(copy_bench);
+criterion_main!(copy_bench);

benches/fs.rs

@@ -6,7 +6,7 @@ use tokio::fs::File;
 use tokio::io::AsyncReadExt;
 use tokio_util::codec::{BytesCodec, FramedRead /*FramedWrite*/};
 
-use bencher::{benchmark_group, benchmark_main, Bencher};
+use criterion::{criterion_group, criterion_main, Criterion};
 
 use std::fs::File as StdFile;
 use std::io::Read as StdRead;
@@ -23,81 +23,90 @@ const BLOCK_COUNT: usize = 1_000;
 const BUFFER_SIZE: usize = 4096;
 const DEV_ZERO: &str = "/dev/zero";
 
-fn async_read_codec(b: &mut Bencher) {
+fn async_read_codec(c: &mut Criterion) {
     let rt = rt();
 
-    b.iter(|| {
-        let task = || async {
-            let file = File::open(DEV_ZERO).await.unwrap();
-            let mut input_stream = FramedRead::with_capacity(file, BytesCodec::new(), BUFFER_SIZE);
+    c.bench_function("async_read_codec", |b| {
+        b.iter(|| {
+            let task = || async {
+                let file = File::open(DEV_ZERO).await.unwrap();
+                let mut input_stream =
+                    FramedRead::with_capacity(file, BytesCodec::new(), BUFFER_SIZE);
 
-            for _i in 0..BLOCK_COUNT {
-                let _bytes = input_stream.next().await.unwrap();
-            }
-        };
-
-        rt.block_on(task());
-    });
-}
-
-fn async_read_buf(b: &mut Bencher) {
-    let rt = rt();
-
-    b.iter(|| {
-        let task = || async {
-            let mut file = File::open(DEV_ZERO).await.unwrap();
-            let mut buffer = [0u8; BUFFER_SIZE];
-
-            for _i in 0..BLOCK_COUNT {
-                let count = file.read(&mut buffer).await.unwrap();
-                if count == 0 {
-                    break;
+                for _i in 0..BLOCK_COUNT {
+                    let _bytes = input_stream.next().await.unwrap();
                 }
-            }
-        };
+            };
 
-        rt.block_on(task());
+            rt.block_on(task());
+        })
     });
 }
 
-fn async_read_std_file(b: &mut Bencher) {
+fn async_read_buf(c: &mut Criterion) {
     let rt = rt();
 
-    let task = || async {
-        let mut file = tokio::task::block_in_place(|| Box::pin(StdFile::open(DEV_ZERO).unwrap()));
+    c.bench_function("async_read_buf", |b| {
+        b.iter(|| {
+            let task = || async {
+                let mut file = File::open(DEV_ZERO).await.unwrap();
+                let mut buffer = [0u8; BUFFER_SIZE];
 
-        for _i in 0..BLOCK_COUNT {
+                for _i in 0..BLOCK_COUNT {
+                    let count = file.read(&mut buffer).await.unwrap();
+                    if count == 0 {
+                        break;
+                    }
+                }
+            };
+
+            rt.block_on(task());
+        });
+    });
+}
+
+fn async_read_std_file(c: &mut Criterion) {
+    let rt = rt();
+
+    c.bench_function("async_read_std_file", |b| {
+        b.iter(|| {
+            let task = || async {
+                let mut file =
+                    tokio::task::block_in_place(|| Box::pin(StdFile::open(DEV_ZERO).unwrap()));
+
+                for _i in 0..BLOCK_COUNT {
+                    let mut buffer = [0u8; BUFFER_SIZE];
+                    let mut file_ref = file.as_mut();
+
+                    tokio::task::block_in_place(move || {
+                        file_ref.read_exact(&mut buffer).unwrap();
+                    });
+                }
+            };
+
+            rt.block_on(task());
+        });
+    });
+}
+
+fn sync_read(c: &mut Criterion) {
+    c.bench_function("sync_read", |b| {
+        b.iter(|| {
+            let mut file = StdFile::open(DEV_ZERO).unwrap();
             let mut buffer = [0u8; BUFFER_SIZE];
-            let mut file_ref = file.as_mut();
 
-            tokio::task::block_in_place(move || {
-                file_ref.read_exact(&mut buffer).unwrap();
-            });
-        }
-    };
-
-    b.iter(|| {
-        rt.block_on(task());
+            for _i in 0..BLOCK_COUNT {
+                file.read_exact(&mut buffer).unwrap();
+            }
+        })
     });
 }
 
-fn sync_read(b: &mut Bencher) {
-    b.iter(|| {
-        let mut file = StdFile::open(DEV_ZERO).unwrap();
-        let mut buffer = [0u8; BUFFER_SIZE];
-
-        for _i in 0..BLOCK_COUNT {
-            file.read_exact(&mut buffer).unwrap();
-        }
-    });
-}
-
-benchmark_group!(
+criterion_group!(
     file,
     async_read_std_file,
     async_read_buf,
     async_read_codec,
     sync_read
 );
-
-benchmark_main!(file);
+criterion_main!(file);

benches/rt_current_thread.rs

@@ -0,0 +1,89 @@
+//! Benchmark implementation details of the threaded scheduler. These benches are
+//! intended to be used as a form of regression testing and not as a general
+//! purpose benchmark demonstrating real-world performance.
+
+use tokio::runtime::{self, Runtime};
+
+use criterion::{criterion_group, criterion_main, Criterion};
+
+const NUM_SPAWN: usize = 1_000;
+
+fn rt_curr_spawn_many_local(c: &mut Criterion) {
+    let rt = rt();
+    let mut handles = Vec::with_capacity(NUM_SPAWN);
+
+    c.bench_function("spawn_many_local", |b| {
+        b.iter(|| {
+            rt.block_on(async {
+                for _ in 0..NUM_SPAWN {
+                    handles.push(tokio::spawn(async move {}));
+                }
+
+                for handle in handles.drain(..) {
+                    handle.await.unwrap();
+                }
+            });
+        })
+    });
+}
+
+fn rt_curr_spawn_many_remote_idle(c: &mut Criterion) {
+    let rt = rt();
+    let rt_handle = rt.handle();
+    let mut handles = Vec::with_capacity(NUM_SPAWN);
+
+    c.bench_function("spawn_many_remote_idle", |b| {
+        b.iter(|| {
+            for _ in 0..NUM_SPAWN {
+                handles.push(rt_handle.spawn(async {}));
+            }
+
+            rt.block_on(async {
+                for handle in handles.drain(..) {
+                    handle.await.unwrap();
+                }
+            });
+        })
+    });
+}
+
+fn rt_curr_spawn_many_remote_busy(c: &mut Criterion) {
+    let rt = rt();
+    let rt_handle = rt.handle();
+    let mut handles = Vec::with_capacity(NUM_SPAWN);
+
+    rt.spawn(async {
+        fn iter() {
+            tokio::spawn(async { iter() });
+        }
+
+        iter()
+    });
+
+    c.bench_function("spawn_many_remote_busy", |b| {
+        b.iter(|| {
+            for _ in 0..NUM_SPAWN {
+                handles.push(rt_handle.spawn(async {}));
+            }
+
+            rt.block_on(async {
+                for handle in handles.drain(..) {
+                    handle.await.unwrap();
+                }
+            });
+        })
+    });
+}
+
+fn rt() -> Runtime {
+    runtime::Builder::new_current_thread().build().unwrap()
+}
+
+criterion_group!(
+    rt_curr_scheduler,
+    rt_curr_spawn_many_local,
+    rt_curr_spawn_many_remote_idle,
+    rt_curr_spawn_many_remote_busy
+);
+
+criterion_main!(rt_curr_scheduler);

benches/rt_multi_threaded.rs

@@ -5,67 +5,173 @@
 use tokio::runtime::{self, Runtime};
 use tokio::sync::oneshot;
 
-use bencher::{benchmark_group, benchmark_main, Bencher};
-use std::sync::atomic::AtomicUsize;
 use std::sync::atomic::Ordering::Relaxed;
+use std::sync::atomic::{AtomicBool, AtomicUsize};
 use std::sync::{mpsc, Arc};
+use std::time::{Duration, Instant};
 
-fn spawn_many(b: &mut Bencher) {
-    const NUM_SPAWN: usize = 10_000;
+use criterion::{criterion_group, criterion_main, Criterion};
 
+const NUM_WORKERS: usize = 4;
+const NUM_SPAWN: usize = 10_000;
+const STALL_DUR: Duration = Duration::from_micros(10);
+
+fn rt_multi_spawn_many_local(c: &mut Criterion) {
     let rt = rt();
 
     let (tx, rx) = mpsc::sync_channel(1000);
     let rem = Arc::new(AtomicUsize::new(0));
 
-    b.iter(|| {
-        rem.store(NUM_SPAWN, Relaxed);
+    c.bench_function("spawn_many_local", |b| {
+        b.iter(|| {
+            rem.store(NUM_SPAWN, Relaxed);
 
-        rt.block_on(async {
-            for _ in 0..NUM_SPAWN {
-                let tx = tx.clone();
-                let rem = rem.clone();
+            rt.block_on(async {
+                for _ in 0..NUM_SPAWN {
+                    let tx = tx.clone();
+                    let rem = rem.clone();
 
-                tokio::spawn(async move {
-                    if 1 == rem.fetch_sub(1, Relaxed) {
-                        tx.send(()).unwrap();
-                    }
-                });
-            }
+                    tokio::spawn(async move {
+                        if 1 == rem.fetch_sub(1, Relaxed) {
+                            tx.send(()).unwrap();
+                        }
+                    });
+                }
 
-            let _ = rx.recv().unwrap();
-        });
+                rx.recv().unwrap();
+            });
+        })
     });
 }
 
-fn yield_many(b: &mut Bencher) {
+fn rt_multi_spawn_many_remote_idle(c: &mut Criterion) {
+    let rt = rt();
+
+    let mut handles = Vec::with_capacity(NUM_SPAWN);
+
+    c.bench_function("spawn_many_remote_idle", |b| {
+        b.iter(|| {
+            for _ in 0..NUM_SPAWN {
+                handles.push(rt.spawn(async {}));
+            }
+
+            rt.block_on(async {
+                for handle in handles.drain(..) {
+                    handle.await.unwrap();
+                }
+            });
+        })
+    });
+}
+
+// The runtime is busy with tasks that consume CPU time and yield. Yielding is a
+// lower notification priority than spawning / regular notification.
+fn rt_multi_spawn_many_remote_busy1(c: &mut Criterion) {
+    let rt = rt();
+    let rt_handle = rt.handle();
+    let mut handles = Vec::with_capacity(NUM_SPAWN);
+    let flag = Arc::new(AtomicBool::new(true));
+
+    // Spawn some tasks to keep the runtimes busy
+    for _ in 0..(2 * NUM_WORKERS) {
+        let flag = flag.clone();
+        rt.spawn(async move {
+            while flag.load(Relaxed) {
+                tokio::task::yield_now().await;
+                stall();
+            }
+        });
+    }
+
+    c.bench_function("spawn_many_remote_busy1", |b| {
+        b.iter(|| {
+            for _ in 0..NUM_SPAWN {
+                handles.push(rt_handle.spawn(async {}));
+            }
+
+            rt.block_on(async {
+                for handle in handles.drain(..) {
+                    handle.await.unwrap();
+                }
+            });
+        })
+    });
+
+    flag.store(false, Relaxed);
+}
+
+// The runtime is busy with tasks that consume CPU time and spawn new high-CPU
+// tasks. Spawning goes via a higher notification priority than yielding.
+fn rt_multi_spawn_many_remote_busy2(c: &mut Criterion) {
+    const NUM_SPAWN: usize = 1_000;
+
+    let rt = rt();
+    let rt_handle = rt.handle();
+    let mut handles = Vec::with_capacity(NUM_SPAWN);
+    let flag = Arc::new(AtomicBool::new(true));
+
+    // Spawn some tasks to keep the runtimes busy
+    for _ in 0..(NUM_WORKERS) {
+        let flag = flag.clone();
+        fn iter(flag: Arc<AtomicBool>) {
+            tokio::spawn(async {
+                if flag.load(Relaxed) {
+                    stall();
+                    iter(flag);
+                }
+            });
+        }
+        rt.spawn(async {
+            iter(flag);
+        });
+    }
+
+    c.bench_function("spawn_many_remote_busy2", |b| {
+        b.iter(|| {
+            for _ in 0..NUM_SPAWN {
+                handles.push(rt_handle.spawn(async {}));
+            }
+
+            rt.block_on(async {
+                for handle in handles.drain(..) {
+                    handle.await.unwrap();
+                }
+            });
+        })
+    });
+
+    flag.store(false, Relaxed);
+}
+
+fn rt_multi_yield_many(c: &mut Criterion) {
     const NUM_YIELD: usize = 1_000;
     const TASKS: usize = 200;
 
-    let rt = rt();
+    c.bench_function("yield_many", |b| {
+        let rt = rt();
+        let (tx, rx) = mpsc::sync_channel(TASKS);
 
-    let (tx, rx) = mpsc::sync_channel(TASKS);
+        b.iter(move || {
+            for _ in 0..TASKS {
+                let tx = tx.clone();
 
-    b.iter(move || {
-        for _ in 0..TASKS {
-            let tx = tx.clone();
+                rt.spawn(async move {
+                    for _ in 0..NUM_YIELD {
+                        tokio::task::yield_now().await;
+                    }
 
-            rt.spawn(async move {
-                for _ in 0..NUM_YIELD {
-                    tokio::task::yield_now().await;
-                }
+                    tx.send(()).unwrap();
+                });
+            }
 
-                tx.send(()).unwrap();
-            });
-        }
-
-        for _ in 0..TASKS {
-            let _ = rx.recv().unwrap();
-        }
+            for _ in 0..TASKS {
+                rx.recv().unwrap();
+            }
+        })
     });
 }
 
-fn ping_pong(b: &mut Bencher) {
+fn rt_multi_ping_pong(c: &mut Criterion) {
     const NUM_PINGS: usize = 1_000;
 
     let rt = rt();
@@ -73,46 +179,46 @@ fn ping_pong(b: &mut Bencher) {
     let (done_tx, done_rx) = mpsc::sync_channel(1000);
     let rem = Arc::new(AtomicUsize::new(0));
 
-    b.iter(|| {
-        let done_tx = done_tx.clone();
-        let rem = rem.clone();
-        rem.store(NUM_PINGS, Relaxed);
+    c.bench_function("ping_pong", |b| {
+        b.iter(|| {
+            let done_tx = done_tx.clone();
+            let rem = rem.clone();
+            rem.store(NUM_PINGS, Relaxed);
 
-        rt.block_on(async {
-            tokio::spawn(async move {
-                for _ in 0..NUM_PINGS {
-                    let rem = rem.clone();
-                    let done_tx = done_tx.clone();
-
-                    tokio::spawn(async move {
-                        let (tx1, rx1) = oneshot::channel();
-                        let (tx2, rx2) = oneshot::channel();
+            rt.block_on(async {
+                tokio::spawn(async move {
+                    for _ in 0..NUM_PINGS {
+                        let rem = rem.clone();
+                        let done_tx = done_tx.clone();
 
                         tokio::spawn(async move {
-                            rx1.await.unwrap();
-                            tx2.send(()).unwrap();
+                            let (tx1, rx1) = oneshot::channel();
+                            let (tx2, rx2) = oneshot::channel();
+
+                            tokio::spawn(async move {
+                                rx1.await.unwrap();
+                                tx2.send(()).unwrap();
+                            });
+
+                            tx1.send(()).unwrap();
+                            rx2.await.unwrap();
+
+                            if 1 == rem.fetch_sub(1, Relaxed) {
+                                done_tx.send(()).unwrap();
+                            }
                         });
+                    }
+                });
 
-                        tx1.send(()).unwrap();
-                        rx2.await.unwrap();
-
-                        if 1 == rem.fetch_sub(1, Relaxed) {
-                            done_tx.send(()).unwrap();
-                        }
-                    });
-                }
+                done_rx.recv().unwrap();
             });
-
-            done_rx.recv().unwrap();
-        });
+        })
     });
 }
 
-fn chained_spawn(b: &mut Bencher) {
+fn rt_multi_chained_spawn(c: &mut Criterion) {
     const ITER: usize = 1_000;
 
-    let rt = rt();
-
     fn iter(done_tx: mpsc::SyncSender<()>, n: usize) {
         if n == 0 {
             done_tx.send(()).unwrap();
@@ -123,29 +229,48 @@ fn chained_spawn(b: &mut Bencher) {
         }
     }
 
-    let (done_tx, done_rx) = mpsc::sync_channel(1000);
+    c.bench_function("chained_spawn", |b| {
+        let rt = rt();
+        let (done_tx, done_rx) = mpsc::sync_channel(1000);
 
-    b.iter(move || {
-        let done_tx = done_tx.clone();
+        b.iter(move || {
+            let done_tx = done_tx.clone();
 
-        rt.block_on(async {
-            tokio::spawn(async move {
-                iter(done_tx, ITER);
+            rt.block_on(async {
+                tokio::spawn(async move {
+                    iter(done_tx, ITER);
+                });
+
+                done_rx.recv().unwrap();
             });
-
-            done_rx.recv().unwrap();
-        });
+        })
     });
 }
 
 fn rt() -> Runtime {
     runtime::Builder::new_multi_thread()
-        .worker_threads(4)
+        .worker_threads(NUM_WORKERS)
         .enable_all()
         .build()
         .unwrap()
 }
 
-benchmark_group!(scheduler, spawn_many, ping_pong, yield_many, chained_spawn,);
+fn stall() {
+    let now = Instant::now();
+    while now.elapsed() < STALL_DUR {
+        std::thread::yield_now();
+    }
+}
 
-benchmark_main!(scheduler);
+criterion_group!(
+    rt_multi_scheduler,
+    rt_multi_spawn_many_local,
+    rt_multi_spawn_many_remote_idle,
+    rt_multi_spawn_many_remote_busy1,
+    rt_multi_spawn_many_remote_busy2,
+    rt_multi_ping_pong,
+    rt_multi_yield_many,
+    rt_multi_chained_spawn,
+);
+
+criterion_main!(rt_multi_scheduler);

benches/signal.rs

@@ -1,7 +1,7 @@
 //! Benchmark the delay in propagating OS signals to any listeners.
 #![cfg(unix)]
 
-use bencher::{benchmark_group, benchmark_main, Bencher};
+use criterion::{criterion_group, criterion_main, Criterion};
 use std::future::Future;
 use std::pin::Pin;
 use std::task::{Context, Poll};
@@ -41,7 +41,7 @@ pub fn send_signal(signal: libc::c_int) {
     }
 }
 
-fn many_signals(bench: &mut Bencher) {
+fn many_signals(c: &mut Criterion) {
     let num_signals = 10;
     let (tx, mut rx) = mpsc::channel(num_signals);
 
@@ -75,21 +75,23 @@ fn many_signals(bench: &mut Bencher) {
     // tasks have been polled at least once
     rt.block_on(Spinner::new());
 
-    bench.iter(|| {
-        rt.block_on(async {
-            send_signal(libc::SIGCHLD);
-            for _ in 0..num_signals {
-                rx.recv().await.expect("channel closed");
-            }
+    c.bench_function("many_signals", |b| {
+        b.iter(|| {
+            rt.block_on(async {
+                send_signal(libc::SIGCHLD);
+                for _ in 0..num_signals {
+                    rx.recv().await.expect("channel closed");
+                }
 
-            send_signal(libc::SIGIO);
-            for _ in 0..num_signals {
-                rx.recv().await.expect("channel closed");
-            }
-        });
+                send_signal(libc::SIGIO);
+                for _ in 0..num_signals {
+                    rx.recv().await.expect("channel closed");
+                }
+            });
+        })
     });
 }
 
-benchmark_group!(signal_group, many_signals,);
+criterion_group!(signal_group, many_signals);
 
-benchmark_main!(signal_group);
+criterion_main!(signal_group);

benches/spawn.rs

@@ -2,10 +2,7 @@
 //! This essentially measure the time to enqueue a task in the local and remote
 //! case.
 
-#[macro_use]
-extern crate bencher;
-
-use bencher::{black_box, Bencher};
+use criterion::{black_box, criterion_group, criterion_main, Criterion};
 
 async fn work() -> usize {
     let val = 1 + 1;
@@ -13,67 +10,77 @@ async fn work() -> usize {
     black_box(val)
 }
 
-fn basic_scheduler_spawn(bench: &mut Bencher) {
+fn basic_scheduler_spawn(c: &mut Criterion) {
     let runtime = tokio::runtime::Builder::new_current_thread()
         .build()
         .unwrap();
-    bench.iter(|| {
-        runtime.block_on(async {
-            let h = tokio::spawn(work());
-            assert_eq!(h.await.unwrap(), 2);
-        });
+
+    c.bench_function("basic_scheduler_spawn", |b| {
+        b.iter(|| {
+            runtime.block_on(async {
+                let h = tokio::spawn(work());
+                assert_eq!(h.await.unwrap(), 2);
+            });
+        })
     });
 }
 
-fn basic_scheduler_spawn10(bench: &mut Bencher) {
+fn basic_scheduler_spawn10(c: &mut Criterion) {
     let runtime = tokio::runtime::Builder::new_current_thread()
         .build()
         .unwrap();
-    bench.iter(|| {
-        runtime.block_on(async {
-            let mut handles = Vec::with_capacity(10);
-            for _ in 0..10 {
-                handles.push(tokio::spawn(work()));
-            }
-            for handle in handles {
-                assert_eq!(handle.await.unwrap(), 2);
-            }
-        });
+
+    c.bench_function("basic_scheduler_spawn10", |b| {
+        b.iter(|| {
+            runtime.block_on(async {
+                let mut handles = Vec::with_capacity(10);
+                for _ in 0..10 {
+                    handles.push(tokio::spawn(work()));
+                }
+                for handle in handles {
+                    assert_eq!(handle.await.unwrap(), 2);
+                }
+            });
+        })
     });
 }
 
-fn threaded_scheduler_spawn(bench: &mut Bencher) {
+fn threaded_scheduler_spawn(c: &mut Criterion) {
     let runtime = tokio::runtime::Builder::new_multi_thread()
         .worker_threads(1)
         .build()
         .unwrap();
-    bench.iter(|| {
-        runtime.block_on(async {
-            let h = tokio::spawn(work());
-            assert_eq!(h.await.unwrap(), 2);
-        });
+    c.bench_function("threaded_scheduler_spawn", |b| {
+        b.iter(|| {
+            runtime.block_on(async {
+                let h = tokio::spawn(work());
+                assert_eq!(h.await.unwrap(), 2);
+            });
+        })
     });
 }
 
-fn threaded_scheduler_spawn10(bench: &mut Bencher) {
+fn threaded_scheduler_spawn10(c: &mut Criterion) {
     let runtime = tokio::runtime::Builder::new_multi_thread()
         .worker_threads(1)
         .build()
         .unwrap();
-    bench.iter(|| {
-        runtime.block_on(async {
-            let mut handles = Vec::with_capacity(10);
-            for _ in 0..10 {
-                handles.push(tokio::spawn(work()));
-            }
-            for handle in handles {
-                assert_eq!(handle.await.unwrap(), 2);
-            }
-        });
+    c.bench_function("threaded_scheduler_spawn10", |b| {
+        b.iter(|| {
+            runtime.block_on(async {
+                let mut handles = Vec::with_capacity(10);
+                for _ in 0..10 {
+                    handles.push(tokio::spawn(work()));
+                }
+                for handle in handles {
+                    assert_eq!(handle.await.unwrap(), 2);
+                }
+            });
+        })
     });
 }
 
-bencher::benchmark_group!(
+criterion_group!(
     spawn,
     basic_scheduler_spawn,
     basic_scheduler_spawn10,
@@ -81,4 +88,4 @@ bencher::benchmark_group!(
     threaded_scheduler_spawn10,
 );
 
-bencher::benchmark_main!(spawn);
+criterion_main!(spawn);

benches/sync_broadcast.rs

@@ -0,0 +1,82 @@
+use rand::{Rng, RngCore, SeedableRng};
+use std::sync::atomic::{AtomicUsize, Ordering};
+use std::sync::Arc;
+use tokio::sync::{broadcast, Notify};
+
+use criterion::measurement::WallTime;
+use criterion::{black_box, criterion_group, criterion_main, BenchmarkGroup, Criterion};
+
+fn rt() -> tokio::runtime::Runtime {
+    tokio::runtime::Builder::new_multi_thread()
+        .worker_threads(6)
+        .build()
+        .unwrap()
+}
+
+fn do_work(rng: &mut impl RngCore) -> u32 {
+    use std::fmt::Write;
+    let mut message = String::new();
+    for i in 1..=10 {
+        let _ = write!(&mut message, " {i}={}", rng.gen::<f64>());
+    }
+    message
+        .as_bytes()
+        .iter()
+        .map(|&c| c as u32)
+        .fold(0, u32::wrapping_add)
+}
+
+fn contention_impl<const N_TASKS: usize>(g: &mut BenchmarkGroup<WallTime>) {
+    let rt = rt();
+
+    let (tx, _rx) = broadcast::channel::<usize>(1000);
+    let wg = Arc::new((AtomicUsize::new(0), Notify::new()));
+
+    for n in 0..N_TASKS {
+        let wg = wg.clone();
+        let mut rx = tx.subscribe();
+        let mut rng = rand::rngs::StdRng::seed_from_u64(n as u64);
+        rt.spawn(async move {
+            while (rx.recv().await).is_ok() {
+                let r = do_work(&mut rng);
+                let _ = black_box(r);
+                if wg.0.fetch_sub(1, Ordering::Relaxed) == 1 {
+                    wg.1.notify_one();
+                }
+            }
+        });
+    }
+
+    const N_ITERS: usize = 100;
+
+    g.bench_function(N_TASKS.to_string(), |b| {
+        b.iter(|| {
+            rt.block_on({
+                let wg = wg.clone();
+                let tx = tx.clone();
+                async move {
+                    for i in 0..N_ITERS {
+                        assert_eq!(wg.0.fetch_add(N_TASKS, Ordering::Relaxed), 0);
+                        tx.send(i).unwrap();
+                        while wg.0.load(Ordering::Relaxed) > 0 {
+                            wg.1.notified().await;
+                        }
+                    }
+                }
+            })
+        })
+    });
+}
+
+fn bench_contention(c: &mut Criterion) {
+    let mut group = c.benchmark_group("contention");
+    contention_impl::<10>(&mut group);
+    contention_impl::<100>(&mut group);
+    contention_impl::<500>(&mut group);
+    contention_impl::<1000>(&mut group);
+    group.finish();
+}
+
+criterion_group!(contention, bench_contention);
+
+criterion_main!(contention);

benches/sync_mpsc.rs

@@ -1,8 +1,23 @@
-use bencher::{black_box, Bencher};
 use tokio::sync::mpsc;
 
-type Medium = [usize; 64];
-type Large = [Medium; 64];
+use criterion::measurement::WallTime;
+use criterion::{black_box, criterion_group, criterion_main, BenchmarkGroup, Criterion};
+
+#[derive(Debug, Copy, Clone)]
+struct Medium(#[allow(dead_code)] [usize; 64]);
+impl Default for Medium {
+    fn default() -> Self {
+        Medium([0; 64])
+    }
+}
+
+#[derive(Debug, Copy, Clone)]
+struct Large(#[allow(dead_code)] [Medium; 64]);
+impl Default for Large {
+    fn default() -> Self {
+        Large([Medium::default(); 64])
+    }
+}
 
 fn rt() -> tokio::runtime::Runtime {
     tokio::runtime::Builder::new_multi_thread()
@@ -11,169 +26,306 @@ fn rt() -> tokio::runtime::Runtime {
         .unwrap()
 }
 
-fn create_1_medium(b: &mut Bencher) {
-    b.iter(|| {
-        black_box(&mpsc::channel::<Medium>(1));
-    });
-}
-
-fn create_100_medium(b: &mut Bencher) {
-    b.iter(|| {
-        black_box(&mpsc::channel::<Medium>(100));
-    });
-}
-
-fn create_100_000_medium(b: &mut Bencher) {
-    b.iter(|| {
-        black_box(&mpsc::channel::<Medium>(100_000));
-    });
-}
-
-fn send_medium(b: &mut Bencher) {
-    let rt = rt();
-
-    b.iter(|| {
-        let (tx, mut rx) = mpsc::channel::<Medium>(1000);
-
-        let _ = rt.block_on(tx.send([0; 64]));
-
-        rt.block_on(rx.recv()).unwrap();
-    });
-}
-
-fn send_large(b: &mut Bencher) {
-    let rt = rt();
-
-    b.iter(|| {
-        let (tx, mut rx) = mpsc::channel::<Large>(1000);
-
-        let _ = rt.block_on(tx.send([[0; 64]; 64]));
-
-        rt.block_on(rx.recv()).unwrap();
-    });
-}
-
-fn contention_bounded(b: &mut Bencher) {
-    let rt = rt();
-
-    b.iter(|| {
-        rt.block_on(async move {
-            let (tx, mut rx) = mpsc::channel::<usize>(1_000_000);
-
-            for _ in 0..5 {
-                let tx = tx.clone();
-                tokio::spawn(async move {
-                    for i in 0..1000 {
-                        tx.send(i).await.unwrap();
-                    }
-                });
-            }
-
-            for _ in 0..1_000 * 5 {
-                let _ = rx.recv().await;
-            }
+fn create_medium<const SIZE: usize>(g: &mut BenchmarkGroup<WallTime>) {
+    g.bench_function(SIZE.to_string(), |b| {
+        b.iter(|| {
+            black_box(&mpsc::channel::<Medium>(SIZE));
         })
     });
 }
 
-fn contention_bounded_full(b: &mut Bencher) {
+fn send_data<T: Default, const SIZE: usize>(g: &mut BenchmarkGroup<WallTime>, prefix: &str) {
     let rt = rt();
 
-    b.iter(|| {
-        rt.block_on(async move {
-            let (tx, mut rx) = mpsc::channel::<usize>(100);
+    g.bench_function(format!("{}_{}", prefix, SIZE), |b| {
+        b.iter(|| {
+            let (tx, mut rx) = mpsc::channel::<T>(SIZE);
 
-            for _ in 0..5 {
-                let tx = tx.clone();
-                tokio::spawn(async move {
-                    for i in 0..1000 {
-                        tx.send(i).await.unwrap();
-                    }
-                });
-            }
+            let _ = rt.block_on(tx.send(T::default()));
 
-            for _ in 0..1_000 * 5 {
-                let _ = rx.recv().await;
-            }
+            rt.block_on(rx.recv()).unwrap();
         })
     });
 }
 
-fn contention_unbounded(b: &mut Bencher) {
+fn contention_bounded(g: &mut BenchmarkGroup<WallTime>) {
     let rt = rt();
 
-    b.iter(|| {
-        rt.block_on(async move {
-            let (tx, mut rx) = mpsc::unbounded_channel::<usize>();
+    g.bench_function("bounded", |b| {
+        b.iter(|| {
+            rt.block_on(async move {
+                let (tx, mut rx) = mpsc::channel::<usize>(1_000_000);
 
-            for _ in 0..5 {
-                let tx = tx.clone();
-                tokio::spawn(async move {
-                    for i in 0..1000 {
-                        tx.send(i).unwrap();
-                    }
-                });
-            }
+                for _ in 0..5 {
+                    let tx = tx.clone();
+                    tokio::spawn(async move {
+                        for i in 0..1000 {
+                            tx.send(i).await.unwrap();
+                        }
+                    });
+                }
 
-            for _ in 0..1_000 * 5 {
-                let _ = rx.recv().await;
-            }
+                for _ in 0..1_000 * 5 {
+                    let _ = rx.recv().await;
+                }
+            })
         })
     });
 }
 
-fn uncontented_bounded(b: &mut Bencher) {
+fn contention_bounded_recv_many(g: &mut BenchmarkGroup<WallTime>) {
     let rt = rt();
 
-    b.iter(|| {
-        rt.block_on(async move {
-            let (tx, mut rx) = mpsc::channel::<usize>(1_000_000);
+    g.bench_function("bounded_recv_many", |b| {
+        b.iter(|| {
+            rt.block_on(async move {
+                let (tx, mut rx) = mpsc::channel::<usize>(1_000_000);
 
-            for i in 0..5000 {
-                tx.send(i).await.unwrap();
-            }
+                for _ in 0..5 {
+                    let tx = tx.clone();
+                    tokio::spawn(async move {
+                        for i in 0..1000 {
+                            tx.send(i).await.unwrap();
+                        }
+                    });
+                }
 
-            for _ in 0..5_000 {
-                let _ = rx.recv().await;
-            }
+                let mut buffer = Vec::<usize>::with_capacity(5_000);
+                let mut total = 0;
+                while total < 1_000 * 5 {
+                    total += rx.recv_many(&mut buffer, 5_000).await;
+                }
+            })
         })
     });
 }
 
-fn uncontented_unbounded(b: &mut Bencher) {
+fn contention_bounded_full(g: &mut BenchmarkGroup<WallTime>) {
     let rt = rt();
 
-    b.iter(|| {
-        rt.block_on(async move {
-            let (tx, mut rx) = mpsc::unbounded_channel::<usize>();
+    g.bench_function("bounded_full", |b| {
+        b.iter(|| {
+            rt.block_on(async move {
+                let (tx, mut rx) = mpsc::channel::<usize>(100);
 
-            for i in 0..5000 {
-                tx.send(i).unwrap();
-            }
+                for _ in 0..5 {
+                    let tx = tx.clone();
+                    tokio::spawn(async move {
+                        for i in 0..1000 {
+                            tx.send(i).await.unwrap();
+                        }
+                    });
+                }
 
-            for _ in 0..5_000 {
-                let _ = rx.recv().await;
-            }
+                for _ in 0..1_000 * 5 {
+                    let _ = rx.recv().await;
+                }
+            })
         })
     });
 }
 
-bencher::benchmark_group!(
-    create,
-    create_1_medium,
-    create_100_medium,
-    create_100_000_medium
-);
+fn contention_bounded_full_recv_many(g: &mut BenchmarkGroup<WallTime>) {
+    let rt = rt();
 
-bencher::benchmark_group!(send, send_medium, send_large);
+    g.bench_function("bounded_full_recv_many", |b| {
+        b.iter(|| {
+            rt.block_on(async move {
+                let (tx, mut rx) = mpsc::channel::<usize>(100);
 
-bencher::benchmark_group!(
-    contention,
-    contention_bounded,
-    contention_bounded_full,
-    contention_unbounded,
-    uncontented_bounded,
-    uncontented_unbounded
-);
+                for _ in 0..5 {
+                    let tx = tx.clone();
+                    tokio::spawn(async move {
+                        for i in 0..1000 {
+                            tx.send(i).await.unwrap();
+                        }
+                    });
+                }
 
-bencher::benchmark_main!(create, send, contention);
+                let mut buffer = Vec::<usize>::with_capacity(5_000);
+                let mut total = 0;
+                while total < 1_000 * 5 {
+                    total += rx.recv_many(&mut buffer, 5_000).await;
+                }
+            })
+        })
+    });
+}
+
+fn contention_unbounded(g: &mut BenchmarkGroup<WallTime>) {
+    let rt = rt();
+
+    g.bench_function("unbounded", |b| {
+        b.iter(|| {
+            rt.block_on(async move {
+                let (tx, mut rx) = mpsc::unbounded_channel::<usize>();
+
+                for _ in 0..5 {
+                    let tx = tx.clone();
+                    tokio::spawn(async move {
+                        for i in 0..1000 {
+                            tx.send(i).unwrap();
+                        }
+                    });
+                }
+
+                for _ in 0..1_000 * 5 {
+                    let _ = rx.recv().await;
+                }
+            })
+        })
+    });
+}
+
+fn contention_unbounded_recv_many(g: &mut BenchmarkGroup<WallTime>) {
+    let rt = rt();
+
+    g.bench_function("unbounded_recv_many", |b| {
+        b.iter(|| {
+            rt.block_on(async move {
+                let (tx, mut rx) = mpsc::unbounded_channel::<usize>();
+
+                for _ in 0..5 {
+                    let tx = tx.clone();
+                    tokio::spawn(async move {
+                        for i in 0..1000 {
+                            tx.send(i).unwrap();
+                        }
+                    });
+                }
+
+                let mut buffer = Vec::<usize>::with_capacity(5_000);
+                let mut total = 0;
+                while total < 1_000 * 5 {
+                    total += rx.recv_many(&mut buffer, 5_000).await;
+                }
+            })
+        })
+    });
+}
+
+fn uncontented_bounded(g: &mut BenchmarkGroup<WallTime>) {
+    let rt = rt();
+
+    g.bench_function("bounded", |b| {
+        b.iter(|| {
+            rt.block_on(async move {
+                let (tx, mut rx) = mpsc::channel::<usize>(1_000_000);
+
+                for i in 0..5000 {
+                    tx.send(i).await.unwrap();
+                }
+
+                for _ in 0..5_000 {
+                    let _ = rx.recv().await;
+                }
+            })
+        })
+    });
+}
+
+fn uncontented_bounded_recv_many(g: &mut BenchmarkGroup<WallTime>) {
+    let rt = rt();
+
+    g.bench_function("bounded_recv_many", |b| {
+        b.iter(|| {
+            rt.block_on(async move {
+                let (tx, mut rx) = mpsc::channel::<usize>(1_000_000);
+
+                for i in 0..5000 {
+                    tx.send(i).await.unwrap();
+                }
+
+                let mut buffer = Vec::<usize>::with_capacity(5_000);
+                let mut total = 0;
+                while total < 1_000 * 5 {
+                    total += rx.recv_many(&mut buffer, 5_000).await;
+                }
+            })
+        })
+    });
+}
+
+fn uncontented_unbounded(g: &mut BenchmarkGroup<WallTime>) {
+    let rt = rt();
+
+    g.bench_function("unbounded", |b| {
+        b.iter(|| {
+            rt.block_on(async move {
+                let (tx, mut rx) = mpsc::unbounded_channel::<usize>();
+
+                for i in 0..5000 {
+                    tx.send(i).unwrap();
+                }
+
+                for _ in 0..5_000 {
+                    let _ = rx.recv().await;
+                }
+            })
+        })
+    });
+}
+
+fn uncontented_unbounded_recv_many(g: &mut BenchmarkGroup<WallTime>) {
+    let rt = rt();
+
+    g.bench_function("unbounded_recv_many", |b| {
+        b.iter(|| {
+            rt.block_on(async move {
+                let (tx, mut rx) = mpsc::unbounded_channel::<usize>();
+
+                for i in 0..5000 {
+                    tx.send(i).unwrap();
+                }
+
+                let mut buffer = Vec::<usize>::with_capacity(5_000);
+                let mut total = 0;
+                while total < 1_000 * 5 {
+                    total += rx.recv_many(&mut buffer, 5_000).await;
+                }
+            })
+        })
+    });
+}
+
+fn bench_create_medium(c: &mut Criterion) {
+    let mut group = c.benchmark_group("create_medium");
+    create_medium::<1>(&mut group);
+    create_medium::<100>(&mut group);
+    create_medium::<100_000>(&mut group);
+    group.finish();
+}
+
+fn bench_send(c: &mut Criterion) {
+    let mut group = c.benchmark_group("send");
+    send_data::<Medium, 1000>(&mut group, "medium");
+    send_data::<Large, 1000>(&mut group, "large");
+    group.finish();
+}
+
+fn bench_contention(c: &mut Criterion) {
+    let mut group = c.benchmark_group("contention");
+    contention_bounded(&mut group);
+    contention_bounded_recv_many(&mut group);
+    contention_bounded_full(&mut group);
+    contention_bounded_full_recv_many(&mut group);
+    contention_unbounded(&mut group);
+    contention_unbounded_recv_many(&mut group);
+    group.finish();
+}
+
+fn bench_uncontented(c: &mut Criterion) {
+    let mut group = c.benchmark_group("uncontented");
+    uncontented_bounded(&mut group);
+    uncontented_bounded_recv_many(&mut group);
+    uncontented_unbounded(&mut group);
+    uncontented_unbounded_recv_many(&mut group);
+    group.finish();
+}
+
+criterion_group!(create, bench_create_medium);
+criterion_group!(send, bench_send);
+criterion_group!(contention, bench_contention);
+criterion_group!(uncontented, bench_uncontented);
+
+criterion_main!(create, send, contention, uncontented);

benches/sync_mpsc_oneshot.rs

@@ -0,0 +1,56 @@
+use tokio::{
+    runtime::Runtime,
+    sync::{mpsc, oneshot},
+};
+
+use criterion::{criterion_group, criterion_main, Criterion};
+
+fn request_reply_current_thread(c: &mut Criterion) {
+    let rt = tokio::runtime::Builder::new_current_thread()
+        .build()
+        .unwrap();
+
+    request_reply(c, rt);
+}
+
+fn request_reply_multi_threaded(c: &mut Criterion) {
+    let rt = tokio::runtime::Builder::new_multi_thread()
+        .worker_threads(1)
+        .build()
+        .unwrap();
+
+    request_reply(c, rt);
+}
+
+fn request_reply(b: &mut Criterion, rt: Runtime) {
+    let tx = rt.block_on(async move {
+        let (tx, mut rx) = mpsc::channel::<oneshot::Sender<()>>(10);
+        tokio::spawn(async move {
+            while let Some(reply) = rx.recv().await {
+                reply.send(()).unwrap();
+            }
+        });
+        tx
+    });
+
+    b.bench_function("request_reply", |b| {
+        b.iter(|| {
+            let task_tx = tx.clone();
+            rt.block_on(async move {
+                for _ in 0..1_000 {
+                    let (o_tx, o_rx) = oneshot::channel();
+                    task_tx.send(o_tx).await.unwrap();
+                    let _ = o_rx.await;
+                }
+            })
+        })
+    });
+}
+
+criterion_group!(
+    sync_mpsc_oneshot_group,
+    request_reply_current_thread,
+    request_reply_multi_threaded,
+);
+
+criterion_main!(sync_mpsc_oneshot_group);

benches/sync_notify.rs

@@ -0,0 +1,104 @@
+use std::sync::atomic::{AtomicUsize, Ordering};
+use std::sync::Arc;
+
+use tokio::sync::Notify;
+
+use criterion::measurement::WallTime;
+use criterion::{criterion_group, criterion_main, BenchmarkGroup, Criterion};
+
+fn rt() -> tokio::runtime::Runtime {
+    tokio::runtime::Builder::new_multi_thread()
+        .worker_threads(6)
+        .build()
+        .unwrap()
+}
+
+fn notify_waiters<const N_WAITERS: usize>(g: &mut BenchmarkGroup<WallTime>) {
+    let rt = rt();
+    let notify = Arc::new(Notify::new());
+    let counter = Arc::new(AtomicUsize::new(0));
+    for _ in 0..N_WAITERS {
+        rt.spawn({
+            let notify = notify.clone();
+            let counter = counter.clone();
+            async move {
+                loop {
+                    notify.notified().await;
+                    counter.fetch_add(1, Ordering::Relaxed);
+                }
+            }
+        });
+    }
+
+    const N_ITERS: usize = 500;
+    g.bench_function(N_WAITERS.to_string(), |b| {
+        b.iter(|| {
+            counter.store(0, Ordering::Relaxed);
+            loop {
+                notify.notify_waiters();
+                if counter.load(Ordering::Relaxed) >= N_ITERS {
+                    break;
+                }
+            }
+        })
+    });
+}
+
+fn notify_one<const N_WAITERS: usize>(g: &mut BenchmarkGroup<WallTime>) {
+    let rt = rt();
+    let notify = Arc::new(Notify::new());
+    let counter = Arc::new(AtomicUsize::new(0));
+    for _ in 0..N_WAITERS {
+        rt.spawn({
+            let notify = notify.clone();
+            let counter = counter.clone();
+            async move {
+                loop {
+                    notify.notified().await;
+                    counter.fetch_add(1, Ordering::Relaxed);
+                }
+            }
+        });
+    }
+
+    const N_ITERS: usize = 500;
+    g.bench_function(N_WAITERS.to_string(), |b| {
+        b.iter(|| {
+            counter.store(0, Ordering::Relaxed);
+            loop {
+                notify.notify_one();
+                if counter.load(Ordering::Relaxed) >= N_ITERS {
+                    break;
+                }
+            }
+        })
+    });
+}
+
+fn bench_notify_one(c: &mut Criterion) {
+    let mut group = c.benchmark_group("notify_one");
+    notify_one::<10>(&mut group);
+    notify_one::<50>(&mut group);
+    notify_one::<100>(&mut group);
+    notify_one::<200>(&mut group);
+    notify_one::<500>(&mut group);
+    group.finish();
+}
+
+fn bench_notify_waiters(c: &mut Criterion) {
+    let mut group = c.benchmark_group("notify_waiters");
+    notify_waiters::<10>(&mut group);
+    notify_waiters::<50>(&mut group);
+    notify_waiters::<100>(&mut group);
+    notify_waiters::<200>(&mut group);
+    notify_waiters::<500>(&mut group);
+    group.finish();
+}
+
+criterion_group!(
+    notify_waiters_simple,
+    bench_notify_one,
+    bench_notify_waiters
+);
+
+criterion_main!(notify_waiters_simple);

benches/sync_rwlock.rs

@@ -1,26 +1,30 @@
-use bencher::{black_box, Bencher};
 use std::sync::Arc;
 use tokio::{sync::RwLock, task};
 
-fn read_uncontended(b: &mut Bencher) {
+use criterion::measurement::WallTime;
+use criterion::{black_box, criterion_group, criterion_main, BenchmarkGroup, Criterion};
+
+fn read_uncontended(g: &mut BenchmarkGroup<WallTime>) {
     let rt = tokio::runtime::Builder::new_multi_thread()
         .worker_threads(6)
         .build()
         .unwrap();
 
     let lock = Arc::new(RwLock::new(()));
-    b.iter(|| {
-        let lock = lock.clone();
-        rt.block_on(async move {
-            for _ in 0..6 {
-                let read = lock.read().await;
-                let _read = black_box(read);
-            }
+    g.bench_function("read", |b| {
+        b.iter(|| {
+            let lock = lock.clone();
+            rt.block_on(async move {
+                for _ in 0..6 {
+                    let read = lock.read().await;
+                    let _read = black_box(read);
+                }
+            })
         })
     });
 }
 
-fn read_concurrent_uncontended_multi(b: &mut Bencher) {
+fn read_concurrent_uncontended_multi(g: &mut BenchmarkGroup<WallTime>) {
     let rt = tokio::runtime::Builder::new_multi_thread()
         .worker_threads(6)
         .build()
@@ -32,23 +36,25 @@ fn read_concurrent_uncontended_multi(b: &mut Bencher) {
     }
 
     let lock = Arc::new(RwLock::new(()));
-    b.iter(|| {
-        let lock = lock.clone();
-        rt.block_on(async move {
-            let j = tokio::try_join! {
-                task::spawn(task(lock.clone())),
-                task::spawn(task(lock.clone())),
-                task::spawn(task(lock.clone())),
-                task::spawn(task(lock.clone())),
-                task::spawn(task(lock.clone())),
-                task::spawn(task(lock.clone()))
-            };
-            j.unwrap();
+    g.bench_function("read_concurrent_multi", |b| {
+        b.iter(|| {
+            let lock = lock.clone();
+            rt.block_on(async move {
+                let j = tokio::try_join! {
+                    task::spawn(task(lock.clone())),
+                    task::spawn(task(lock.clone())),
+                    task::spawn(task(lock.clone())),
+                    task::spawn(task(lock.clone())),
+                    task::spawn(task(lock.clone())),
+                    task::spawn(task(lock.clone()))
+                };
+                j.unwrap();
+            })
         })
     });
 }
 
-fn read_concurrent_uncontended(b: &mut Bencher) {
+fn read_concurrent_uncontended(g: &mut BenchmarkGroup<WallTime>) {
     let rt = tokio::runtime::Builder::new_current_thread()
         .build()
         .unwrap();
@@ -59,22 +65,24 @@ fn read_concurrent_uncontended(b: &mut Bencher) {
     }
 
     let lock = Arc::new(RwLock::new(()));
-    b.iter(|| {
-        let lock = lock.clone();
-        rt.block_on(async move {
-            tokio::join! {
-                task(lock.clone()),
-                task(lock.clone()),
-                task(lock.clone()),
-                task(lock.clone()),
-                task(lock.clone()),
-                task(lock.clone())
-            };
+    g.bench_function("read_concurrent", |b| {
+        b.iter(|| {
+            let lock = lock.clone();
+            rt.block_on(async move {
+                tokio::join! {
+                    task(lock.clone()),
+                    task(lock.clone()),
+                    task(lock.clone()),
+                    task(lock.clone()),
+                    task(lock.clone()),
+                    task(lock.clone())
+                };
+            })
         })
     });
 }
 
-fn read_concurrent_contended_multi(b: &mut Bencher) {
+fn read_concurrent_contended_multi(g: &mut BenchmarkGroup<WallTime>) {
     let rt = tokio::runtime::Builder::new_multi_thread()
         .worker_threads(6)
         .build()
@@ -86,24 +94,26 @@ fn read_concurrent_contended_multi(b: &mut Bencher) {
     }
 
     let lock = Arc::new(RwLock::new(()));
-    b.iter(|| {
-        let lock = lock.clone();
-        rt.block_on(async move {
-            let write = lock.write().await;
-            let j = tokio::try_join! {
-                async move { drop(write); Ok(()) },
-                task::spawn(task(lock.clone())),
-                task::spawn(task(lock.clone())),
-                task::spawn(task(lock.clone())),
-                task::spawn(task(lock.clone())),
-                task::spawn(task(lock.clone())),
-            };
-            j.unwrap();
+    g.bench_function("read_concurrent_multi", |b| {
+        b.iter(|| {
+            let lock = lock.clone();
+            rt.block_on(async move {
+                let write = lock.write().await;
+                let j = tokio::try_join! {
+                    async move { drop(write); Ok(()) },
+                    task::spawn(task(lock.clone())),
+                    task::spawn(task(lock.clone())),
+                    task::spawn(task(lock.clone())),
+                    task::spawn(task(lock.clone())),
+                    task::spawn(task(lock.clone())),
+                };
+                j.unwrap();
+            })
         })
     });
 }
 
-fn read_concurrent_contended(b: &mut Bencher) {
+fn read_concurrent_contended(g: &mut BenchmarkGroup<WallTime>) {
     let rt = tokio::runtime::Builder::new_current_thread()
         .build()
         .unwrap();
@@ -114,29 +124,40 @@ fn read_concurrent_contended(b: &mut Bencher) {
     }
 
     let lock = Arc::new(RwLock::new(()));
-    b.iter(|| {
-        let lock = lock.clone();
-        rt.block_on(async move {
-            let write = lock.write().await;
-            tokio::join! {
-                async move { drop(write) },
-                task(lock.clone()),
-                task(lock.clone()),
-                task(lock.clone()),
-                task(lock.clone()),
-                task(lock.clone()),
-            };
+    g.bench_function("read_concurrent", |b| {
+        b.iter(|| {
+            let lock = lock.clone();
+            rt.block_on(async move {
+                let write = lock.write().await;
+                tokio::join! {
+                    async move { drop(write) },
+                    task(lock.clone()),
+                    task(lock.clone()),
+                    task(lock.clone()),
+                    task(lock.clone()),
+                    task(lock.clone()),
+                };
+            })
         })
     });
 }
 
-bencher::benchmark_group!(
-    sync_rwlock,
-    read_uncontended,
-    read_concurrent_uncontended,
-    read_concurrent_uncontended_multi,
-    read_concurrent_contended,
-    read_concurrent_contended_multi
-);
+fn bench_contention(c: &mut Criterion) {
+    let mut group = c.benchmark_group("contention");
+    read_concurrent_contended(&mut group);
+    read_concurrent_contended_multi(&mut group);
+    group.finish();
+}
 
-bencher::benchmark_main!(sync_rwlock);
+fn bench_uncontented(c: &mut Criterion) {
+    let mut group = c.benchmark_group("uncontented");
+    read_uncontended(&mut group);
+    read_concurrent_uncontended(&mut group);
+    read_concurrent_uncontended_multi(&mut group);
+    group.finish();
+}
+
+criterion_group!(contention, bench_contention);
+criterion_group!(uncontented, bench_uncontented);
+
+criterion_main!(contention, uncontented);

benches/sync_semaphore.rs

@@ -1,21 +1,36 @@
-use bencher::Bencher;
 use std::sync::Arc;
+use tokio::runtime::Runtime;
 use tokio::{sync::Semaphore, task};
 
-fn uncontended(b: &mut Bencher) {
-    let rt = tokio::runtime::Builder::new_multi_thread()
+use criterion::measurement::WallTime;
+use criterion::{criterion_group, criterion_main, BenchmarkGroup, Criterion};
+
+fn single_rt() -> Runtime {
+    tokio::runtime::Builder::new_current_thread()
+        .build()
+        .unwrap()
+}
+
+fn multi_rt() -> Runtime {
+    tokio::runtime::Builder::new_multi_thread()
         .worker_threads(6)
         .build()
-        .unwrap();
+        .unwrap()
+}
+
+fn uncontended(g: &mut BenchmarkGroup<WallTime>) {
+    let rt = multi_rt();
 
     let s = Arc::new(Semaphore::new(10));
-    b.iter(|| {
-        let s = s.clone();
-        rt.block_on(async move {
-            for _ in 0..6 {
-                let permit = s.acquire().await;
-                drop(permit);
-            }
+    g.bench_function("multi", |b| {
+        b.iter(|| {
+            let s = s.clone();
+            rt.block_on(async move {
+                for _ in 0..6 {
+                    let permit = s.acquire().await;
+                    drop(permit);
+                }
+            })
         })
     });
 }
@@ -25,101 +40,108 @@ async fn task(s: Arc<Semaphore>) {
     drop(permit);
 }
 
-fn uncontended_concurrent_multi(b: &mut Bencher) {
-    let rt = tokio::runtime::Builder::new_multi_thread()
-        .worker_threads(6)
-        .build()
-        .unwrap();
+fn uncontended_concurrent_multi(g: &mut BenchmarkGroup<WallTime>) {
+    let rt = multi_rt();
 
     let s = Arc::new(Semaphore::new(10));
-    b.iter(|| {
-        let s = s.clone();
-        rt.block_on(async move {
-            let j = tokio::try_join! {
-                task::spawn(task(s.clone())),
-                task::spawn(task(s.clone())),
-                task::spawn(task(s.clone())),
-                task::spawn(task(s.clone())),
-                task::spawn(task(s.clone())),
-                task::spawn(task(s.clone()))
-            };
-            j.unwrap();
+    g.bench_function("concurrent_multi", |b| {
+        b.iter(|| {
+            let s = s.clone();
+            rt.block_on(async move {
+                let j = tokio::try_join! {
+                    task::spawn(task(s.clone())),
+                    task::spawn(task(s.clone())),
+                    task::spawn(task(s.clone())),
+                    task::spawn(task(s.clone())),
+                    task::spawn(task(s.clone())),
+                    task::spawn(task(s.clone()))
+                };
+                j.unwrap();
+            })
         })
     });
 }
 
-fn uncontended_concurrent_single(b: &mut Bencher) {
-    let rt = tokio::runtime::Builder::new_current_thread()
-        .build()
-        .unwrap();
+fn uncontended_concurrent_single(g: &mut BenchmarkGroup<WallTime>) {
+    let rt = single_rt();
 
     let s = Arc::new(Semaphore::new(10));
-    b.iter(|| {
-        let s = s.clone();
-        rt.block_on(async move {
-            tokio::join! {
-                task(s.clone()),
-                task(s.clone()),
-                task(s.clone()),
-                task(s.clone()),
-                task(s.clone()),
-                task(s.clone())
-            };
+    g.bench_function("concurrent_single", |b| {
+        b.iter(|| {
+            let s = s.clone();
+            rt.block_on(async move {
+                tokio::join! {
+                    task(s.clone()),
+                    task(s.clone()),
+                    task(s.clone()),
+                    task(s.clone()),
+                    task(s.clone()),
+                    task(s.clone())
+                };
+            })
         })
     });
 }
 
-fn contended_concurrent_multi(b: &mut Bencher) {
-    let rt = tokio::runtime::Builder::new_multi_thread()
-        .worker_threads(6)
-        .build()
-        .unwrap();
+fn contended_concurrent_multi(g: &mut BenchmarkGroup<WallTime>) {
+    let rt = multi_rt();
 
     let s = Arc::new(Semaphore::new(5));
-    b.iter(|| {
-        let s = s.clone();
-        rt.block_on(async move {
-            let j = tokio::try_join! {
-                task::spawn(task(s.clone())),
-                task::spawn(task(s.clone())),
-                task::spawn(task(s.clone())),
-                task::spawn(task(s.clone())),
-                task::spawn(task(s.clone())),
-                task::spawn(task(s.clone()))
-            };
-            j.unwrap();
+    g.bench_function("concurrent_multi", |b| {
+        b.iter(|| {
+            let s = s.clone();
+            rt.block_on(async move {
+                let j = tokio::try_join! {
+                    task::spawn(task(s.clone())),
+                    task::spawn(task(s.clone())),
+                    task::spawn(task(s.clone())),
+                    task::spawn(task(s.clone())),
+                    task::spawn(task(s.clone())),
+                    task::spawn(task(s.clone()))
+                };
+                j.unwrap();
+            })
         })
     });
 }
 
-fn contended_concurrent_single(b: &mut Bencher) {
-    let rt = tokio::runtime::Builder::new_current_thread()
-        .build()
-        .unwrap();
+fn contended_concurrent_single(g: &mut BenchmarkGroup<WallTime>) {
+    let rt = single_rt();
 
     let s = Arc::new(Semaphore::new(5));
-    b.iter(|| {
-        let s = s.clone();
-        rt.block_on(async move {
-            tokio::join! {
-                task(s.clone()),
-                task(s.clone()),
-                task(s.clone()),
-                task(s.clone()),
-                task(s.clone()),
-                task(s.clone())
-            };
+    g.bench_function("concurrent_single", |b| {
+        b.iter(|| {
+            let s = s.clone();
+            rt.block_on(async move {
+                tokio::join! {
+                    task(s.clone()),
+                    task(s.clone()),
+                    task(s.clone()),
+                    task(s.clone()),
+                    task(s.clone()),
+                    task(s.clone())
+                };
+            })
         })
     });
 }
 
-bencher::benchmark_group!(
-    sync_semaphore,
-    uncontended,
-    uncontended_concurrent_multi,
-    uncontended_concurrent_single,
-    contended_concurrent_multi,
-    contended_concurrent_single
-);
+fn bench_contention(c: &mut Criterion) {
+    let mut group = c.benchmark_group("contention");
+    contended_concurrent_multi(&mut group);
+    contended_concurrent_single(&mut group);
+    group.finish();
+}
 
-bencher::benchmark_main!(sync_semaphore);
+fn bench_uncontented(c: &mut Criterion) {
+    let mut group = c.benchmark_group("uncontented");
+    uncontended(&mut group);
+    uncontended_concurrent_multi(&mut group);
+    uncontended_concurrent_single(&mut group);
+    group.finish();
+}
+
+criterion_group!(contention, bench_contention);
+criterion_group!(uncontented, bench_uncontented);
+
+criterion_main!(contention, uncontented);

benches/sync_watch.rs

@@ -0,0 +1,85 @@
+use rand::prelude::*;
+use std::sync::atomic::{AtomicU64, Ordering};
+use std::sync::Arc;
+use tokio::sync::{watch, Notify};
+
+use criterion::measurement::WallTime;
+use criterion::{black_box, criterion_group, criterion_main, BenchmarkGroup, Criterion};
+
+fn rt() -> tokio::runtime::Runtime {
+    tokio::runtime::Builder::new_multi_thread()
+        .worker_threads(6)
+        .build()
+        .unwrap()
+}
+
+fn do_work(rng: &mut impl RngCore) -> u32 {
+    use std::fmt::Write;
+    let mut message = String::new();
+    for i in 1..=10 {
+        let _ = write!(&mut message, " {i}={}", rng.gen::<f64>());
+    }
+    message
+        .as_bytes()
+        .iter()
+        .map(|&c| c as u32)
+        .fold(0, u32::wrapping_add)
+}
+
+fn contention_resubscribe<const N_TASKS: usize>(g: &mut BenchmarkGroup<WallTime>) {
+    let rt = rt();
+    let (snd, _) = watch::channel(0i32);
+    let snd = Arc::new(snd);
+    let wg = Arc::new((AtomicU64::new(0), Notify::new()));
+    for n in 0..N_TASKS {
+        let mut rcv = snd.subscribe();
+        let wg = wg.clone();
+        let mut rng = rand::rngs::StdRng::seed_from_u64(n as u64);
+        rt.spawn(async move {
+            while rcv.changed().await.is_ok() {
+                let _ = *rcv.borrow(); // contend on rwlock
+                let r = do_work(&mut rng);
+                let _ = black_box(r);
+                if wg.0.fetch_sub(1, Ordering::Release) == 1 {
+                    wg.1.notify_one();
+                }
+            }
+        });
+    }
+
+    const N_ITERS: usize = 100;
+    g.bench_function(N_TASKS.to_string(), |b| {
+        b.iter(|| {
+            rt.block_on({
+                let snd = snd.clone();
+                let wg = wg.clone();
+                async move {
+                    tokio::spawn(async move {
+                        for _ in 0..N_ITERS {
+                            assert_eq!(wg.0.fetch_add(N_TASKS as u64, Ordering::Relaxed), 0);
+                            let _ = snd.send(black_box(42));
+                            while wg.0.load(Ordering::Acquire) > 0 {
+                                wg.1.notified().await;
+                            }
+                        }
+                    })
+                    .await
+                    .unwrap();
+                }
+            });
+        })
+    });
+}
+
+fn bench_contention_resubscribe(c: &mut Criterion) {
+    let mut group = c.benchmark_group("contention_resubscribe");
+    contention_resubscribe::<10>(&mut group);
+    contention_resubscribe::<100>(&mut group);
+    contention_resubscribe::<500>(&mut group);
+    contention_resubscribe::<1000>(&mut group);
+    group.finish();
+}
+
+criterion_group!(contention, bench_contention_resubscribe);
+
+criterion_main!(contention);

benches/time_now.rs

@@ -0,0 +1,24 @@
+//! Benchmark spawning a task onto the basic and threaded Tokio executors.
+//! This essentially measure the time to enqueue a task in the local and remote
+//! case.
+
+use criterion::{black_box, criterion_group, criterion_main, Criterion};
+
+fn time_now_current_thread(c: &mut Criterion) {
+    let rt = tokio::runtime::Builder::new_current_thread()
+        .enable_time()
+        .build()
+        .unwrap();
+
+    c.bench_function("time_now_current_thread", |b| {
+        b.iter(|| {
+            rt.block_on(async {
+                black_box(tokio::time::Instant::now());
+            })
+        })
+    });
+}
+
+criterion_group!(time_now, time_now_current_thread);
+
+criterion_main!(time_now);

benches/time_timeout.rs

@@ -0,0 +1,109 @@
+use std::time::{Duration, Instant};
+
+use criterion::{black_box, criterion_group, criterion_main, Criterion};
+use tokio::{
+    runtime::Runtime,
+    time::{sleep, timeout},
+};
+
+// a very quick async task, but might timeout
+async fn quick_job() -> usize {
+    1
+}
+
+fn build_run_time(workers: usize) -> Runtime {
+    if workers == 1 {
+        tokio::runtime::Builder::new_current_thread()
+            .enable_all()
+            .build()
+            .unwrap()
+    } else {
+        tokio::runtime::Builder::new_multi_thread()
+            .enable_all()
+            .worker_threads(workers)
+            .build()
+            .unwrap()
+    }
+}
+
+fn single_thread_scheduler_timeout(c: &mut Criterion) {
+    do_timeout_test(c, 1, "single_thread_timeout");
+}
+
+fn multi_thread_scheduler_timeout(c: &mut Criterion) {
+    do_timeout_test(c, 8, "multi_thread_timeout-8");
+}
+
+fn do_timeout_test(c: &mut Criterion, workers: usize, name: &str) {
+    let runtime = build_run_time(workers);
+    c.bench_function(name, |b| {
+        b.iter_custom(|iters| {
+            let start = Instant::now();
+            runtime.block_on(async {
+                black_box(spawn_timeout_job(iters as usize, workers)).await;
+            });
+            start.elapsed()
+        })
+    });
+}
+
+async fn spawn_timeout_job(iters: usize, procs: usize) {
+    let mut handles = Vec::with_capacity(procs);
+    for _ in 0..procs {
+        handles.push(tokio::spawn(async move {
+            for _ in 0..iters / procs {
+                let h = timeout(Duration::from_secs(1), quick_job());
+                assert_eq!(black_box(h.await.unwrap()), 1);
+            }
+        }));
+    }
+    for handle in handles {
+        handle.await.unwrap();
+    }
+}
+
+fn single_thread_scheduler_sleep(c: &mut Criterion) {
+    do_sleep_test(c, 1, "single_thread_sleep");
+}
+
+fn multi_thread_scheduler_sleep(c: &mut Criterion) {
+    do_sleep_test(c, 8, "multi_thread_sleep-8");
+}
+
+fn do_sleep_test(c: &mut Criterion, workers: usize, name: &str) {
+    let runtime = build_run_time(workers);
+
+    c.bench_function(name, |b| {
+        b.iter_custom(|iters| {
+            let start = Instant::now();
+            runtime.block_on(async {
+                black_box(spawn_sleep_job(iters as usize, workers)).await;
+            });
+            start.elapsed()
+        })
+    });
+}
+
+async fn spawn_sleep_job(iters: usize, procs: usize) {
+    let mut handles = Vec::with_capacity(procs);
+    for _ in 0..procs {
+        handles.push(tokio::spawn(async move {
+            for _ in 0..iters / procs {
+                let _h = black_box(sleep(Duration::from_secs(1)));
+            }
+        }));
+    }
+    for handle in handles {
+        handle.await.unwrap();
+    }
+}
+
+criterion_group!(
+    timeout_benchmark,
+    single_thread_scheduler_timeout,
+    multi_thread_scheduler_timeout,
+    single_thread_scheduler_sleep,
+    multi_thread_scheduler_sleep
+);
+
+criterion_main!(timeout_benchmark);

bin/publish

@@ -1,121 +0,0 @@
-#!/usr/bin/env bash
-set -e
-USAGE="Publish a new release of a tokio crate
-
-USAGE:
-    $(basename "$0") [OPTIONS] [CRATE] [VERSION]
-
-OPTIONS:
-    -v, --verbose   Use verbose Cargo output
-    -d, --dry-run   Perform a dry run (do not publish or tag the release)
-    -h, --help      Show this help text and exit"
-
-DRY_RUN=""
-VERBOSE=""
-
-err() {
-    echo -e "\e[31m\e[1merror:\e[0m $@" 1>&2;
-}
-
-status() {
-    WIDTH=12
-    printf "\e[32m\e[1m%${WIDTH}s\e[0m %s\n" "$1" "$2"
-}
-
-verify() {
-    status "Verifying" "if $CRATE v$VERSION can be released"
-    ACTUAL=$(cargo pkgid | sed -n 's/.*#\(.*\)/\1/p')
-
-    if [ "$ACTUAL" != "$VERSION" ]; then
-        err "expected to release version $VERSION, but Cargo.toml contained $ACTUAL"
-        exit 1
-    fi
-
-    if git tag -l | grep -Fxq "$TAG" ; then
-        err "git tag \`$TAG\` already exists"
-        exit 1
-    fi
-
-    PATH_DEPS=$(grep -F "path = \"" Cargo.toml | sed -e 's/^/  /')
-    if [ -n "$PATH_DEPS" ]; then
-        err "crate \`$CRATE\` contained path dependencies:\n$PATH_DEPS"
-        echo "path dependencies must be removed prior to release"
-        exit 1
-    fi
-}
-
-release() {
-    status "Releasing" "$CRATE v$VERSION"
-    cargo package $VERBOSE
-    cargo publish $VERBOSE $DRY_RUN
-
-    status "Tagging" "$TAG"
-    if [ -n "$DRY_RUN" ]; then
-        echo "# git tag $TAG && git push --tags"
-    else
-        git tag "$TAG" && git push --tags
-    fi
-}
-
-while [[ $# -gt 0 ]]
-do
-
-case "$1" in
-    -h|--help)
-    echo "$USAGE"
-    exit 0
-    ;;
-    -v|--verbose)
-    VERBOSE="--verbose"
-    set +x
-    shift
-    ;;
-    -d|--dry-run)
-    DRY_RUN="--dry-run"
-    shift
-    ;;
-    -*)
-    err "unknown flag \"$1\""
-    echo "$USAGE"
-    exit 1
-    ;;
-    *) # crate or version
-    if [ -z "$CRATE" ]; then
-        CRATE="$1"
-    elif [ -z "$VERSION" ]; then
-        VERSION="$1"
-    else
-        err "unknown positional argument \"$1\""
-        echo "$USAGE"
-        exit 1
-    fi
-    shift
-    ;;
-esac
-done
-# set -- "${POSITIONAL[@]}"
-
-if [ -z "$VERSION" ]; then
-    err "no version specified!"
-    HELP=1
-fi
-
-if [ -n "$CRATE" ]; then
-    TAG="$CRATE-$VERSION"
-else
-    err "no crate specified!"
-    HELP=1
-fi
-
-if [ -n "$HELP" ]; then
-    echo "$USAGE"
-    exit 1
-fi
-
-if [ -d "$CRATE" ]; then
-    (cd "$CRATE" && verify && release )
-else
-    err "no such crate \"$CRATE\""
-    exit 1
-fi
-

bin/update-doc

@@ -1,118 +0,0 @@
-#!/usr/bin/env bash
-set -e
-USAGE="Update links to docs.rs in a tokio crate
-
-USAGE:
-    $(basename "$0") [OPTIONS] [CRATE] [VERSION]
-
-OPTIONS:
-    -d, --dry-run       Perform a dry run (do not modify any file)
-    -h, --help          Show this help text and exit"
-
-err() {
-    echo -e "\e[31m\e[1merror:\e[0m $@" 1>&2;
-}
-
-status() {
-    WIDTH=12
-    printf "\e[32m\e[1m%${WIDTH}s\e[0m %s\n" "$1" "$2"
-}
-
-c1grep() { grep "$@" || test $? = 1; }
-
-update_versions_in_doc() {
-    # Print what is being/would be done
-    if [ -n "$DRY_RUN" ]; then
-        local MSG="Would change:"
-    else
-        local MSG="Updating:"
-    fi
-    git grep -lr "docs.rs/$CRATE/" \
-        | xargs sed --quiet \
-            -E "s|docs.rs/$CRATE/[0-9.]+|docs.rs/$CRATE/$VERSION|gp" \
-        | sed -e "s/^/$MSG /"
-
-    # Apply changes if not in dry run
-    if [ -z "$DRY_RUN" ]; then
-        git grep -lr "docs.rs/$CRATE/" \
-            | xargs sed -i \
-                -E "s|docs.rs/$CRATE/[0-9.]+|docs.rs/$CRATE/$VERSION|g"
-    fi
-}
-
-update() {
-    update_versions_in_doc
-}
-
-show_outdated() {
-    OUTDATED=$(git grep -rn "docs.rs/$CRATE/" \
-        | c1grep -v "$VERSION" \
-        | sed -e 's/^/ - /')
-    if [[ -n "$OUTDATED" ]]; then
-        echo "Found the following links to docs.rs with an outdated version:"
-        echo "$OUTDATED"
-        echo
-    else
-        echo "Nothing to do."
-        exit 1
-    fi
-}
-
-while [[ $# -gt 0 ]]
-do
-
-case "$1" in
-    -h|--help)
-    echo "$USAGE"
-    exit 0
-    ;;
-    -d|--dry-run)
-    DRY_RUN="--dry-run"
-    shift
-    ;;
-    -*)
-    err "unknown flag \"$1\""
-    echo "$USAGE"
-    exit 1
-    ;;
-    *) # crate or version
-    if [ -z "$CRATE" ]; then
-        CRATE="$1"
-    elif [ -z "$VERSION" ]; then
-        VERSION="$1"
-    else
-        err "unknown positional argument \"$1\""
-        echo "$USAGE"
-        exit 1
-    fi
-    shift
-    ;;
-esac
-done
-# set -- "${POSITIONAL[@]}"
-
-if [ -z "$VERSION" ]; then
-    err "no version specified!"
-    HELP=1
-fi
-
-if [ -n "$CRATE" ]; then
-    TAG="$CRATE-$VERSION"
-else
-    err "no crate specified!"
-    HELP=1
-fi
-
-if [ -n "$HELP" ]; then
-    echo "$USAGE"
-    exit 1
-fi
-
-if [ -d "$CRATE" ]; then
-    # Does not cd in order to update everywhere
-    show_outdated && update
-else
-    err "no such crate \"$CRATE\""
-    exit 1
-fi
-

examples/Cargo.toml

@@ -2,7 +2,7 @@
 name = "examples"
 version = "0.0.0"
 publish = false
-edition = "2018"
+edition = "2021"
 
 # If you copy one of the examples into a new project, you should be using
 # [dependencies] instead, and delete the **path**.
@@ -25,7 +25,7 @@ once_cell = "1.5.2"
 rand = "0.8.3"
 
 [target.'cfg(windows)'.dev-dependencies.windows-sys]
-version = "0.42.0"
+version = "0.48"
 
 [[example]]
 name = "chat"
@@ -90,3 +90,7 @@ path = "named-pipe-ready.rs"
 [[example]]
 name = "named-pipe-multi-client"
 path = "named-pipe-multi-client.rs"
+
+[[example]]
+name = "dump"
+path = "dump.rs"

examples/custom-executor-tokio-context.rs

@@ -23,7 +23,7 @@ fn main() {
 
     // Without the `HandleExt.wrap()` there would be a panic because there is
     // no timer running, since it would be referencing runtime r1.
-    let _ = rt1.block_on(rt2.wrap(async move {
+    rt1.block_on(rt2.wrap(async move {
         let listener = TcpListener::bind("0.0.0.0:0").await.unwrap();
         println!("addr: {:?}", listener.local_addr());
         tx.send(()).unwrap();

examples/dump.rs

@@ -0,0 +1,91 @@
+//! This example demonstrates tokio's experimental task dumping functionality.
+//! This application deadlocks. Input CTRL+C to display traces of each task, or
+//! input CTRL+C twice within 1 second to quit.
+
+#[cfg(all(
+    tokio_unstable,
+    tokio_taskdump,
+    target_os = "linux",
+    any(target_arch = "aarch64", target_arch = "x86", target_arch = "x86_64")
+))]
+#[tokio::main]
+async fn main() -> Result<(), Box<dyn std::error::Error>> {
+    use std::sync::Arc;
+    use tokio::sync::Barrier;
+
+    #[inline(never)]
+    async fn a(barrier: Arc<Barrier>) {
+        b(barrier).await
+    }
+
+    #[inline(never)]
+    async fn b(barrier: Arc<Barrier>) {
+        c(barrier).await
+    }
+
+    #[inline(never)]
+    async fn c(barrier: Arc<Barrier>) {
+        barrier.wait().await;
+    }
+
+    // Prints a task dump upon receipt of CTRL+C, or returns if CTRL+C is
+    // inputted twice within a second.
+    async fn dump_or_quit() {
+        use tokio::time::{timeout, Duration, Instant};
+        let handle = tokio::runtime::Handle::current();
+        let mut last_signal: Option<Instant> = None;
+        // wait for CTRL+C
+        while let Ok(_) = tokio::signal::ctrl_c().await {
+            // exit if a CTRL+C is inputted twice within 1 second
+            if let Some(time_since_last_signal) = last_signal.map(|i| i.elapsed()) {
+                if time_since_last_signal < Duration::from_secs(1) {
+                    return;
+                }
+            }
+            last_signal = Some(Instant::now());
+
+            // capture a dump, and print each trace
+            println!("{:-<80}", "");
+            if let Ok(dump) = timeout(Duration::from_secs(2), handle.dump()).await {
+                for task in dump.tasks().iter() {
+                    let id = task.id();
+                    let trace = task.trace();
+                    println!("TASK {id}:");
+                    println!("{trace}\n");
+                }
+            } else {
+                println!("Task dumping timed out. Use a native debugger (like gdb) to debug the deadlock.");
+            }
+            println!("{:-<80}", "");
+            println!("Input CTRL+C twice within 1 second to exit.");
+        }
+    }
+
+    println!("This program has a deadlock.");
+    println!("Input CTRL+C to print a task dump.");
+    println!("Input CTRL+C twice within 1 second to exit.");
+
+    // oops! this barrier waits for one more task than will ever come.
+    let barrier = Arc::new(Barrier::new(3));
+
+    let task_1 = tokio::spawn(a(barrier.clone()));
+    let task_2 = tokio::spawn(a(barrier));
+
+    tokio::select!(
+        _ = dump_or_quit() => {},
+        _ = task_1 => {},
+        _ = task_2 => {},
+    );
+
+    Ok(())
+}
+
+#[cfg(not(all(
+    tokio_unstable,
+    tokio_taskdump,
+    target_os = "linux",
+    any(target_arch = "aarch64", target_arch = "x86", target_arch = "x86_64")
+)))]
+fn main() {
+    println!("task dumps are not available")
+}

examples/proxy.rs

@@ -22,8 +22,7 @@
 
 #![warn(rust_2018_idioms)]
 
-use tokio::io;
-use tokio::io::AsyncWriteExt;
+use tokio::io::copy_bidirectional;
 use tokio::net::{TcpListener, TcpStream};
 
 use futures::FutureExt;
@@ -44,36 +43,19 @@ async fn main() -> Result<(), Box<dyn Error>> {
 
     let listener = TcpListener::bind(listen_addr).await?;
 
-    while let Ok((inbound, _)) = listener.accept().await {
-        let transfer = transfer(inbound, server_addr.clone()).map(|r| {
-            if let Err(e) = r {
-                println!("Failed to transfer; error={}", e);
-            }
-        });
+    while let Ok((mut inbound, _)) = listener.accept().await {
+        let mut outbound = TcpStream::connect(server_addr.clone()).await?;
 
-        tokio::spawn(transfer);
+        tokio::spawn(async move {
+            copy_bidirectional(&mut inbound, &mut outbound)
+                .map(|r| {
+                    if let Err(e) = r {
+                        println!("Failed to transfer; error={}", e);
+                    }
+                })
+                .await
+        });
     }
 
     Ok(())
 }
-
-async fn transfer(mut inbound: TcpStream, proxy_addr: String) -> Result<(), Box<dyn Error>> {
-    let mut outbound = TcpStream::connect(proxy_addr).await?;
-
-    let (mut ri, mut wi) = inbound.split();
-    let (mut ro, mut wo) = outbound.split();
-
-    let client_to_server = async {
-        io::copy(&mut ri, &mut wo).await?;
-        wo.shutdown().await
-    };
-
-    let server_to_client = async {
-        io::copy(&mut ro, &mut wi).await?;
-        wi.shutdown().await
-    };
-
-    tokio::try_join!(client_to_server, server_to_client)?;
-
-    Ok(())
-}

examples/tinyhttp.rs

@@ -180,8 +180,11 @@ impl Decoder for Http {
                 headers[i] = Some((k, v));
             }
 
+            let method = http::Method::try_from(r.method.unwrap())
+                .map_err(|e| io::Error::new(io::ErrorKind::Other, e))?;
+
             (
-                toslice(r.method.unwrap().as_bytes()),
+                method,
                 toslice(r.path.unwrap().as_bytes()),
                 r.version.unwrap(),
                 amt,
@@ -195,7 +198,7 @@ impl Decoder for Http {
         }
         let data = src.split_to(amt).freeze();
         let mut ret = Request::builder();
-        ret = ret.method(&data[method.0..method.1]);
+        ret = ret.method(method);
         let s = data.slice(path.0..path.1);
         let s = unsafe { String::from_utf8_unchecked(Vec::from(s.as_ref())) };
         ret = ret.uri(s);
@@ -256,11 +259,11 @@ mod date {
         unix_date: u64,
     }
 
-    thread_local!(static LAST: RefCell<LastRenderedNow> = RefCell::new(LastRenderedNow {
+    thread_local!(static LAST: RefCell<LastRenderedNow> = const { RefCell::new(LastRenderedNow {
         bytes: [0; 128],
         amt: 0,
         unix_date: 0,
-    }));
+    }) });
 
     impl fmt::Display for Now {
         fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {

netlify.toml

@@ -8,8 +8,9 @@
   RUSTDOCFLAGS="""
     --cfg docsrs \
     --cfg tokio_unstable \
+    --cfg tokio_taskdump \
     """
-  RUSTFLAGS="--cfg tokio_unstable --cfg docsrs"
+  RUSTFLAGS="--cfg tokio_unstable --cfg tokio_taskdump --cfg docsrs"
 
 [[redirects]]
   from = "/"

spellcheck.dic

@@ -0,0 +1,285 @@
+285
+&
++
+<
+=
+>
+\
+~
+—
+0o777
+0s
+0xA
+0xD
+100ms
+10ms
+~12
+±1m
+±1ms
+1ms
+1s
+250ms
+2x
+~4
+443
+450ms
+50ms
+8MB
+adaptor
+adaptors
+Adaptors
+AIO
+ambiant
+amongst
+api
+APIs
+async
+atomics
+awaitable
+backend
+backpressure
+backtrace
+backtraces
+backtracing
+binded
+bitfield
+bitfields
+Blockingly
+boolean
+broadcasted
+cancelled
+cancelling
+Cancelling
+CLI
+cloneable
+codebase
+codec
+codecs
+combinator
+combinators
+config
+Config
+connectionless
+coroutines
+cpu
+cpus
+Customizable
+datagram
+Datagram
+datagrams
+deallocate
+deallocated
+Deallocates
+decrementing
+dequeued
+deregister
+deregistered
+deregistering
+deregisters
+Deregisters
+deregistration
+descriptor's
+destructor
+destructors
+destructure
+Destructures
+Dev
+dns
+DNS
+DoS
+dwOpenMode
+endian
+enqueue
+enqueued
+EntryInner
+enum
+eof
+Erlang's
+errored
+EWMA
+expirations
+fcntl
+fd's
+FIFOs
+filename
+filesystem
+filesystems
+fn
+fns
+FreeBSD
+frontend
+fs
+functionalities
+getters
+GID
+goroutines
+Growable
+gzip
+hashmaps
+HashMaps
+hashsets
+ie
+Illumos
+impl
+implementers
+implementor
+implementors
+incrementing
+interoperate
+invariants
+Invariants
+io
+IOCP
+iOS
+IOs
+io_uring
+IP
+IPv4
+IPv6
+iteratively
+Kotlin's
+latencies
+Lauck
+libc
+lifecycle
+lifo
+lookups
+macOS
+MacOS
+Marsaglia's
+metadata
+mio
+Mio
+mio's
+misconfigured
+mock's
+mpmc
+mpsc
+multi
+Multi
+multicast
+Multithreaded
+mut
+mutex
+Mutex
+Nagle
+nonblocking
+nondecreasing
+noop
+ntasks
+ok
+oneshot
+ORed
+os
+overweighing
+parker
+parsers
+peekable
+PGID
+PID
+plaintext
+poller
+POSIX
+proxied
+qos
+RAII
+reallocations
+recv's
+refactors
+refcount
+refcounting
+repo
+repr
+representable
+reqwest
+reregistering
+resize
+resized
+RMW
+runtime
+runtime's
+runtimes
+rwlock
+rx
+scalability
+scheduler's
+semver
+setpgid
+sharded
+signalled
+signalling
+SmallCrush
+Solaris
+spawner
+Splitter
+spmc
+spsc
+src
+stabilised
+startup
+stateful
+stderr
+stdin
+stdout
+stealable
+stealer
+stealers
+struct
+structs
+subfield
+suboptimal
+subprocess
+superset
+symlink
+symlinks
+sys
+syscall
+syscalls
+tcp
+TCP
+TestU01
+threadpool
+timestamp
+timestamps
+TLS
+TOCTOU
+TODO
+tokio
+Tokio
+tokio's
+Tokio's
+tuple
+Tuple
+tx
+udp
+UDP
+UID
+unhandled
+unix
+unlink
+unpark
+Unpark
+unparked
+unparking
+unparks
+Unparks
+unreceived
+unsafety
+Unsets
+unsynchronized
+untrusted
+usecases
+Valgrind
+Varghese
+vec
+versa
+versioned
+versioning
+vtable
+waker
+wakers
+Wakers
+wakeup
+wakeups
+workstealing
+

spellcheck.toml

@@ -0,0 +1,13 @@
+dev_comments = false
+skip_readme = false
+
+[Hunspell]
+lang = "en_US"
+search_dirs = ["."]
+extra_dictionaries = ["spellcheck.dic"]
+skip_os_lookups = true
+use_builtin = true
+
+[Hunspell.quirks]
+allow_concatenation = true
+

stress-test/Cargo.toml

@@ -2,7 +2,7 @@
 name = "stress-test"
 version = "0.1.0"
 authors = ["Tokio Contributors <[email protected]>"]
-edition = "2018"
+edition = "2021"
 publish = false
 
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html

stress-test/examples/simple_echo_tcp.rs

@@ -42,7 +42,7 @@ fn main() {
                 .write_all(one_mega_random_bytes.as_slice())
                 .await
                 .unwrap();
-            stream.read(&mut buff).await.unwrap();
+            let _ = stream.read(&mut buff).await.unwrap();
         }
         tx.send(()).unwrap();
     });

target-specs/README.md

@@ -0,0 +1,9 @@
+This is used for the `no-atomic-u64-test` ci check that verifies that Tokio
+works even if the `AtomicU64` type is missing.
+
+When increasing the nightly compiler version, you may need to regenerate this
+target using the following command:
+```
+rustc +nightly -Z unstable-options --print target-spec-json --target i686-unknown-linux-gnu | grep -v 'is-builtin' | sed 's/"max-atomic-width": 64/"max-atomic-width": 32/' > target-specs/i686-unknown-linux-gnu.json
+```
+

target-specs/i686-unknown-linux-gnu.json

@@ -1,29 +1,35 @@
 {
   "arch": "x86",
   "cpu": "pentium4",
+  "crt-objects-fallback": "false",
   "crt-static-respected": true,
-  "data-layout": "e-m:e-p:32:32-p270:32:32-p271:32:32-p272:64:64-f64:32:64-f80:32-n8:16:32-S128",
+  "data-layout": "e-m:e-p:32:32-p270:32:32-p271:32:32-p272:64:64-i128:128-f64:32:64-f80:32-n8:16:32-S128",
   "dynamic-linking": true,
   "env": "gnu",
   "has-rpath": true,
   "has-thread-local": true,
+  "linker-flavor": "gnu-cc",
   "llvm-target": "i686-unknown-linux-gnu",
   "max-atomic-width": 32,
+  "metadata": {
+    "description": null,
+    "host_tools": null,
+    "std": null,
+    "tier": null
+  },
   "os": "linux",
   "position-independent-executables": true,
   "pre-link-args": {
-    "gcc": [
+    "gnu-cc": [
+      "-m32"
+    ],
+    "gnu-lld-cc": [
       "-m32"
     ]
   },
   "relro-level": "full",
   "stack-probes": {
-    "kind": "inline-or-call",
-    "min-llvm-version-for-inline": [
-      16,
-      0,
-      0
-    ]
+    "kind": "inline"
   },
   "supported-sanitizers": [
     "address"

tests-build/Cargo.toml

@@ -2,7 +2,7 @@
 name = "tests-build"
 version = "0.1.0"
 authors = ["Tokio Contributors <[email protected]>"]
-edition = "2018"
+edition = "2021"
 publish = false
 
 [features]

tests-build/tests/fail/macros_invalid_input.rs

@@ -36,16 +36,33 @@ async fn test_worker_threads_not_int() {}
 async fn test_worker_threads_and_current_thread() {}
 
 #[tokio::test(crate = 456)]
-async fn test_crate_not_ident_int() {}
+async fn test_crate_not_path_int() {}
 
 #[tokio::test(crate = "456")]
-async fn test_crate_not_ident_invalid() {}
-
-#[tokio::test(crate = "abc::edf")]
-async fn test_crate_not_ident_path() {}
+async fn test_crate_not_path_invalid() {}
 
 #[tokio::test]
 #[test]
 async fn test_has_second_test_attr() {}
 
+#[tokio::test]
+#[::core::prelude::v1::test]
+async fn test_has_second_test_attr_v1() {}
+
+#[tokio::test]
+#[core::prelude::rust_2015::test]
+async fn test_has_second_test_attr_rust_2015() {}
+
+#[tokio::test]
+#[::std::prelude::rust_2018::test]
+async fn test_has_second_test_attr_rust_2018() {}
+
+#[tokio::test]
+#[std::prelude::rust_2021::test]
+async fn test_has_second_test_attr_rust_2021() {}
+
+#[tokio::test]
+#[tokio::test]
+async fn test_has_generated_second_test_attr() {}
+
 fn main() {}

tests-build/tests/fail/macros_invalid_input.stderr

@@ -64,38 +64,52 @@ error: The `worker_threads` option requires the `multi_thread` runtime flavor. U
 35 | #[tokio::test(flavor = "current_thread", worker_threads = 4)]
    |                                                           ^
 
-error: Failed to parse value of `crate` as ident.
+error: Failed to parse value of `crate` as path.
   --> $DIR/macros_invalid_input.rs:38:23
    |
 38 | #[tokio::test(crate = 456)]
    |                       ^^^
 
-error: Failed to parse value of `crate` as ident: "456"
+error: Failed to parse value of `crate` as path: "456"
   --> $DIR/macros_invalid_input.rs:41:23
    |
 41 | #[tokio::test(crate = "456")]
    |                       ^^^^^
 
-error: Failed to parse value of `crate` as ident: "abc::edf"
-  --> $DIR/macros_invalid_input.rs:44:23
+error: second test attribute is supplied, consider removing or changing the order of your test attributes
+  --> $DIR/macros_invalid_input.rs:45:1
    |
-44 | #[tokio::test(crate = "abc::edf")]
-   |                       ^^^^^^^^^^
-
-error: second test attribute is supplied
-  --> $DIR/macros_invalid_input.rs:48:1
-   |
-48 | #[test]
+45 | #[test]
    | ^^^^^^^
 
-error: duplicated attribute
-  --> $DIR/macros_invalid_input.rs:48:1
+error: second test attribute is supplied, consider removing or changing the order of your test attributes
+  --> $DIR/macros_invalid_input.rs:49:1
    |
-48 | #[test]
-   | ^^^^^^^
+49 | #[::core::prelude::v1::test]
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: second test attribute is supplied, consider removing or changing the order of your test attributes
+  --> $DIR/macros_invalid_input.rs:53:1
    |
-note: the lint level is defined here
-  --> $DIR/macros_invalid_input.rs:1:9
+53 | #[core::prelude::rust_2015::test]
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: second test attribute is supplied, consider removing or changing the order of your test attributes
+  --> $DIR/macros_invalid_input.rs:57:1
    |
-1  | #![deny(duplicate_macro_attributes)]
-   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^
+57 | #[::std::prelude::rust_2018::test]
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: second test attribute is supplied, consider removing or changing the order of your test attributes
+  --> $DIR/macros_invalid_input.rs:61:1
+   |
+61 | #[std::prelude::rust_2021::test]
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: second test attribute is supplied, consider removing or changing the order of your test attributes
+  --> $DIR/macros_invalid_input.rs:64:1
+   |
+64 | #[tokio::test]
+   | ^^^^^^^^^^^^^^
+   |
+   = note: this error originates in the attribute macro `tokio::test` (in Nightly builds, run with -Z macro-backtrace for more info)

tests-build/tests/fail/macros_type_mismatch.stderr

@@ -1,33 +1,45 @@
 error[E0308]: mismatched types
- --> $DIR/macros_type_mismatch.rs:5:5
+ --> tests/fail/macros_type_mismatch.rs:5:5
   |
-4 | async fn missing_semicolon_or_return_type() {
-  |                                             - help: a return type might be missing here: `-> _`
 5 |     Ok(())
-  |     ^^^^^^ expected `()`, found enum `Result`
+  |     ^^^^^^ expected `()`, found `Result<(), _>`
   |
   = note: expected unit type `()`
                   found enum `Result<(), _>`
+help: a return type might be missing here
+  |
+4 | async fn missing_semicolon_or_return_type() -> _ {
+  |                                             ++++
+help: consider using `Result::expect` to unwrap the `Result<(), _>` value, panicking if the value is a `Result::Err`
+  |
+5 |     Ok(()).expect("REASON")
+  |           +++++++++++++++++
 
 error[E0308]: mismatched types
-  --> $DIR/macros_type_mismatch.rs:10:5
+  --> tests/fail/macros_type_mismatch.rs:10:5
    |
-9  | async fn missing_return_type() {
-   |                                - help: a return type might be missing here: `-> _`
 10 |     return Ok(());
-   |     ^^^^^^^^^^^^^^ expected `()`, found enum `Result`
+   |     ^^^^^^^^^^^^^^ expected `()`, found `Result<(), _>`
    |
    = note: expected unit type `()`
                    found enum `Result<(), _>`
+help: a return type might be missing here
+   |
+9  | async fn missing_return_type() -> _ {
+   |                                ++++
+help: consider using `Result::expect` to unwrap the `Result<(), _>` value, panicking if the value is a `Result::Err`
+   |
+10 |     return Ok(());.expect("REASON")
+   |                   +++++++++++++++++
 
 error[E0308]: mismatched types
-  --> $DIR/macros_type_mismatch.rs:23:5
+  --> tests/fail/macros_type_mismatch.rs:23:5
    |
 14 | async fn extra_semicolon() -> Result<(), ()> {
    |                               -------------- expected `Result<(), ()>` because of return type
 ...
 23 |     Ok(());
-   |     ^^^^^^^ expected enum `Result`, found `()`
+   |     ^^^^^^^ expected `Result<(), ()>`, found `()`
    |
    = note:   expected enum `Result<(), ()>`
            found unit type `()`
@@ -38,10 +50,10 @@ help: try adding an expression at the end of the block
    |
 
 error[E0308]: mismatched types
-  --> $DIR/macros_type_mismatch.rs:32:5
+  --> tests/fail/macros_type_mismatch.rs:32:5
    |
 30 | async fn issue_4635() {
-   |                       - help: try adding a return type: `-> i32`
+   |                      - help: try adding a return type: `-> i32`
 31 |     return 1;
 32 |     ;
    |     ^ expected `()`, found integer

tests-integration/Cargo.toml

@@ -2,7 +2,7 @@
 name = "tests-integration"
 version = "0.1.0"
 authors = ["Tokio Contributors <[email protected]>"]
-edition = "2018"
+edition = "2021"
 publish = false
 
 [[bin]]
@@ -39,6 +39,7 @@ rt-process-signal = ["rt-net", "tokio/process", "tokio/signal"]
 # This is an explicit feature so we can use `cargo hack` testing single features
 # instead of all possible permutations.
 wasi-rt = ["rt", "macros", "sync"]
+wasi-threads-rt = ["wasi-rt", "rt-multi-thread"]
 
 full = [
     "macros",

tests-integration/tests/macros_main.rs

@@ -1,8 +1,4 @@
-#![cfg(all(
-    feature = "macros",
-    feature = "rt-multi-thread",
-    not(target_os = "wasi")
-))]
+#![cfg(all(feature = "macros", feature = "rt-multi-thread"))]
 
 #[tokio::main]
 async fn basic_main() -> usize {

tests-integration/tests/macros_select.rs

@@ -4,7 +4,10 @@ use futures::channel::oneshot;
 use futures::executor::block_on;
 use std::thread;
 
-#[cfg_attr(target_os = "wasi", ignore = "WASI: std::thread::spawn not supported")]
+#[cfg_attr(
+    not(feature = "rt-multi-thread"),
+    ignore = "WASI: std::thread::spawn not supported"
+)]
 #[test]
 fn join_with_select() {
     block_on(async {

tests-integration/tests/process_stdio.rs

@@ -7,7 +7,6 @@ use tokio::process::{Child, Command};
 use tokio_test::assert_ok;
 
 use futures::future::{self, FutureExt};
-use std::convert::TryInto;
 use std::env;
 use std::io;
 use std::process::{ExitStatus, Stdio};

tokio-macros/CHANGELOG.md

@@ -1,3 +1,40 @@
+# 2.3.0 (May 30th, 2024)
+
+- macros: make `#[tokio::test]` append `#[test]` at the end of the attribute list ([#6497])
+
+[#6497]: https://github.com/tokio-rs/tokio/pull/6497
+
+# 2.2.0 (November 19th, 2023)
+
+### Changed
+
+- use `::core` qualified imports instead of `::std` inside `tokio::test` macro ([#5973])
+
+[#5973]: https://github.com/tokio-rs/tokio/pull/5973
+
+# 2.1.0 (April 25th, 2023)
+
+- macros: fix typo in `#[tokio::test]` docs ([#5636])
+- macros: make entrypoints more efficient ([#5621])
+
+[#5621]: https://github.com/tokio-rs/tokio/pull/5621
+[#5636]: https://github.com/tokio-rs/tokio/pull/5636
+
+# 2.0.0 (March 24th, 2023)
+
+This major release updates the dependency on the syn crate to 2.0.0, and
+increases the MSRV to 1.56.
+
+As part of this release, we are adopting a policy of depending on a specific minor
+release of tokio-macros. This prevents Tokio from being able to pull in many different
+versions of tokio-macros.
+
+- macros: update `syn` ([#5572])
+- macros: accept path as crate rename ([#5557])
+
+[#5572]: https://github.com/tokio-rs/tokio/pull/5572
+[#5557]: https://github.com/tokio-rs/tokio/pull/5557
+
 # 1.8.2 (November 30th, 2022)
 
 - fix a regression introduced in 1.8.1 ([#5244])

tokio-macros/Cargo.toml

@@ -4,9 +4,9 @@ name = "tokio-macros"
 # - Remove path dependencies
 # - Update CHANGELOG.md.
 # - Create "tokio-macros-1.x.y" git tag.
-version = "1.8.2"
-edition = "2018"
-rust-version = "1.49"
+version = "2.3.0"
+edition = "2021"
+rust-version = "1.63"
 authors = ["Tokio Contributors <[email protected]>"]
 license = "MIT"
 repository = "https://github.com/tokio-rs/tokio"
@@ -22,9 +22,9 @@ proc-macro = true
 [features]
 
 [dependencies]
-proc-macro2 = "1.0.7"
+proc-macro2 = "1.0.60"
 quote = "1"
-syn = { version = "1.0.56", features = ["full"] }
+syn = { version = "2.0", features = ["full"] }
 
 [dev-dependencies]
 tokio = { version = "1.0.0", path = "../tokio", features = ["full"] }

tokio-macros/LICENSE

@@ -1,32 +1,7 @@
-Copyright (c) 2022 Tokio Contributors
-
-Permission is hereby granted, free of charge, to any
-person obtaining a copy of this software and associated
-documentation files (the "Software"), to deal in the
-Software without restriction, including without
-limitation the rights to use, copy, modify, merge,
-publish, distribute, sublicense, and/or sell copies of
-the Software, and to permit persons to whom the Software
-is furnished to do so, subject to the following
-conditions:
-
-The above copyright notice and this permission notice
-shall be included in all copies or substantial portions
-of the Software.
-
-THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF
-ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED
-TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
-PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT
-SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
-CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
-OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR
-IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
-DEALINGS IN THE SOFTWARE.
-
-The MIT License (MIT)
+MIT License
 
 Copyright (c) 2019 Yoshua Wuyts
+Copyright (c) Tokio Contributors
 
 Permission is hereby granted, free of charge, to any person obtaining a copy
 of this software and associated documentation files (the "Software"), to deal

tokio-macros/src/entry.rs

@@ -1,10 +1,10 @@
-use proc_macro::TokenStream;
-use proc_macro2::{Ident, Span};
+use proc_macro2::{Span, TokenStream, TokenTree};
 use quote::{quote, quote_spanned, ToTokens};
-use syn::parse::Parser;
+use syn::parse::{Parse, ParseStream, Parser};
+use syn::{braced, Attribute, Ident, Path, Signature, Visibility};
 
 // syn::AttributeArgs does not implement syn::Parse
-type AttributeArgs = syn::punctuated::Punctuated<syn::NestedMeta, syn::Token![,]>;
+type AttributeArgs = syn::punctuated::Punctuated<syn::Meta, syn::Token![,]>;
 
 #[derive(Clone, Copy, PartialEq)]
 enum RuntimeFlavor {
@@ -29,7 +29,7 @@ struct FinalConfig {
     flavor: RuntimeFlavor,
     worker_threads: Option<usize>,
     start_paused: Option<bool>,
-    crate_name: Option<String>,
+    crate_name: Option<Path>,
 }
 
 /// Config used in case of the attribute not being able to build a valid config
@@ -47,7 +47,7 @@ struct Configuration {
     worker_threads: Option<(usize, Span)>,
     start_paused: Option<(bool, Span)>,
     is_test: bool,
-    crate_name: Option<String>,
+    crate_name: Option<Path>,
 }
 
 impl Configuration {
@@ -112,8 +112,8 @@ impl Configuration {
         if self.crate_name.is_some() {
             return Err(syn::Error::new(span, "`crate` set multiple times."));
         }
-        let name_ident = parse_ident(name, span, "crate")?;
-        self.crate_name = Some(name_ident.to_string());
+        let name_path = parse_path(name, span, "crate")?;
+        self.crate_name = Some(name_path);
         Ok(())
     }
 
@@ -126,22 +126,22 @@ impl Configuration {
     }
 
     fn build(&self) -> Result<FinalConfig, syn::Error> {
-        let flavor = self.flavor.unwrap_or(self.default_flavor);
-        use RuntimeFlavor::*;
+        use RuntimeFlavor as F;
 
+        let flavor = self.flavor.unwrap_or(self.default_flavor);
         let worker_threads = match (flavor, self.worker_threads) {
-            (CurrentThread, Some((_, worker_threads_span))) => {
+            (F::CurrentThread, Some((_, worker_threads_span))) => {
                 let msg = format!(
                     "The `worker_threads` option requires the `multi_thread` runtime flavor. Use `#[{}(flavor = \"multi_thread\")]`",
                     self.macro_name(),
                 );
                 return Err(syn::Error::new(worker_threads_span, msg));
             }
-            (CurrentThread, None) => None,
-            (Threaded, worker_threads) if self.rt_multi_thread_available => {
+            (F::CurrentThread, None) => None,
+            (F::Threaded, worker_threads) if self.rt_multi_thread_available => {
                 worker_threads.map(|(val, _span)| val)
             }
-            (Threaded, _) => {
+            (F::Threaded, _) => {
                 let msg = if self.flavor.is_none() {
                     "The default runtime flavor is `multi_thread`, but the `rt-multi-thread` feature is disabled."
                 } else {
@@ -152,14 +152,14 @@ impl Configuration {
         };
 
         let start_paused = match (flavor, self.start_paused) {
-            (Threaded, Some((_, start_paused_span))) => {
+            (F::Threaded, Some((_, start_paused_span))) => {
                 let msg = format!(
                     "The `start_paused` option requires the `current_thread` runtime flavor. Use `#[{}(flavor = \"current_thread\")]`",
                     self.macro_name(),
                 );
                 return Err(syn::Error::new(start_paused_span, msg));
             }
-            (CurrentThread, Some((start_paused, _))) => Some(start_paused),
+            (F::CurrentThread, Some((start_paused, _))) => Some(start_paused),
             (_, None) => None,
         };
 
@@ -199,23 +199,22 @@ fn parse_string(int: syn::Lit, span: Span, field: &str) -> Result<String, syn::E
     }
 }
 
-fn parse_ident(lit: syn::Lit, span: Span, field: &str) -> Result<Ident, syn::Error> {
+fn parse_path(lit: syn::Lit, span: Span, field: &str) -> Result<Path, syn::Error> {
     match lit {
         syn::Lit::Str(s) => {
             let err = syn::Error::new(
                 span,
                 format!(
-                    "Failed to parse value of `{}` as ident: \"{}\"",
+                    "Failed to parse value of `{}` as path: \"{}\"",
                     field,
                     s.value()
                 ),
             );
-            let path = s.parse::<syn::Path>().map_err(|_| err.clone())?;
-            path.get_ident().cloned().ok_or(err)
+            s.parse::<syn::Path>().map_err(|_| err.clone())
         }
         _ => Err(syn::Error::new(
             span,
-            format!("Failed to parse value of `{}` as ident.", field),
+            format!("Failed to parse value of `{}` as path.", field),
         )),
     }
 }
@@ -231,7 +230,7 @@ fn parse_bool(bool: syn::Lit, span: Span, field: &str) -> Result<bool, syn::Erro
 }
 
 fn build_config(
-    input: syn::ItemFn,
+    input: &ItemFn,
     args: AttributeArgs,
     is_test: bool,
     rt_multi_thread: bool,
@@ -246,7 +245,7 @@ fn build_config(
 
     for arg in args {
         match arg {
-            syn::NestedMeta::Meta(syn::Meta::NameValue(namevalue)) => {
+            syn::Meta::NameValue(namevalue) => {
                 let ident = namevalue
                     .path
                     .get_ident()
@@ -255,34 +254,26 @@ fn build_config(
                     })?
                     .to_string()
                     .to_lowercase();
+                let lit = match &namevalue.value {
+                    syn::Expr::Lit(syn::ExprLit { lit, .. }) => lit,
+                    expr => return Err(syn::Error::new_spanned(expr, "Must be a literal")),
+                };
                 match ident.as_str() {
                     "worker_threads" => {
-                        config.set_worker_threads(
-                            namevalue.lit.clone(),
-                            syn::spanned::Spanned::span(&namevalue.lit),
-                        )?;
+                        config.set_worker_threads(lit.clone(), syn::spanned::Spanned::span(lit))?;
                     }
                     "flavor" => {
-                        config.set_flavor(
-                            namevalue.lit.clone(),
-                            syn::spanned::Spanned::span(&namevalue.lit),
-                        )?;
+                        config.set_flavor(lit.clone(), syn::spanned::Spanned::span(lit))?;
                     }
                     "start_paused" => {
-                        config.set_start_paused(
-                            namevalue.lit.clone(),
-                            syn::spanned::Spanned::span(&namevalue.lit),
-                        )?;
+                        config.set_start_paused(lit.clone(), syn::spanned::Spanned::span(lit))?;
                     }
                     "core_threads" => {
                         let msg = "Attribute `core_threads` is renamed to `worker_threads`";
                         return Err(syn::Error::new_spanned(namevalue, msg));
                     }
                     "crate" => {
-                        config.set_crate_name(
-                            namevalue.lit.clone(),
-                            syn::spanned::Spanned::span(&namevalue.lit),
-                        )?;
+                        config.set_crate_name(lit.clone(), syn::spanned::Spanned::span(lit))?;
                     }
                     name => {
                         let msg = format!(
@@ -293,7 +284,7 @@ fn build_config(
                     }
                 }
             }
-            syn::NestedMeta::Meta(syn::Meta::Path(path)) => {
+            syn::Meta::Path(path) => {
                 let name = path
                     .get_ident()
                     .ok_or_else(|| syn::Error::new_spanned(&path, "Must have specified ident"))?
@@ -333,18 +324,13 @@ fn build_config(
     config.build()
 }
 
-fn parse_knobs(mut input: syn::ItemFn, is_test: bool, config: FinalConfig) -> TokenStream {
+fn parse_knobs(mut input: ItemFn, is_test: bool, config: FinalConfig) -> TokenStream {
     input.sig.asyncness = None;
 
     // If type mismatch occurs, the current rustc points to the last statement.
     let (last_stmt_start_span, last_stmt_end_span) = {
-        let mut last_stmt = input
-            .block
-            .stmts
-            .last()
-            .map(ToTokens::into_token_stream)
-            .unwrap_or_default()
-            .into_iter();
+        let mut last_stmt = input.stmts.last().cloned().unwrap_or_default().into_iter();
+
         // `Span` on stable Rust has a limitation that only points to the first
         // token, not the whole tokens. We can work around this limitation by
         // using the first/last span of the tokens like
@@ -354,26 +340,27 @@ fn parse_knobs(mut input: syn::ItemFn, is_test: bool, config: FinalConfig) -> To
         (start, end)
     };
 
-    let crate_name = config.crate_name.as_deref().unwrap_or("tokio");
-
-    let crate_ident = Ident::new(crate_name, last_stmt_start_span);
+    let crate_path = config
+        .crate_name
+        .map(ToTokens::into_token_stream)
+        .unwrap_or_else(|| Ident::new("tokio", last_stmt_start_span).into_token_stream());
 
     let mut rt = match config.flavor {
         RuntimeFlavor::CurrentThread => quote_spanned! {last_stmt_start_span=>
-            #crate_ident::runtime::Builder::new_current_thread()
+            #crate_path::runtime::Builder::new_current_thread()
         },
         RuntimeFlavor::Threaded => quote_spanned! {last_stmt_start_span=>
-            #crate_ident::runtime::Builder::new_multi_thread()
+            #crate_path::runtime::Builder::new_multi_thread()
         },
     };
     if let Some(v) = config.worker_threads {
-        rt = quote! { #rt.worker_threads(#v) };
+        rt = quote_spanned! {last_stmt_start_span=> #rt.worker_threads(#v) };
     }
     if let Some(v) = config.start_paused {
-        rt = quote! { #rt.start_paused(#v) };
+        rt = quote_spanned! {last_stmt_start_span=> #rt.start_paused(#v) };
     }
 
-    let header = if is_test {
+    let generated_attrs = if is_test {
         quote! {
             #[::core::prelude::v1::test]
         }
@@ -381,10 +368,8 @@ fn parse_knobs(mut input: syn::ItemFn, is_test: bool, config: FinalConfig) -> To
         quote! {}
     };
 
-    let body = &input.block;
-    let brace_token = input.block.brace_token;
     let body_ident = quote! { body };
-    let block_expr = quote_spanned! {last_stmt_end_span=>
+    let last_block = quote_spanned! {last_stmt_end_span=>
         #[allow(clippy::expect_used, clippy::diverging_sub_expression)]
         {
             return #rt
@@ -395,6 +380,8 @@ fn parse_knobs(mut input: syn::ItemFn, is_test: bool, config: FinalConfig) -> To
         }
     };
 
+    let body = input.body();
+
     // For test functions pin the body to the stack and use `Pin<&mut dyn
     // Future>` to reduce the amount of `Runtime::block_on` (and related
     // functions) copies we generate during compilation due to the generic
@@ -414,8 +401,8 @@ fn parse_knobs(mut input: syn::ItemFn, is_test: bool, config: FinalConfig) -> To
         };
         quote! {
             let body = async #body;
-            #crate_ident::pin!(body);
-            let body: ::std::pin::Pin<&mut dyn ::std::future::Future<Output = #output_type>> = body;
+            #crate_path::pin!(body);
+            let body: ::core::pin::Pin<&mut dyn ::core::future::Future<Output = #output_type>> = body;
         }
     } else {
         quote! {
@@ -423,34 +410,19 @@ fn parse_knobs(mut input: syn::ItemFn, is_test: bool, config: FinalConfig) -> To
         }
     };
 
-    input.block = syn::parse2(quote! {
-        {
-            #body
-            #block_expr
-        }
-    })
-    .expect("Parsing failure");
-    input.block.brace_token = brace_token;
-
-    let result = quote! {
-        #header
-        #input
-    };
-
-    result.into()
+    input.into_tokens(generated_attrs, body, last_block)
 }
 
 fn token_stream_with_error(mut tokens: TokenStream, error: syn::Error) -> TokenStream {
-    tokens.extend(TokenStream::from(error.into_compile_error()));
+    tokens.extend(error.into_compile_error());
     tokens
 }
 
-#[cfg(not(test))] // Work around for rust-lang/rust#62127
 pub(crate) fn main(args: TokenStream, item: TokenStream, rt_multi_thread: bool) -> TokenStream {
     // If any of the steps for this macro fail, we still want to expand to an item that is as close
     // to the expected output as possible. This helps out IDEs such that completions and other
     // related features keep working.
-    let input: syn::ItemFn = match syn::parse(item.clone()) {
+    let input: ItemFn = match syn::parse2(item.clone()) {
         Ok(it) => it,
         Err(e) => return token_stream_with_error(item, e),
     };
@@ -460,8 +432,8 @@ pub(crate) fn main(args: TokenStream, item: TokenStream, rt_multi_thread: bool)
         Err(syn::Error::new_spanned(&input.sig.ident, msg))
     } else {
         AttributeArgs::parse_terminated
-            .parse(args)
-            .and_then(|args| build_config(input.clone(), args, false, rt_multi_thread))
+            .parse2(args)
+            .and_then(|args| build_config(&input, args, false, rt_multi_thread))
     };
 
     match config {
@@ -470,21 +442,50 @@ pub(crate) fn main(args: TokenStream, item: TokenStream, rt_multi_thread: bool)
     }
 }
 
+// Check whether given attribute is a test attribute of forms:
+// * `#[test]`
+// * `#[core::prelude::*::test]` or `#[::core::prelude::*::test]`
+// * `#[std::prelude::*::test]` or `#[::std::prelude::*::test]`
+fn is_test_attribute(attr: &Attribute) -> bool {
+    let path = match &attr.meta {
+        syn::Meta::Path(path) => path,
+        _ => return false,
+    };
+    let candidates = [
+        ["core", "prelude", "*", "test"],
+        ["std", "prelude", "*", "test"],
+    ];
+    if path.leading_colon.is_none()
+        && path.segments.len() == 1
+        && path.segments[0].arguments.is_none()
+        && path.segments[0].ident == "test"
+    {
+        return true;
+    } else if path.segments.len() != candidates[0].len() {
+        return false;
+    }
+    candidates.into_iter().any(|segments| {
+        path.segments.iter().zip(segments).all(|(segment, path)| {
+            segment.arguments.is_none() && (path == "*" || segment.ident == path)
+        })
+    })
+}
+
 pub(crate) fn test(args: TokenStream, item: TokenStream, rt_multi_thread: bool) -> TokenStream {
     // If any of the steps for this macro fail, we still want to expand to an item that is as close
     // to the expected output as possible. This helps out IDEs such that completions and other
     // related features keep working.
-    let input: syn::ItemFn = match syn::parse(item.clone()) {
+    let input: ItemFn = match syn::parse2(item.clone()) {
         Ok(it) => it,
         Err(e) => return token_stream_with_error(item, e),
     };
-    let config = if let Some(attr) = input.attrs.iter().find(|attr| attr.path.is_ident("test")) {
-        let msg = "second test attribute is supplied";
+    let config = if let Some(attr) = input.attrs().find(|attr| is_test_attribute(attr)) {
+        let msg = "second test attribute is supplied, consider removing or changing the order of your test attributes";
         Err(syn::Error::new_spanned(attr, msg))
     } else {
         AttributeArgs::parse_terminated
-            .parse(args)
-            .and_then(|args| build_config(input.clone(), args, true, rt_multi_thread))
+            .parse2(args)
+            .and_then(|args| build_config(&input, args, true, rt_multi_thread))
     };
 
     match config {
@@ -492,3 +493,128 @@ pub(crate) fn test(args: TokenStream, item: TokenStream, rt_multi_thread: bool)
         Err(e) => token_stream_with_error(parse_knobs(input, true, DEFAULT_ERROR_CONFIG), e),
     }
 }
+
+struct ItemFn {
+    outer_attrs: Vec<Attribute>,
+    vis: Visibility,
+    sig: Signature,
+    brace_token: syn::token::Brace,
+    inner_attrs: Vec<Attribute>,
+    stmts: Vec<proc_macro2::TokenStream>,
+}
+
+impl ItemFn {
+    /// Access all attributes of the function item.
+    fn attrs(&self) -> impl Iterator<Item = &Attribute> {
+        self.outer_attrs.iter().chain(self.inner_attrs.iter())
+    }
+
+    /// Get the body of the function item in a manner so that it can be
+    /// conveniently used with the `quote!` macro.
+    fn body(&self) -> Body<'_> {
+        Body {
+            brace_token: self.brace_token,
+            stmts: &self.stmts,
+        }
+    }
+
+    /// Convert our local function item into a token stream.
+    fn into_tokens(
+        self,
+        generated_attrs: proc_macro2::TokenStream,
+        body: proc_macro2::TokenStream,
+        last_block: proc_macro2::TokenStream,
+    ) -> TokenStream {
+        let mut tokens = proc_macro2::TokenStream::new();
+        // Outer attributes are simply streamed as-is.
+        for attr in self.outer_attrs {
+            attr.to_tokens(&mut tokens);
+        }
+
+        // Inner attributes require extra care, since they're not supported on
+        // blocks (which is what we're expanded into) we instead lift them
+        // outside of the function. This matches the behavior of `syn`.
+        for mut attr in self.inner_attrs {
+            attr.style = syn::AttrStyle::Outer;
+            attr.to_tokens(&mut tokens);
+        }
+
+        // Add generated macros at the end, so macros processed later are aware of them.
+        generated_attrs.to_tokens(&mut tokens);
+
+        self.vis.to_tokens(&mut tokens);
+        self.sig.to_tokens(&mut tokens);
+
+        self.brace_token.surround(&mut tokens, |tokens| {
+            body.to_tokens(tokens);
+            last_block.to_tokens(tokens);
+        });
+
+        tokens
+    }
+}
+
+impl Parse for ItemFn {
+    #[inline]
+    fn parse(input: ParseStream<'_>) -> syn::Result<Self> {
+        // This parse implementation has been largely lifted from `syn`, with
+        // the exception of:
+        // * We don't have access to the plumbing necessary to parse inner
+        //   attributes in-place.
+        // * We do our own statements parsing to avoid recursively parsing
+        //   entire statements and only look for the parts we're interested in.
+
+        let outer_attrs = input.call(Attribute::parse_outer)?;
+        let vis: Visibility = input.parse()?;
+        let sig: Signature = input.parse()?;
+
+        let content;
+        let brace_token = braced!(content in input);
+        let inner_attrs = Attribute::parse_inner(&content)?;
+
+        let mut buf = proc_macro2::TokenStream::new();
+        let mut stmts = Vec::new();
+
+        while !content.is_empty() {
+            if let Some(semi) = content.parse::<Option<syn::Token![;]>>()? {
+                semi.to_tokens(&mut buf);
+                stmts.push(buf);
+                buf = proc_macro2::TokenStream::new();
+                continue;
+            }
+
+            // Parse a single token tree and extend our current buffer with it.
+            // This avoids parsing the entire content of the sub-tree.
+            buf.extend([content.parse::<TokenTree>()?]);
+        }
+
+        if !buf.is_empty() {
+            stmts.push(buf);
+        }
+
+        Ok(Self {
+            outer_attrs,
+            vis,
+            sig,
+            brace_token,
+            inner_attrs,
+            stmts,
+        })
+    }
+}
+
+struct Body<'a> {
+    brace_token: syn::token::Brace,
+    // Statements, with terminating `;`.
+    stmts: &'a [TokenStream],
+}
+
+impl ToTokens for Body<'_> {
+    fn to_tokens(&self, tokens: &mut proc_macro2::TokenStream) {
+        self.brace_token.surround(tokens, |tokens| {
+            for stmt in self.stmts {
+                stmt.to_tokens(tokens);
+            }
+        });
+    }
+}

tokio-macros/src/lib.rs

@@ -1,3 +1,4 @@
+#![allow(unknown_lints, unexpected_cfgs)]
 #![allow(clippy::needless_doctest_main)]
 #![warn(
     missing_debug_implementations,
@@ -39,6 +40,13 @@ use proc_macro::TokenStream;
 /// function is called often, it is preferable to create the runtime using the
 /// runtime builder so the runtime can be reused across calls.
 ///
+/// # Non-worker async function
+///
+/// Note that the async function marked with this macro does not run as a
+/// worker. The expectation is that other tasks are spawned by the function here.
+/// Awaiting on other futures from the function provided here will not
+/// perform as fast as those spawned as workers.
+///
 /// # Multi-threaded runtime
 ///
 /// To use the multi-threaded runtime, the macro can be configured using
@@ -195,14 +203,13 @@ use proc_macro::TokenStream;
 /// }
 /// ```
 #[proc_macro_attribute]
-#[cfg(not(test))] // Work around for rust-lang/rust#62127
 pub fn main(args: TokenStream, item: TokenStream) -> TokenStream {
-    entry::main(args, item, true)
+    entry::main(args.into(), item.into(), true).into()
 }
 
 /// Marks async function to be executed by selected runtime. This macro helps set up a `Runtime`
 /// without requiring the user to use [Runtime](../tokio/runtime/struct.Runtime.html) or
-/// [Builder](../tokio/runtime/struct.builder.html) directly.
+/// [Builder](../tokio/runtime/struct.Builder.html) directly.
 ///
 /// ## Function arguments:
 ///
@@ -260,9 +267,8 @@ pub fn main(args: TokenStream, item: TokenStream) -> TokenStream {
 /// }
 /// ```
 #[proc_macro_attribute]
-#[cfg(not(test))] // Work around for rust-lang/rust#62127
 pub fn main_rt(args: TokenStream, item: TokenStream) -> TokenStream {
-    entry::main(args, item, false)
+    entry::main(args.into(), item.into(), false).into()
 }
 
 /// Marks async function to be executed by runtime, suitable to test environment.
@@ -288,8 +294,7 @@ pub fn main_rt(args: TokenStream, item: TokenStream) -> TokenStream {
 /// ```
 ///
 /// The `worker_threads` option configures the number of worker threads, and
-/// defaults to the number of cpus on the system. This is the default
-/// flavor.
+/// defaults to the number of cpus on the system.
 ///
 /// Note: The multi-threaded runtime requires the `rt-multi-thread` feature
 /// flag.
@@ -420,7 +425,7 @@ pub fn main_rt(args: TokenStream, item: TokenStream) -> TokenStream {
 /// ```
 #[proc_macro_attribute]
 pub fn test(args: TokenStream, item: TokenStream) -> TokenStream {
-    entry::test(args, item, true)
+    entry::test(args.into(), item.into(), true).into()
 }
 
 /// Marks async function to be executed by runtime, suitable to test environment
@@ -435,7 +440,7 @@ pub fn test(args: TokenStream, item: TokenStream) -> TokenStream {
 /// ```
 #[proc_macro_attribute]
 pub fn test_rt(args: TokenStream, item: TokenStream) -> TokenStream {
-    entry::test(args, item, false)
+    entry::test(args.into(), item.into(), false).into()
 }
 
 /// Always fails with the error message below.

tokio-macros/src/select.rs

@@ -1,7 +1,7 @@
 use proc_macro::{TokenStream, TokenTree};
 use proc_macro2::Span;
 use quote::quote;
-use syn::Ident;
+use syn::{parse::Parser, Ident};
 
 pub(crate) fn declare_output_enum(input: TokenStream) -> TokenStream {
     // passed in is: `(_ _ _)` with one `_` per branch
@@ -46,7 +46,7 @@ pub(crate) fn clean_pattern_macro(input: TokenStream) -> TokenStream {
     // If this isn't a pattern, we return the token stream as-is. The select!
     // macro is using it in a location requiring a pattern, so an error will be
     // emitted there.
-    let mut input: syn::Pat = match syn::parse(input.clone()) {
+    let mut input: syn::Pat = match syn::Pat::parse_single.parse(input.clone()) {
         Ok(it) => it,
         Err(_) => return input,
     };
@@ -58,7 +58,6 @@ pub(crate) fn clean_pattern_macro(input: TokenStream) -> TokenStream {
 // Removes any occurrences of ref or mut in the provided pattern.
 fn clean_pattern(pat: &mut syn::Pat) {
     match pat {
-        syn::Pat::Box(_box) => {}
         syn::Pat::Lit(_literal) => {}
         syn::Pat::Macro(_macro) => {}
         syn::Pat::Path(_path) => {}
@@ -74,27 +73,27 @@ fn clean_pattern(pat: &mut syn::Pat) {
             }
         }
         syn::Pat::Or(or) => {
-            for case in or.cases.iter_mut() {
+            for case in &mut or.cases {
                 clean_pattern(case);
             }
         }
         syn::Pat::Slice(slice) => {
-            for elem in slice.elems.iter_mut() {
+            for elem in &mut slice.elems {
                 clean_pattern(elem);
             }
         }
         syn::Pat::Struct(struct_pat) => {
-            for field in struct_pat.fields.iter_mut() {
+            for field in &mut struct_pat.fields {
                 clean_pattern(&mut field.pat);
             }
         }
         syn::Pat::Tuple(tuple) => {
-            for elem in tuple.elems.iter_mut() {
+            for elem in &mut tuple.elems {
                 clean_pattern(elem);
             }
         }
         syn::Pat::TupleStruct(tuple) => {
-            for elem in tuple.pat.elems.iter_mut() {
+            for elem in &mut tuple.elems {
                 clean_pattern(elem);
             }
         }

tokio-stream/CHANGELOG.md

@@ -1,3 +1,48 @@
+# 0.1.15 (March 14th, 2024)
+
+This release bumps the MSRV of tokio-stream to 1.63.
+
+- docs: fix typo in argument name ([#6389])
+- docs: fix typo in peekable docs ([#6130])
+- docs: link to latest version of tokio-util docs ([#5694])
+- docs: typographic improvements ([#6262])
+- stream: add `StreamExt::peekable` ([#6095])
+
+[#5694]: https://github.com/tokio-rs/tokio/pull/5694
+[#6095]: https://github.com/tokio-rs/tokio/pull/6095
+[#6130]: https://github.com/tokio-rs/tokio/pull/6130
+[#6262]: https://github.com/tokio-rs/tokio/pull/6262
+[#6389]: https://github.com/tokio-rs/tokio/pull/6389
+
+# 0.1.14 (April 26th, 2023)
+
+This bugfix release bumps the minimum version of Tokio to 1.15, which is
+necessary for `timeout_repeating` to compile. ([#5657])
+
+[#5657]: https://github.com/tokio-rs/tokio/pull/5657
+
+# 0.1.13 (April 25th, 2023)
+
+This release bumps the MSRV of tokio-stream to 1.56.
+
+- stream: add "full" feature flag ([#5639])
+- stream: add `StreamExt::timeout_repeating` ([#5577])
+- stream: add `StreamNotifyClose` ([#4851])
+
+[#4851]: https://github.com/tokio-rs/tokio/pull/4851
+[#5577]: https://github.com/tokio-rs/tokio/pull/5577
+[#5639]: https://github.com/tokio-rs/tokio/pull/5639
+
+# 0.1.12 (January 20, 2023)
+
+- time: remove `Unpin` bound on `Throttle` methods ([#5105])
+- time: document that `throttle` operates on ms granularity ([#5101])
+- sync: add `WatchStream::from_changes` ([#5432])
+
+[#5105]: https://github.com/tokio-rs/tokio/pull/5105
+[#5101]: https://github.com/tokio-rs/tokio/pull/5101
+[#5432]: https://github.com/tokio-rs/tokio/pull/5432
+
 # 0.1.11 (October 11, 2022)
 
 - time: allow `StreamExt::chunks_timeout` outside of a runtime ([#5036])

tokio-stream/Cargo.toml

@@ -4,9 +4,9 @@ name = "tokio-stream"
 # - Remove path dependencies
 # - Update CHANGELOG.md.
 # - Create "tokio-stream-0.1.x" git tag.
-version = "0.1.11"
-edition = "2018"
-rust-version = "1.49"
+version = "0.1.15"
+edition = "2021"
+rust-version = "1.63"
 authors = ["Tokio Contributors <[email protected]>"]
 license = "MIT"
 repository = "https://github.com/tokio-rs/tokio"
@@ -18,6 +18,16 @@ categories = ["asynchronous"]
 
 [features]
 default = ["time"]
+
+full = [
+    "time",
+    "net",
+    "io-util",
+    "fs",
+    "sync",
+    "signal"
+]
+
 time = ["tokio/time"]
 net = ["tokio/net"]
 io-util = ["tokio/io-util"]
@@ -27,8 +37,8 @@ signal = ["tokio/signal"]
 
 [dependencies]
 futures-core = { version = "0.3.0" }
-pin-project-lite = "0.2.0"
-tokio = { version = "1.8.0", path = "../tokio", features = ["sync"] }
+pin-project-lite = "0.2.11"
+tokio = { version = "1.15.0", path = "../tokio", features = ["sync"] }
 tokio-util = { version = "0.7.0", path = "../tokio-util", optional = true }
 
 [dev-dependencies]
@@ -38,9 +48,6 @@ parking_lot = "0.12.0"
 tokio-test = { path = "../tokio-test" }
 futures = { version = "0.3", default-features = false }
 
-[target.'cfg(not(target_arch = "wasm32"))'.dev-dependencies]
-proptest = "1"
-
 [package.metadata.docs.rs]
 all-features = true
 rustdoc-args = ["--cfg", "docsrs"]

tokio-stream/LICENSE

@@ -1,25 +1,21 @@
-Copyright (c) 2022 Tokio Contributors
+MIT License
 
-Permission is hereby granted, free of charge, to any
-person obtaining a copy of this software and associated
-documentation files (the "Software"), to deal in the
-Software without restriction, including without
-limitation the rights to use, copy, modify, merge,
-publish, distribute, sublicense, and/or sell copies of
-the Software, and to permit persons to whom the Software
-is furnished to do so, subject to the following
-conditions:
+Copyright (c) Tokio Contributors
 
-The above copyright notice and this permission notice
-shall be included in all copies or substantial portions
-of the Software.
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
 
-THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF
-ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED
-TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
-PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT
-SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
-CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
-OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR
-IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
-DEALINGS IN THE SOFTWARE.
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

tokio-stream/README.md

@@ -0,0 +1,13 @@
+# tokio-stream
+
+Utilities to work with `Stream` and `tokio`.
+
+## License
+
+This project is licensed under the [MIT license](LICENSE).
+
+### Contribution
+
+Unless you explicitly state otherwise, any contribution intentionally submitted
+for inclusion in Tokio by you, shall be licensed as MIT, without any additional
+terms or conditions.

tokio-stream/fuzz/.gitignore

@@ -0,0 +1,4 @@
+target
+corpus
+artifacts
+coverage

tokio-stream/fuzz/Cargo.toml

@@ -0,0 +1,29 @@
+[package]
+name = "tokio-stream-fuzz"
+version = "0.0.0"
+publish = false
+edition = "2021"
+
+[package.metadata]
+cargo-fuzz = true
+
+[dependencies]
+libfuzzer-sys = "0.4"
+tokio-test = { path = "../../tokio-test" }
+
+[dependencies.tokio-stream]
+path = ".."
+
+
+# Prevent this from interfering with workspaces
+[workspace]
+members = ["."]
+
+[profile.release]
+debug = 1
+
+[[bin]]
+name = "fuzz_stream_map"
+path = "fuzz_targets/fuzz_stream_map.rs"
+test = false
+doc = false

tokio-stream/fuzz/fuzz_targets/fuzz_stream_map.rs

@@ -0,0 +1,72 @@
+#![no_main]
+
+use libfuzzer_sys::fuzz_target;
+use std::pin::Pin;
+
+use tokio_stream::{self as stream, Stream, StreamMap};
+use tokio_test::{assert_pending, assert_ready, task};
+
+macro_rules! assert_ready_none {
+    ($($t:tt)*) => {
+        match assert_ready!($($t)*) {
+            None => {}
+            Some(v) => panic!("expected `None`, got `Some({:?})`", v),
+        }
+    };
+}
+
+fn pin_box<T: Stream<Item = U> + 'static, U>(s: T) -> Pin<Box<dyn Stream<Item = U>>> {
+    Box::pin(s)
+}
+
+fuzz_target!(|data: [bool; 64]| {
+    use std::task::{Context, Poll};
+
+    struct DidPoll<T> {
+        did_poll: bool,
+        inner: T,
+    }
+
+    impl<T: Stream + Unpin> Stream for DidPoll<T> {
+        type Item = T::Item;
+
+        fn poll_next(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<T::Item>> {
+            self.did_poll = true;
+            Pin::new(&mut self.inner).poll_next(cx)
+        }
+    }
+
+    // Try the test with each possible length.
+    for len in 0..data.len() {
+        let mut map = task::spawn(StreamMap::new());
+        let mut expect = 0;
+
+        for (i, is_empty) in data[..len].iter().copied().enumerate() {
+            let inner = if is_empty {
+                pin_box(stream::empty::<()>())
+            } else {
+                expect += 1;
+                pin_box(stream::pending::<()>())
+            };
+
+            let stream = DidPoll {
+                did_poll: false,
+                inner,
+            };
+
+            map.insert(i, stream);
+        }
+
+        if expect == 0 {
+            assert_ready_none!(map.poll_next());
+        } else {
+            assert_pending!(map.poll_next());
+
+            assert_eq!(expect, map.values().count());
+
+            for stream in map.values() {
+                assert!(stream.did_poll);
+            }
+        }
+    }
+});

tokio-stream/src/lib.rs

@@ -1,3 +1,4 @@
+#![allow(unknown_lints, unexpected_cfgs)]
 #![allow(
     clippy::cognitive_complexity,
     clippy::large_enum_variant,
@@ -54,7 +55,7 @@
 //!
 //! [async-stream]: https://docs.rs/async-stream
 //!
-//! # Conversion to and from AsyncRead/AsyncWrite
+//! # Conversion to and from `AsyncRead`/`AsyncWrite`
 //!
 //! It is often desirable to convert a `Stream` into an [`AsyncRead`],
 //! especially when dealing with plaintext formats streamed over the network.
@@ -63,16 +64,19 @@
 //! [`tokio-util`] provides the [`StreamReader`] and [`ReaderStream`]
 //! types when the io feature is enabled.
 //!
-//! [`tokio-util`]: https://docs.rs/tokio-util/0.4/tokio_util/codec/index.html
-//! [`tokio::io`]: https://docs.rs/tokio/1.0/tokio/io/index.html
-//! [`AsyncRead`]: https://docs.rs/tokio/1.0/tokio/io/trait.AsyncRead.html
-//! [`AsyncWrite`]: https://docs.rs/tokio/1.0/tokio/io/trait.AsyncWrite.html
-//! [`ReaderStream`]: https://docs.rs/tokio-util/0.4/tokio_util/io/struct.ReaderStream.html
-//! [`StreamReader`]: https://docs.rs/tokio-util/0.4/tokio_util/io/struct.StreamReader.html
+//! [`tokio-util`]: https://docs.rs/tokio-util/latest/tokio_util/codec/index.html
+//! [`tokio::io`]: https://docs.rs/tokio/latest/tokio/io/index.html
+//! [`AsyncRead`]: https://docs.rs/tokio/latest/tokio/io/trait.AsyncRead.html
+//! [`AsyncWrite`]: https://docs.rs/tokio/latest/tokio/io/trait.AsyncWrite.html
+//! [`ReaderStream`]: https://docs.rs/tokio-util/latest/tokio_util/io/struct.ReaderStream.html
+//! [`StreamReader`]: https://docs.rs/tokio-util/latest/tokio_util/io/struct.StreamReader.html
 
 #[macro_use]
 mod macros;
 
+mod poll_fn;
+pub(crate) use poll_fn::poll_fn;
+
 pub mod wrappers;
 
 mod stream_ext;
@@ -96,5 +100,8 @@ pub use pending::{pending, Pending};
 mod stream_map;
 pub use stream_map::StreamMap;
 
+mod stream_close;
+pub use stream_close::StreamNotifyClose;
+
 #[doc(no_inline)]
 pub use futures_core::Stream;

tokio-stream/src/once.rs

@@ -35,7 +35,7 @@ impl<I> Unpin for Once<I> {}
 /// ```
 pub fn once<T>(value: T) -> Once<T> {
     Once {
-        iter: crate::iter(Some(value).into_iter()),
+        iter: crate::iter(Some(value)),
     }
 }
 

tokio-stream/src/poll_fn.rs

@@ -0,0 +1,35 @@
+use std::future::Future;
+use std::pin::Pin;
+use std::task::{Context, Poll};
+
+pub(crate) struct PollFn<F> {
+    f: F,
+}
+
+pub(crate) fn poll_fn<T, F>(f: F) -> PollFn<F>
+where
+    F: FnMut(&mut Context<'_>) -> Poll<T>,
+{
+    PollFn { f }
+}
+
+impl<T, F> Future for PollFn<F>
+where
+    F: FnMut(&mut Context<'_>) -> Poll<T>,
+{
+    type Output = T;
+
+    fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<T> {
+        // Safety: We never construct a `Pin<&mut F>` anywhere, so accessing `f`
+        // mutably in an unpinned way is sound.
+        //
+        // This use of unsafe cannot be replaced with the pin-project macro
+        // because:
+        //  * If we put `#[pin]` on the field, then it gives us a `Pin<&mut F>`,
+        //    which we can't use to call the closure.
+        //  * If we don't put `#[pin]` on the field, then it makes `PollFn` be
+        //    unconditionally `Unpin`, which we also don't want.
+        let me = unsafe { Pin::into_inner_unchecked(self) };
+        (me.f)(cx)
+    }
+}

tokio-stream/src/stream_close.rs

@@ -0,0 +1,93 @@
+use crate::Stream;
+use pin_project_lite::pin_project;
+use std::pin::Pin;
+use std::task::{Context, Poll};
+
+pin_project! {
+    /// A `Stream` that wraps the values in an `Option`.
+    ///
+    /// Whenever the wrapped stream yields an item, this stream yields that item
+    /// wrapped in `Some`. When the inner stream ends, then this stream first
+    /// yields a `None` item, and then this stream will also end.
+    ///
+    /// # Example
+    ///
+    /// Using `StreamNotifyClose` to handle closed streams with `StreamMap`.
+    ///
+    /// ```
+    /// use tokio_stream::{StreamExt, StreamMap, StreamNotifyClose};
+    ///
+    /// #[tokio::main]
+    /// async fn main() {
+    ///     let mut map = StreamMap::new();
+    ///     let stream = StreamNotifyClose::new(tokio_stream::iter(vec![0, 1]));
+    ///     let stream2 = StreamNotifyClose::new(tokio_stream::iter(vec![0, 1]));
+    ///     map.insert(0, stream);
+    ///     map.insert(1, stream2);
+    ///     while let Some((key, val)) = map.next().await {
+    ///         match val {
+    ///             Some(val) => println!("got {val:?} from stream {key:?}"),
+    ///             None => println!("stream {key:?} closed"),
+    ///         }
+    ///     }
+    /// }
+    /// ```
+    #[must_use = "streams do nothing unless polled"]
+    pub struct StreamNotifyClose<S> {
+        #[pin]
+        inner: Option<S>,
+    }
+}
+
+impl<S> StreamNotifyClose<S> {
+    /// Create a new `StreamNotifyClose`.
+    pub fn new(stream: S) -> Self {
+        Self {
+            inner: Some(stream),
+        }
+    }
+
+    /// Get back the inner `Stream`.
+    ///
+    /// Returns `None` if the stream has reached its end.
+    pub fn into_inner(self) -> Option<S> {
+        self.inner
+    }
+}
+
+impl<S> Stream for StreamNotifyClose<S>
+where
+    S: Stream,
+{
+    type Item = Option<S::Item>;
+
+    fn poll_next(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
+        // We can't invoke poll_next after it ended, so we unset the inner stream as a marker.
+        match self
+            .as_mut()
+            .project()
+            .inner
+            .as_pin_mut()
+            .map(|stream| S::poll_next(stream, cx))
+        {
+            Some(Poll::Ready(Some(item))) => Poll::Ready(Some(Some(item))),
+            Some(Poll::Ready(None)) => {
+                self.project().inner.set(None);
+                Poll::Ready(Some(None))
+            }
+            Some(Poll::Pending) => Poll::Pending,
+            None => Poll::Ready(None),
+        }
+    }
+
+    #[inline]
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        if let Some(inner) = &self.inner {
+            // We always return +1 because when there's stream there's atleast one more item.
+            let (l, u) = inner.size_hint();
+            (l.saturating_add(1), u.and_then(|u| u.checked_add(1)))
+        } else {
+            (0, Some(0))
+        }
+    }
+}

tokio-stream/src/stream_ext.rs

@@ -55,10 +55,15 @@ use then::Then;
 mod try_next;
 use try_next::TryNext;
 
+mod peekable;
+use peekable::Peekable;
+
 cfg_time! {
     pub(crate) mod timeout;
+    pub(crate) mod timeout_repeating;
     use timeout::Timeout;
-    use tokio::time::Duration;
+    use timeout_repeating::TimeoutRepeating;
+    use tokio::time::{Duration, Interval};
     mod throttle;
     use throttle::{throttle, Throttle};
     mod chunks_timeout;
@@ -846,8 +851,7 @@ pub trait StreamExt: Stream {
     ///
     /// `collect` streams all values, awaiting as needed. Values are pushed into
     /// a collection. A number of different target collection types are
-    /// supported, including [`Vec`](std::vec::Vec),
-    /// [`String`](std::string::String), and [`Bytes`].
+    /// supported, including [`Vec`], [`String`], and [`Bytes`].
     ///
     /// [`Bytes`]: https://docs.rs/bytes/0.6.0/bytes/struct.Bytes.html
     ///
@@ -924,7 +928,9 @@ pub trait StreamExt: Stream {
     /// If the wrapped stream yields a value before the deadline is reached, the
     /// value is returned. Otherwise, an error is returned. The caller may decide
     /// to continue consuming the stream and will eventually get the next source
-    /// stream value once it becomes available.
+    /// stream value once it becomes available. See
+    /// [`timeout_repeating`](StreamExt::timeout_repeating) for an alternative
+    /// where the timeouts will repeat.
     ///
     /// # Notes
     ///
@@ -971,7 +977,26 @@ pub trait StreamExt: Stream {
     /// assert_eq!(int_stream.try_next().await, Ok(None));
     /// # }
     /// ```
-    #[cfg(all(feature = "time"))]
+    ///
+    /// Once a timeout error is received, no further events will be received
+    /// unless the wrapped stream yields a value (timeouts do not repeat).
+    ///
+    /// ```
+    /// # #[tokio::main(flavor = "current_thread", start_paused = true)]
+    /// # async fn main() {
+    /// use tokio_stream::{StreamExt, wrappers::IntervalStream};
+    /// use std::time::Duration;
+    /// let interval_stream = IntervalStream::new(tokio::time::interval(Duration::from_millis(100)));
+    /// let timeout_stream = interval_stream.timeout(Duration::from_millis(10));
+    /// tokio::pin!(timeout_stream);
+    ///
+    /// // Only one timeout will be received between values in the source stream.
+    /// assert!(timeout_stream.try_next().await.is_ok());
+    /// assert!(timeout_stream.try_next().await.is_err(), "expected one timeout");
+    /// assert!(timeout_stream.try_next().await.is_ok(), "expected no more timeouts");
+    /// # }
+    /// ```
+    #[cfg(feature = "time")]
     #[cfg_attr(docsrs, doc(cfg(feature = "time")))]
     fn timeout(self, duration: Duration) -> Timeout<Self>
     where
@@ -980,6 +1005,94 @@ pub trait StreamExt: Stream {
         Timeout::new(self, duration)
     }
 
+    /// Applies a per-item timeout to the passed stream.
+    ///
+    /// `timeout_repeating()` takes an [`Interval`] that controls the time each
+    /// element of the stream has to complete before timing out.
+    ///
+    /// If the wrapped stream yields a value before the deadline is reached, the
+    /// value is returned. Otherwise, an error is returned. The caller may decide
+    /// to continue consuming the stream and will eventually get the next source
+    /// stream value once it becomes available. Unlike `timeout()`, if no value
+    /// becomes available before the deadline is reached, additional errors are
+    /// returned at the specified interval. See [`timeout`](StreamExt::timeout)
+    /// for an alternative where the timeouts do not repeat.
+    ///
+    /// # Notes
+    ///
+    /// This function consumes the stream passed into it and returns a
+    /// wrapped version of it.
+    ///
+    /// Polling the returned stream will continue to poll the inner stream even
+    /// if one or more items time out.
+    ///
+    /// # Examples
+    ///
+    /// Suppose we have a stream `int_stream` that yields 3 numbers (1, 2, 3):
+    ///
+    /// ```
+    /// # #[tokio::main]
+    /// # async fn main() {
+    /// use tokio_stream::{self as stream, StreamExt};
+    /// use std::time::Duration;
+    /// # let int_stream = stream::iter(1..=3);
+    ///
+    /// let int_stream = int_stream.timeout_repeating(tokio::time::interval(Duration::from_secs(1)));
+    /// tokio::pin!(int_stream);
+    ///
+    /// // When no items time out, we get the 3 elements in succession:
+    /// assert_eq!(int_stream.try_next().await, Ok(Some(1)));
+    /// assert_eq!(int_stream.try_next().await, Ok(Some(2)));
+    /// assert_eq!(int_stream.try_next().await, Ok(Some(3)));
+    /// assert_eq!(int_stream.try_next().await, Ok(None));
+    ///
+    /// // If the second item times out, we get an error and continue polling the stream:
+    /// # let mut int_stream = stream::iter(vec![Ok(1), Err(()), Ok(2), Ok(3)]);
+    /// assert_eq!(int_stream.try_next().await, Ok(Some(1)));
+    /// assert!(int_stream.try_next().await.is_err());
+    /// assert_eq!(int_stream.try_next().await, Ok(Some(2)));
+    /// assert_eq!(int_stream.try_next().await, Ok(Some(3)));
+    /// assert_eq!(int_stream.try_next().await, Ok(None));
+    ///
+    /// // If we want to stop consuming the source stream the first time an
+    /// // element times out, we can use the `take_while` operator:
+    /// # let int_stream = stream::iter(vec![Ok(1), Err(()), Ok(2), Ok(3)]);
+    /// let mut int_stream = int_stream.take_while(Result::is_ok);
+    ///
+    /// assert_eq!(int_stream.try_next().await, Ok(Some(1)));
+    /// assert_eq!(int_stream.try_next().await, Ok(None));
+    /// # }
+    /// ```
+    ///
+    /// Timeout errors will be continuously produced at the specified interval
+    /// until the wrapped stream yields a value.
+    ///
+    /// ```
+    /// # #[tokio::main(flavor = "current_thread", start_paused = true)]
+    /// # async fn main() {
+    /// use tokio_stream::{StreamExt, wrappers::IntervalStream};
+    /// use std::time::Duration;
+    /// let interval_stream = IntervalStream::new(tokio::time::interval(Duration::from_millis(23)));
+    /// let timeout_stream = interval_stream.timeout_repeating(tokio::time::interval(Duration::from_millis(9)));
+    /// tokio::pin!(timeout_stream);
+    ///
+    /// // Multiple timeouts will be received between values in the source stream.
+    /// assert!(timeout_stream.try_next().await.is_ok());
+    /// assert!(timeout_stream.try_next().await.is_err(), "expected one timeout");
+    /// assert!(timeout_stream.try_next().await.is_err(), "expected a second timeout");
+    /// // Will eventually receive another value from the source stream...
+    /// assert!(timeout_stream.try_next().await.is_ok(), "expected non-timeout");
+    /// # }
+    /// ```
+    #[cfg(feature = "time")]
+    #[cfg_attr(docsrs, doc(cfg(feature = "time")))]
+    fn timeout_repeating(self, interval: Interval) -> TimeoutRepeating<Self>
+    where
+        Self: Sized,
+    {
+        TimeoutRepeating::new(self, interval)
+    }
+
     /// Slows down a stream by enforcing a delay between items.
     ///
     /// The underlying timer behind this utility has a granularity of one millisecond.
@@ -1001,7 +1114,7 @@ pub trait StreamExt: Stream {
     /// }
     /// # }
     /// ```
-    #[cfg(all(feature = "time"))]
+    #[cfg(feature = "time")]
     #[cfg_attr(docsrs, doc(cfg(feature = "time")))]
     fn throttle(self, duration: Duration) -> Throttle<Self>
     where
@@ -1066,6 +1179,31 @@ pub trait StreamExt: Stream {
         assert!(max_size > 0, "`max_size` must be non-zero.");
         ChunksTimeout::new(self, max_size, duration)
     }
+
+    /// Turns the stream into a peekable stream, whose next element can be peeked at without being
+    /// consumed.
+    /// ```rust
+    /// use tokio_stream::{self as stream, StreamExt};
+    ///
+    /// #[tokio::main]
+    /// # async fn _unused() {}
+    /// # #[tokio::main(flavor = "current_thread", start_paused = true)]
+    /// async fn main() {
+    ///     let iter = vec![1, 2, 3, 4].into_iter();
+    ///     let mut stream = stream::iter(iter).peekable();
+    ///
+    ///     assert_eq!(*stream.peek().await.unwrap(), 1);
+    ///     assert_eq!(*stream.peek().await.unwrap(), 1);
+    ///     assert_eq!(stream.next().await.unwrap(), 1);
+    ///     assert_eq!(*stream.peek().await.unwrap(), 2);
+    /// }
+    /// ```
+    fn peekable(self) -> Peekable<Self>
+    where
+        Self: Sized,
+    {
+        Peekable::new(self)
+    }
 }
 
 impl<St: ?Sized> StreamExt for St where St: Stream {}

tokio-stream/src/stream_ext/collect.rs

@@ -26,7 +26,7 @@ pin_project! {
     }
 }
 
-/// Convert from a [`Stream`](crate::Stream).
+/// Convert from a [`Stream`].
 ///
 /// This trait is not intended to be used directly. Instead, call
 /// [`StreamExt::collect()`](super::StreamExt::collect).

tokio-stream/src/stream_ext/merge.rs

@@ -66,25 +66,23 @@ where
     T: Stream,
     U: Stream<Item = T::Item>,
 {
-    use Poll::*;
-
     let mut done = true;
 
     match first.poll_next(cx) {
-        Ready(Some(val)) => return Ready(Some(val)),
-        Ready(None) => {}
-        Pending => done = false,
+        Poll::Ready(Some(val)) => return Poll::Ready(Some(val)),
+        Poll::Ready(None) => {}
+        Poll::Pending => done = false,
     }
 
     match second.poll_next(cx) {
-        Ready(Some(val)) => return Ready(Some(val)),
-        Ready(None) => {}
-        Pending => done = false,
+        Poll::Ready(Some(val)) => return Poll::Ready(Some(val)),
+        Poll::Ready(None) => {}
+        Poll::Pending => done = false,
     }
 
     if done {
-        Ready(None)
+        Poll::Ready(None)
     } else {
-        Pending
+        Poll::Pending
     }
 }

tokio-stream/src/stream_ext/peekable.rs

@@ -0,0 +1,50 @@
+use std::pin::Pin;
+use std::task::{Context, Poll};
+
+use futures_core::Stream;
+use pin_project_lite::pin_project;
+
+use crate::stream_ext::Fuse;
+use crate::StreamExt;
+
+pin_project! {
+    /// Stream returned by the [`chain`](super::StreamExt::peekable) method.
+    pub struct Peekable<T: Stream> {
+        peek: Option<T::Item>,
+        #[pin]
+        stream: Fuse<T>,
+    }
+}
+
+impl<T: Stream> Peekable<T> {
+    pub(crate) fn new(stream: T) -> Self {
+        let stream = stream.fuse();
+        Self { peek: None, stream }
+    }
+
+    /// Peek at the next item in the stream.
+    pub async fn peek(&mut self) -> Option<&T::Item>
+    where
+        T: Unpin,
+    {
+        if let Some(ref it) = self.peek {
+            Some(it)
+        } else {
+            self.peek = self.next().await;
+            self.peek.as_ref()
+        }
+    }
+}
+
+impl<T: Stream> Stream for Peekable<T> {
+    type Item = T::Item;
+
+    fn poll_next(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
+        let this = self.project();
+        if let Some(it) = this.peek.take() {
+            Poll::Ready(Some(it))
+        } else {
+            this.stream.poll_next(cx)
+        }
+    }
+}

tokio-stream/src/stream_ext/take.rs

@@ -64,11 +64,11 @@ where
 
         let (lower, upper) = self.stream.size_hint();
 
-        let lower = cmp::min(lower, self.remaining as usize);
+        let lower = cmp::min(lower, self.remaining);
 
         let upper = match upper {
-            Some(x) if x < self.remaining as usize => Some(x),
-            _ => Some(self.remaining as usize),
+            Some(x) if x < self.remaining => Some(x),
+            _ => Some(self.remaining),
         };
 
         (lower, upper)

tokio-stream/src/stream_ext/timeout.rs

@@ -23,7 +23,7 @@ pin_project! {
     }
 }
 
-/// Error returned by `Timeout`.
+/// Error returned by `Timeout` and `TimeoutRepeating`.
 #[derive(Debug, PartialEq, Eq)]
 pub struct Elapsed(());
 

tokio-stream/src/stream_ext/timeout_repeating.rs

@@ -0,0 +1,56 @@
+use crate::stream_ext::Fuse;
+use crate::{Elapsed, Stream};
+use tokio::time::Interval;
+
+use core::pin::Pin;
+use core::task::{Context, Poll};
+use pin_project_lite::pin_project;
+
+pin_project! {
+    /// Stream returned by the [`timeout_repeating`](super::StreamExt::timeout_repeating) method.
+    #[must_use = "streams do nothing unless polled"]
+    #[derive(Debug)]
+    pub struct TimeoutRepeating<S> {
+        #[pin]
+        stream: Fuse<S>,
+        #[pin]
+        interval: Interval,
+    }
+}
+
+impl<S: Stream> TimeoutRepeating<S> {
+    pub(super) fn new(stream: S, interval: Interval) -> Self {
+        TimeoutRepeating {
+            stream: Fuse::new(stream),
+            interval,
+        }
+    }
+}
+
+impl<S: Stream> Stream for TimeoutRepeating<S> {
+    type Item = Result<S::Item, Elapsed>;
+
+    fn poll_next(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
+        let mut me = self.project();
+
+        match me.stream.poll_next(cx) {
+            Poll::Ready(v) => {
+                if v.is_some() {
+                    me.interval.reset();
+                }
+                return Poll::Ready(v.map(Ok));
+            }
+            Poll::Pending => {}
+        };
+
+        ready!(me.interval.poll_tick(cx));
+        Poll::Ready(Some(Err(Elapsed::new())))
+    }
+
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        let (lower, _) = self.stream.size_hint();
+
+        // The timeout stream may insert an error an infinite number of times.
+        (lower, None)
+    }
+}

tokio-stream/src/stream_map.rs

@@ -1,4 +1,4 @@
-use crate::Stream;
+use crate::{poll_fn, Stream};
 
 use std::borrow::Borrow;
 use std::hash::Hash;
@@ -42,10 +42,18 @@ use std::task::{Context, Poll};
 /// to be merged, it may be advisable to use tasks sending values on a shared
 /// [`mpsc`] channel.
 ///
+/// # Notes
+///
+/// `StreamMap` removes finished streams automatically, without alerting the user.
+/// In some scenarios, the caller would want to know on closed streams.
+/// To do this, use [`StreamNotifyClose`] as a wrapper to your stream.
+/// It will return None when the stream is closed.
+///
 /// [`StreamExt::merge`]: crate::StreamExt::merge
 /// [`mpsc`]: https://docs.rs/tokio/1.0/tokio/sync/mpsc/index.html
 /// [`pin!`]: https://docs.rs/tokio/1.0/tokio/macro.pin.html
 /// [`Box::pin`]: std::boxed::Box::pin
+/// [`StreamNotifyClose`]: crate::StreamNotifyClose
 ///
 /// # Examples
 ///
@@ -170,6 +178,28 @@ use std::task::{Context, Poll};
 ///     }
 /// }
 /// ```
+///
+/// Using `StreamNotifyClose` to handle closed streams with `StreamMap`.
+///
+/// ```
+/// use tokio_stream::{StreamExt, StreamMap, StreamNotifyClose};
+///
+/// #[tokio::main]
+/// async fn main() {
+///     let mut map = StreamMap::new();
+///     let stream = StreamNotifyClose::new(tokio_stream::iter(vec![0, 1]));
+///     let stream2 = StreamNotifyClose::new(tokio_stream::iter(vec![0, 1]));
+///     map.insert(0, stream);
+///     map.insert(1, stream2);
+///     while let Some((key, val)) = map.next().await {
+///         match val {
+///             Some(val) => println!("got {val:?} from stream {key:?}"),
+///             None => println!("stream {key:?} closed"),
+///         }
+///     }
+/// }
+/// ```
+
 #[derive(Debug)]
 pub struct StreamMap<K, V> {
     /// Streams stored in the map
@@ -179,7 +209,7 @@ pub struct StreamMap<K, V> {
 impl<K, V> StreamMap<K, V> {
     /// An iterator visiting all key-value pairs in arbitrary order.
     ///
-    /// The iterator element type is &'a (K, V).
+    /// The iterator element type is `&'a (K, V)`.
     ///
     /// # Examples
     ///
@@ -202,7 +232,7 @@ impl<K, V> StreamMap<K, V> {
 
     /// An iterator visiting all key-value pairs mutably in arbitrary order.
     ///
-    /// The iterator element type is &'a mut (K, V).
+    /// The iterator element type is `&'a mut (K, V)`.
     ///
     /// # Examples
     ///
@@ -259,7 +289,7 @@ impl<K, V> StreamMap<K, V> {
 
     /// Returns an iterator visiting all keys in arbitrary order.
     ///
-    /// The iterator element type is &'a K.
+    /// The iterator element type is `&'a K`.
     ///
     /// # Examples
     ///
@@ -282,7 +312,7 @@ impl<K, V> StreamMap<K, V> {
 
     /// An iterator visiting all values in arbitrary order.
     ///
-    /// The iterator element type is &'a V.
+    /// The iterator element type is `&'a V`.
     ///
     /// # Examples
     ///
@@ -305,7 +335,7 @@ impl<K, V> StreamMap<K, V> {
 
     /// An iterator visiting all values mutably in arbitrary order.
     ///
-    /// The iterator element type is &'a mut V.
+    /// The iterator element type is `&'a mut V`.
     ///
     /// # Examples
     ///
@@ -437,10 +467,10 @@ impl<K, V> StreamMap<K, V> {
     /// assert!(map.remove(&1).is_some());
     /// assert!(map.remove(&1).is_none());
     /// ```
-    pub fn remove<Q: ?Sized>(&mut self, k: &Q) -> Option<V>
+    pub fn remove<Q>(&mut self, k: &Q) -> Option<V>
     where
         K: Borrow<Q>,
-        Q: Hash + Eq,
+        Q: Hash + Eq + ?Sized,
     {
         for i in 0..self.entries.len() {
             if self.entries[i].0.borrow() == k {
@@ -466,10 +496,10 @@ impl<K, V> StreamMap<K, V> {
     /// assert_eq!(map.contains_key(&1), true);
     /// assert_eq!(map.contains_key(&2), false);
     /// ```
-    pub fn contains_key<Q: ?Sized>(&self, k: &Q) -> bool
+    pub fn contains_key<Q>(&self, k: &Q) -> bool
     where
         K: Borrow<Q>,
-        Q: Hash + Eq,
+        Q: Hash + Eq + ?Sized,
     {
         for i in 0..self.entries.len() {
             if self.entries[i].0.borrow() == k {
@@ -488,8 +518,6 @@ where
 {
     /// Polls the next value, includes the vec entry index
     fn poll_next_entry(&mut self, cx: &mut Context<'_>) -> Poll<Option<(usize, V::Item)>> {
-        use Poll::*;
-
         let start = self::rand::thread_rng_n(self.entries.len() as u32) as usize;
         let mut idx = start;
 
@@ -497,8 +525,8 @@ where
             let (_, stream) = &mut self.entries[idx];
 
             match Pin::new(stream).poll_next(cx) {
-                Ready(Some(val)) => return Ready(Some((idx, val))),
-                Ready(None) => {
+                Poll::Ready(Some(val)) => return Poll::Ready(Some((idx, val))),
+                Poll::Ready(None) => {
                     // Remove the entry
                     self.entries.swap_remove(idx);
 
@@ -512,7 +540,7 @@ where
                         idx = idx.wrapping_add(1) % self.entries.len();
                     }
                 }
-                Pending => {
+                Poll::Pending => {
                     idx = idx.wrapping_add(1) % self.entries.len();
                 }
             }
@@ -520,9 +548,9 @@ where
 
         // If the map is empty, then the stream is complete.
         if self.entries.is_empty() {
-            Ready(None)
+            Poll::Ready(None)
         } else {
-            Pending
+            Poll::Pending
         }
     }
 }
@@ -533,6 +561,110 @@ impl<K, V> Default for StreamMap<K, V> {
     }
 }
 
+impl<K, V> StreamMap<K, V>
+where
+    K: Clone + Unpin,
+    V: Stream + Unpin,
+{
+    /// Receives multiple items on this [`StreamMap`], extending the provided `buffer`.
+    ///
+    /// This method returns the number of items that is appended to the `buffer`.
+    ///
+    /// Note that this method does not guarantee that exactly `limit` items
+    /// are received. Rather, if at least one item is available, it returns
+    /// as many items as it can up to the given limit. This method returns
+    /// zero only if the `StreamMap` is empty (or if `limit` is zero).
+    ///
+    /// # Cancel safety
+    ///
+    /// This method is cancel safe. If `next_many` is used as the event in a
+    /// [`tokio::select!`](tokio::select) statement and some other branch
+    /// completes first, it is guaranteed that no items were received on any of
+    /// the underlying streams.
+    pub async fn next_many(&mut self, buffer: &mut Vec<(K, V::Item)>, limit: usize) -> usize {
+        poll_fn(|cx| self.poll_next_many(cx, buffer, limit)).await
+    }
+
+    /// Polls to receive multiple items on this `StreamMap`, extending the provided `buffer`.
+    ///
+    /// This method returns:
+    /// * `Poll::Pending` if no items are available but the `StreamMap` is not empty.
+    /// * `Poll::Ready(count)` where `count` is the number of items successfully received and
+    ///   stored in `buffer`. This can be less than, or equal to, `limit`.
+    /// * `Poll::Ready(0)` if `limit` is set to zero or when the `StreamMap` is empty.
+    ///
+    /// Note that this method does not guarantee that exactly `limit` items
+    /// are received. Rather, if at least one item is available, it returns
+    /// as many items as it can up to the given limit. This method returns
+    /// zero only if the `StreamMap` is empty (or if `limit` is zero).
+    pub fn poll_next_many(
+        &mut self,
+        cx: &mut Context<'_>,
+        buffer: &mut Vec<(K, V::Item)>,
+        limit: usize,
+    ) -> Poll<usize> {
+        if limit == 0 || self.entries.is_empty() {
+            return Poll::Ready(0);
+        }
+
+        let mut added = 0;
+
+        let start = self::rand::thread_rng_n(self.entries.len() as u32) as usize;
+        let mut idx = start;
+
+        while added < limit {
+            // Indicates whether at least one stream returned a value when polled or not
+            let mut should_loop = false;
+
+            for _ in 0..self.entries.len() {
+                let (_, stream) = &mut self.entries[idx];
+
+                match Pin::new(stream).poll_next(cx) {
+                    Poll::Ready(Some(val)) => {
+                        added += 1;
+
+                        let key = self.entries[idx].0.clone();
+                        buffer.push((key, val));
+
+                        should_loop = true;
+
+                        idx = idx.wrapping_add(1) % self.entries.len();
+                    }
+                    Poll::Ready(None) => {
+                        // Remove the entry
+                        self.entries.swap_remove(idx);
+
+                        // Check if this was the last entry, if so the cursor needs
+                        // to wrap
+                        if idx == self.entries.len() {
+                            idx = 0;
+                        } else if idx < start && start <= self.entries.len() {
+                            // The stream being swapped into the current index has
+                            // already been polled, so skip it.
+                            idx = idx.wrapping_add(1) % self.entries.len();
+                        }
+                    }
+                    Poll::Pending => {
+                        idx = idx.wrapping_add(1) % self.entries.len();
+                    }
+                }
+            }
+
+            if !should_loop {
+                break;
+            }
+        }
+
+        if added > 0 {
+            Poll::Ready(added)
+        } else if self.entries.is_empty() {
+            Poll::Ready(0)
+        } else {
+            Poll::Pending
+        }
+    }
+}
+
 impl<K, V> Stream for StreamMap<K, V>
 where
     K: Clone + Unpin,
@@ -568,7 +700,7 @@ where
     }
 }
 
-impl<K, V> std::iter::FromIterator<(K, V)> for StreamMap<K, V>
+impl<K, V> FromIterator<(K, V)> for StreamMap<K, V>
 where
     K: Hash + Eq,
 {
@@ -630,9 +762,9 @@ mod rand {
 
     /// Fast random number generate
     ///
-    /// Implement xorshift64+: 2 32-bit xorshift sequences added together.
+    /// Implement `xorshift64+`: 2 32-bit `xorshift` sequences added together.
     /// Shift triplet `[17,7,16]` was calculated as indicated in Marsaglia's
-    /// Xorshift paper: <https://www.jstatsoft.org/article/view/v008i14/xorshift.pdf>
+    /// `Xorshift` paper: <https://www.jstatsoft.org/article/view/v008i14/xorshift.pdf>
     /// This generator passes the SmallCrush suite, part of TestU01 framework:
     /// <http://simul.iro.umontreal.ca/testu01/tu01.html>
     #[derive(Debug)]

tokio-stream/src/wrappers/interval.rs

@@ -33,7 +33,7 @@ impl Stream for IntervalStream {
     }
 
     fn size_hint(&self) -> (usize, Option<usize>) {
-        (std::usize::MAX, None)
+        (usize::MAX, None)
     }
 }
 

tokio-stream/src/wrappers/lines.rs

@@ -30,7 +30,6 @@ impl<R> LinesStream<R> {
     }
 
     /// Obtain a pinned reference to the inner `Lines<R>`.
-    #[allow(clippy::wrong_self_convention)] // https://github.com/rust-lang/rust-clippy/issues/4546
     pub fn as_pin_mut(self: Pin<&mut Self>) -> Pin<&mut Lines<R>> {
         self.project().inner
     }

tokio-stream/src/wrappers/mpsc_bounded.rs

@@ -34,7 +34,7 @@ impl<T> ReceiverStream<T> {
     ///
     /// [`Permit`]: struct@tokio::sync::mpsc::Permit
     pub fn close(&mut self) {
-        self.inner.close()
+        self.inner.close();
     }
 }
 

tokio-stream/src/wrappers/mpsc_unbounded.rs

@@ -28,7 +28,7 @@ impl<T> UnboundedReceiverStream<T> {
     /// This prevents any further messages from being sent on the channel while
     /// still enabling the receiver to drain messages that are buffered.
     pub fn close(&mut self) {
-        self.inner.close()
+        self.inner.close();
     }
 }
 

tokio-stream/src/wrappers/signal_unix.rs

@@ -15,8 +15,8 @@ pub struct SignalStream {
 
 impl SignalStream {
     /// Create a new `SignalStream`.
-    pub fn new(interval: Signal) -> Self {
-        Self { inner: interval }
+    pub fn new(signal: Signal) -> Self {
+        Self { inner: signal }
     }
 
     /// Get back the inner `Signal`.

tokio-stream/src/wrappers/split.rs

@@ -30,7 +30,6 @@ impl<R> SplitStream<R> {
     }
 
     /// Obtain a pinned reference to the inner `Split<R>`.
-    #[allow(clippy::wrong_self_convention)] // https://github.com/rust-lang/rust-clippy/issues/4546
     pub fn as_pin_mut(self: Pin<&mut Self>) -> Pin<&mut Split<R>> {
         self.project().inner
     }

tokio-stream/src/wrappers/watch.rs

@@ -10,8 +10,9 @@ use tokio::sync::watch::error::RecvError;
 
 /// A wrapper around [`tokio::sync::watch::Receiver`] that implements [`Stream`].
 ///
-/// This stream will always start by yielding the current value when the WatchStream is polled,
-/// regardless of whether it was the initial value or sent afterwards.
+/// This stream will start by yielding the current value when the `WatchStream` is polled,
+/// regardless of whether it was the initial value or sent afterwards,
+/// unless you use [`WatchStream<T>::from_changes`].
 ///
 /// # Examples
 ///
@@ -40,6 +41,28 @@ use tokio::sync::watch::error::RecvError;
 /// let (tx, rx) = watch::channel("hello");
 /// let mut rx = WatchStream::new(rx);
 ///
+/// // existing rx output with "hello" is ignored here
+///
+/// tx.send("goodbye").unwrap();
+/// assert_eq!(rx.next().await, Some("goodbye"));
+/// # }
+/// ```
+///
+/// Example with [`WatchStream<T>::from_changes`]:
+///
+/// ```
+/// # #[tokio::main]
+/// # async fn main() {
+/// use futures::future::FutureExt;
+/// use tokio::sync::watch;
+/// use tokio_stream::{StreamExt, wrappers::WatchStream};
+///
+/// let (tx, rx) = watch::channel("hello");
+/// let mut rx = WatchStream::from_changes(rx);
+///
+/// // no output from rx is available at this point - let's check this:
+/// assert!(rx.next().now_or_never().is_none());
+///
 /// tx.send("goodbye").unwrap();
 /// assert_eq!(rx.next().await, Some("goodbye"));
 /// # }
@@ -66,6 +89,13 @@ impl<T: 'static + Clone + Send + Sync> WatchStream<T> {
             inner: ReusableBoxFuture::new(async move { (Ok(()), rx) }),
         }
     }
+
+    /// Create a new `WatchStream` that waits for the value to be changed.
+    pub fn from_changes(rx: Receiver<T>) -> Self {
+        Self {
+            inner: ReusableBoxFuture::new(make_future(rx)),
+        }
+    }
 }
 
 impl<T: Clone + 'static + Send + Sync> Stream for WatchStream<T> {

tokio-stream/tests/async_send_sync.rs

@@ -15,18 +15,21 @@ fn require_unpin<T: Unpin>(_t: &T) {}
 #[allow(dead_code)]
 struct Invalid;
 
+#[allow(unused)]
 trait AmbiguousIfSend<A> {
     fn some_item(&self) {}
 }
 impl<T: ?Sized> AmbiguousIfSend<()> for T {}
 impl<T: ?Sized + Send> AmbiguousIfSend<Invalid> for T {}
 
+#[allow(unused)]
 trait AmbiguousIfSync<A> {
     fn some_item(&self) {}
 }
 impl<T: ?Sized> AmbiguousIfSync<()> for T {}
 impl<T: ?Sized + Sync> AmbiguousIfSync<Invalid> for T {}
 
+#[allow(unused)]
 trait AmbiguousIfUnpin<A> {
     fn some_item(&self) {}
 }

tokio-stream/tests/stream_close.rs

@@ -0,0 +1,11 @@
+use tokio_stream::{StreamExt, StreamNotifyClose};
+
+#[tokio::test]
+async fn basic_usage() {
+    let mut stream = StreamNotifyClose::new(tokio_stream::iter(vec![0, 1]));
+
+    assert_eq!(stream.next().await, Some(Some(0)));
+    assert_eq!(stream.next().await, Some(Some(1)));
+    assert_eq!(stream.next().await, Some(None));
+    assert_eq!(stream.next().await, None);
+}

tokio-stream/tests/stream_panic.rs

@@ -1,5 +1,6 @@
 #![warn(rust_2018_idioms)]
 #![cfg(all(feature = "time", not(target_os = "wasi")))] // Wasi does not support panic recovery
+#![cfg(panic = "unwind")]
 
 use parking_lot::{const_mutex, Mutex};
 use std::error::Error;

tokio-stream/tests/stream_stream_map.rs

@@ -1,14 +1,17 @@
+use futures::stream::iter;
 use tokio_stream::{self as stream, pending, Stream, StreamExt, StreamMap};
 use tokio_test::{assert_ok, assert_pending, assert_ready, task};
 
+use std::future::{poll_fn, Future};
+use std::pin::{pin, Pin};
+use std::task::Poll;
+
 mod support {
     pub(crate) mod mpsc;
 }
 
 use support::mpsc;
 
-use std::pin::Pin;
-
 macro_rules! assert_ready_some {
     ($($t:tt)*) => {
         match assert_ready!($($t)*) {
@@ -325,63 +328,236 @@ fn one_ready_many_none() {
     }
 }
 
-#[cfg(not(target_os = "wasi"))]
-proptest::proptest! {
-    #[test]
-    fn fuzz_pending_complete_mix(kinds: Vec<bool>) {
-        use std::task::{Context, Poll};
-
-        struct DidPoll<T> {
-            did_poll: bool,
-            inner: T,
-        }
-
-        impl<T: Stream + Unpin> Stream for DidPoll<T> {
-            type Item = T::Item;
-
-            fn poll_next(mut self: Pin<&mut Self>, cx: &mut Context<'_>)
-                -> Poll<Option<T::Item>>
-            {
-                self.did_poll = true;
-                Pin::new(&mut self.inner).poll_next(cx)
-            }
-        }
-
-        for _ in 0..10 {
-            let mut map = task::spawn(StreamMap::new());
-            let mut expect = 0;
-
-            for (i, &is_empty) in kinds.iter().enumerate() {
-                let inner = if is_empty {
-                    pin_box(stream::empty::<()>())
-                } else {
-                    expect += 1;
-                    pin_box(stream::pending::<()>())
-                };
-
-                let stream = DidPoll {
-                    did_poll: false,
-                    inner,
-                };
-
-                map.insert(i, stream);
-            }
-
-            if expect == 0 {
-                assert_ready_none!(map.poll_next());
-            } else {
-                assert_pending!(map.poll_next());
-
-                assert_eq!(expect, map.values().count());
-
-                for stream in map.values() {
-                    assert!(stream.did_poll);
-                }
-            }
-        }
-    }
-}
-
 fn pin_box<T: Stream<Item = U> + 'static, U>(s: T) -> Pin<Box<dyn Stream<Item = U>>> {
     Box::pin(s)
 }
+
+type UsizeStream = Pin<Box<dyn Stream<Item = usize> + Send>>;
+
+#[tokio::test]
+async fn poll_next_many_zero() {
+    let mut stream_map: StreamMap<usize, UsizeStream> = StreamMap::new();
+
+    stream_map.insert(0, Box::pin(pending()) as UsizeStream);
+
+    let n = poll_fn(|cx| stream_map.poll_next_many(cx, &mut vec![], 0)).await;
+
+    assert_eq!(n, 0);
+}
+
+#[tokio::test]
+async fn poll_next_many_empty() {
+    let mut stream_map: StreamMap<usize, UsizeStream> = StreamMap::new();
+
+    let n = poll_fn(|cx| stream_map.poll_next_many(cx, &mut vec![], 1)).await;
+
+    assert_eq!(n, 0);
+}
+
+#[tokio::test]
+async fn poll_next_many_pending() {
+    let mut stream_map: StreamMap<usize, UsizeStream> = StreamMap::new();
+
+    stream_map.insert(0, Box::pin(pending()) as UsizeStream);
+
+    let mut is_pending = false;
+    poll_fn(|cx| {
+        let poll = stream_map.poll_next_many(cx, &mut vec![], 1);
+
+        is_pending = poll.is_pending();
+
+        Poll::Ready(())
+    })
+    .await;
+
+    assert!(is_pending);
+}
+
+#[tokio::test]
+async fn poll_next_many_not_enough() {
+    let mut stream_map: StreamMap<usize, UsizeStream> = StreamMap::new();
+
+    stream_map.insert(0, Box::pin(iter([0usize].into_iter())) as UsizeStream);
+    stream_map.insert(1, Box::pin(iter([1usize].into_iter())) as UsizeStream);
+
+    let mut buffer = vec![];
+    let n = poll_fn(|cx| stream_map.poll_next_many(cx, &mut buffer, 3)).await;
+
+    assert_eq!(n, 2);
+    assert_eq!(buffer.len(), 2);
+    assert!(buffer.contains(&(0, 0)));
+    assert!(buffer.contains(&(1, 1)));
+}
+
+#[tokio::test]
+async fn poll_next_many_enough() {
+    let mut stream_map: StreamMap<usize, UsizeStream> = StreamMap::new();
+
+    stream_map.insert(0, Box::pin(iter([0usize].into_iter())) as UsizeStream);
+    stream_map.insert(1, Box::pin(iter([1usize].into_iter())) as UsizeStream);
+
+    let mut buffer = vec![];
+    let n = poll_fn(|cx| stream_map.poll_next_many(cx, &mut buffer, 2)).await;
+
+    assert_eq!(n, 2);
+    assert_eq!(buffer.len(), 2);
+    assert!(buffer.contains(&(0, 0)));
+    assert!(buffer.contains(&(1, 1)));
+}
+
+#[tokio::test]
+async fn poll_next_many_correctly_loops_around() {
+    for _ in 0..10 {
+        let mut stream_map: StreamMap<usize, UsizeStream> = StreamMap::new();
+
+        stream_map.insert(0, Box::pin(iter([0usize].into_iter())) as UsizeStream);
+        stream_map.insert(1, Box::pin(iter([0usize, 1].into_iter())) as UsizeStream);
+        stream_map.insert(2, Box::pin(iter([0usize, 1, 2].into_iter())) as UsizeStream);
+
+        let mut buffer = vec![];
+
+        let n = poll_fn(|cx| stream_map.poll_next_many(cx, &mut buffer, 3)).await;
+        assert_eq!(n, 3);
+        assert_eq!(
+            std::mem::take(&mut buffer)
+                .into_iter()
+                .map(|(_, v)| v)
+                .collect::<Vec<_>>(),
+            vec![0, 0, 0]
+        );
+
+        let n = poll_fn(|cx| stream_map.poll_next_many(cx, &mut buffer, 2)).await;
+        assert_eq!(n, 2);
+        assert_eq!(
+            std::mem::take(&mut buffer)
+                .into_iter()
+                .map(|(_, v)| v)
+                .collect::<Vec<_>>(),
+            vec![1, 1]
+        );
+
+        let n = poll_fn(|cx| stream_map.poll_next_many(cx, &mut buffer, 1)).await;
+        assert_eq!(n, 1);
+        assert_eq!(
+            std::mem::take(&mut buffer)
+                .into_iter()
+                .map(|(_, v)| v)
+                .collect::<Vec<_>>(),
+            vec![2]
+        );
+    }
+}
+
+#[tokio::test]
+async fn next_many_zero() {
+    let mut stream_map: StreamMap<usize, UsizeStream> = StreamMap::new();
+
+    stream_map.insert(0, Box::pin(pending()) as UsizeStream);
+
+    let n = poll_fn(|cx| pin!(stream_map.next_many(&mut vec![], 0)).poll(cx)).await;
+
+    assert_eq!(n, 0);
+}
+
+#[tokio::test]
+async fn next_many_empty() {
+    let mut stream_map: StreamMap<usize, UsizeStream> = StreamMap::new();
+
+    let n = stream_map.next_many(&mut vec![], 1).await;
+
+    assert_eq!(n, 0);
+}
+
+#[tokio::test]
+async fn next_many_pending() {
+    let mut stream_map: StreamMap<usize, UsizeStream> = StreamMap::new();
+
+    stream_map.insert(0, Box::pin(pending()) as UsizeStream);
+
+    let mut is_pending = false;
+    poll_fn(|cx| {
+        let poll = pin!(stream_map.next_many(&mut vec![], 1)).poll(cx);
+
+        is_pending = poll.is_pending();
+
+        Poll::Ready(())
+    })
+    .await;
+
+    assert!(is_pending);
+}
+
+#[tokio::test]
+async fn next_many_not_enough() {
+    let mut stream_map: StreamMap<usize, UsizeStream> = StreamMap::new();
+
+    stream_map.insert(0, Box::pin(iter([0usize].into_iter())) as UsizeStream);
+    stream_map.insert(1, Box::pin(iter([1usize].into_iter())) as UsizeStream);
+
+    let mut buffer = vec![];
+    let n = poll_fn(|cx| pin!(stream_map.next_many(&mut buffer, 3)).poll(cx)).await;
+
+    assert_eq!(n, 2);
+    assert_eq!(buffer.len(), 2);
+    assert!(buffer.contains(&(0, 0)));
+    assert!(buffer.contains(&(1, 1)));
+}
+
+#[tokio::test]
+async fn next_many_enough() {
+    let mut stream_map: StreamMap<usize, UsizeStream> = StreamMap::new();
+
+    stream_map.insert(0, Box::pin(iter([0usize].into_iter())) as UsizeStream);
+    stream_map.insert(1, Box::pin(iter([1usize].into_iter())) as UsizeStream);
+
+    let mut buffer = vec![];
+    let n = poll_fn(|cx| pin!(stream_map.next_many(&mut buffer, 2)).poll(cx)).await;
+
+    assert_eq!(n, 2);
+    assert_eq!(buffer.len(), 2);
+    assert!(buffer.contains(&(0, 0)));
+    assert!(buffer.contains(&(1, 1)));
+}
+
+#[tokio::test]
+async fn next_many_correctly_loops_around() {
+    for _ in 0..10 {
+        let mut stream_map: StreamMap<usize, UsizeStream> = StreamMap::new();
+
+        stream_map.insert(0, Box::pin(iter([0usize].into_iter())) as UsizeStream);
+        stream_map.insert(1, Box::pin(iter([0usize, 1].into_iter())) as UsizeStream);
+        stream_map.insert(2, Box::pin(iter([0usize, 1, 2].into_iter())) as UsizeStream);
+
+        let mut buffer = vec![];
+
+        let n = poll_fn(|cx| pin!(stream_map.next_many(&mut buffer, 3)).poll(cx)).await;
+        assert_eq!(n, 3);
+        assert_eq!(
+            std::mem::take(&mut buffer)
+                .into_iter()
+                .map(|(_, v)| v)
+                .collect::<Vec<_>>(),
+            vec![0, 0, 0]
+        );
+
+        let n = poll_fn(|cx| pin!(stream_map.next_many(&mut buffer, 2)).poll(cx)).await;
+        assert_eq!(n, 2);
+        assert_eq!(
+            std::mem::take(&mut buffer)
+                .into_iter()
+                .map(|(_, v)| v)
+                .collect::<Vec<_>>(),
+            vec![1, 1]
+        );
+
+        let n = poll_fn(|cx| pin!(stream_map.next_many(&mut buffer, 1)).poll(cx)).await;
+        assert_eq!(n, 1);
+        assert_eq!(
+            std::mem::take(&mut buffer)
+                .into_iter()
+                .map(|(_, v)| v)
+                .collect::<Vec<_>>(),
+            vec![2]
+        );
+    }
+}

tokio-stream/tests/stream_timeout.rs

@@ -1,7 +1,7 @@
 #![cfg(all(feature = "time", feature = "sync", feature = "io-util"))]
 
 use tokio::time::{self, sleep, Duration};
-use tokio_stream::{self, StreamExt};
+use tokio_stream::StreamExt;
 use tokio_test::*;
 
 use futures::stream;

tokio-stream/tests/watch.rs

@@ -3,9 +3,11 @@
 use tokio::sync::watch;
 use tokio_stream::wrappers::WatchStream;
 use tokio_stream::StreamExt;
+use tokio_test::assert_pending;
+use tokio_test::task::spawn;
 
 #[tokio::test]
-async fn message_not_twice() {
+async fn watch_stream_message_not_twice() {
     let (tx, rx) = watch::channel("hello");
 
     let mut counter = 0;
@@ -27,3 +29,29 @@ async fn message_not_twice() {
     drop(tx);
     task.await.unwrap();
 }
+
+#[tokio::test]
+async fn watch_stream_from_rx() {
+    let (tx, rx) = watch::channel("hello");
+
+    let mut stream = WatchStream::from(rx);
+
+    assert_eq!(stream.next().await.unwrap(), "hello");
+
+    tx.send("bye").unwrap();
+
+    assert_eq!(stream.next().await.unwrap(), "bye");
+}
+
+#[tokio::test]
+async fn watch_stream_from_changes() {
+    let (tx, rx) = watch::channel("hello");
+
+    let mut stream = WatchStream::from_changes(rx);
+
+    assert_pending!(spawn(&mut stream).poll_next());
+
+    tx.send("bye").unwrap();
+
+    assert_eq!(stream.next().await.unwrap(), "bye");
+}

tokio-test/CHANGELOG.md

@@ -1,3 +1,27 @@
+# 0.4.4 (March 14, 2024)
+
+- task: mark `Spawn` as `#[must_use]` ([#6371])
+- test: increase MSRV to 1.63 ([#6126])
+- test: update category slug ([#5953])
+
+[#5953]: https://github.com/tokio-rs/tokio/pull/5953
+[#6126]: https://github.com/tokio-rs/tokio/pull/6126
+[#6371]: https://github.com/tokio-rs/tokio/pull/6371
+
+# 0.4.3 (August 23, 2023)
+
+- deps: fix minimum required version of `async-stream` ([#5347])
+- deps: fix minimum required version of `tokio-stream` ([#4376])
+- docs: improve `tokio_test::task` docs ([#5132])
+- io: fetch actions from mock handle before write ([#5814])
+- io: fix wait operation on mock ([#5554])
+
+[#4376]: https://github.com/tokio-rs/tokio/pull/4376
+[#5132]: https://github.com/tokio-rs/tokio/pull/5132
+[#5347]: https://github.com/tokio-rs/tokio/pull/5347
+[#5554]: https://github.com/tokio-rs/tokio/pull/5554
+[#5814]: https://github.com/tokio-rs/tokio/pull/5814
+
 # 0.4.2 (May 14, 2021)
 
 - test: add `assert_elapsed!` macro ([#3728])

tokio-test/Cargo.toml

@@ -4,9 +4,9 @@ name = "tokio-test"
 # - Remove path dependencies
 # - Update CHANGELOG.md.
 # - Create "tokio-test-0.4.x" git tag.
-version = "0.4.2"
-edition = "2018"
-rust-version = "1.49"
+version = "0.4.4"
+edition = "2021"
+rust-version = "1.63"
 authors = ["Tokio Contributors <[email protected]>"]
 license = "MIT"
 repository = "https://github.com/tokio-rs/tokio"
@@ -14,7 +14,7 @@ homepage = "https://tokio.rs"
 description = """
 Testing utilities for Tokio- and futures-based code
 """
-categories = ["asynchronous", "testing"]
+categories = ["asynchronous", "development-tools::testing"]
 
 [dependencies]
 tokio = { version = "1.2.0", path = "../tokio", features = ["rt", "sync", "time", "test-util"] }

tokio-test/LICENSE

@@ -1,25 +1,21 @@
-Copyright (c) 2022 Tokio Contributors
+MIT License
 
-Permission is hereby granted, free of charge, to any
-person obtaining a copy of this software and associated
-documentation files (the "Software"), to deal in the
-Software without restriction, including without
-limitation the rights to use, copy, modify, merge,
-publish, distribute, sublicense, and/or sell copies of
-the Software, and to permit persons to whom the Software
-is furnished to do so, subject to the following
-conditions:
+Copyright (c) Tokio Contributors
 
-The above copyright notice and this permission notice
-shall be included in all copies or substantial portions
-of the Software.
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
 
-THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF
-ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED
-TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
-PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT
-SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
-CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
-OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR
-IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
-DEALINGS IN THE SOFTWARE.
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

tokio-test/src/io.rs

@@ -74,7 +74,7 @@ struct Inner {
 }
 
 impl Builder {
-    /// Return a new, empty `Builder.
+    /// Return a new, empty `Builder`.
     pub fn new() -> Self {
         Self::default()
     }
@@ -310,6 +310,8 @@ impl Inner {
 
                         if now < until {
                             break;
+                        } else {
+                            self.waiting = None;
                         }
                     } else {
                         self.waiting = Some(Instant::now() + *dur);
@@ -407,6 +409,20 @@ impl AsyncWrite for Mock {
             // If a sleep is set, it has already fired
             self.inner.sleep = None;
 
+            if self.inner.actions.is_empty() {
+                match self.inner.poll_action(cx) {
+                    Poll::Pending => {
+                        // do not propagate pending
+                    }
+                    Poll::Ready(Some(action)) => {
+                        self.inner.actions.push_back(action);
+                    }
+                    Poll::Ready(None) => {
+                        panic!("unexpected write");
+                    }
+                }
+            }
+
             match self.inner.write(buf) {
                 Err(ref e) if e.kind() == io::ErrorKind::WouldBlock => {
                     if let Some(rem) = self.inner.remaining_wait() {
@@ -462,7 +478,7 @@ impl Drop for Mock {
             Action::Read(data) => assert!(data.is_empty(), "There is still data left to read."),
             Action::Write(data) => assert!(data.is_empty(), "There is still data left to write."),
             _ => (),
-        })
+        });
     }
 }
 /*

tokio-test/src/lib.rs

@@ -1,3 +1,4 @@
+#![allow(unknown_lints, unexpected_cfgs)]
 #![warn(
     missing_debug_implementations,
     missing_docs,
@@ -12,6 +13,7 @@
 //! Tokio and Futures based testing utilities
 
 pub mod io;
+pub mod stream_mock;
 
 mod macros;
 pub mod task;

tokio-test/src/macros.rs

@@ -22,17 +22,17 @@
 #[macro_export]
 macro_rules! assert_ready {
     ($e:expr) => {{
-        use core::task::Poll::*;
+        use core::task::Poll;
         match $e {
-            Ready(v) => v,
-            Pending => panic!("pending"),
+            Poll::Ready(v) => v,
+            Poll::Pending => panic!("pending"),
         }
     }};
     ($e:expr, $($msg:tt)+) => {{
-        use core::task::Poll::*;
+        use core::task::Poll;
         match $e {
-            Ready(v) => v,
-            Pending => {
+            Poll::Ready(v) => v,
+            Poll::Pending => {
                 panic!("pending; {}", format_args!($($msg)+))
             }
         }
@@ -127,17 +127,17 @@ macro_rules! assert_ready_err {
 #[macro_export]
 macro_rules! assert_pending {
     ($e:expr) => {{
-        use core::task::Poll::*;
+        use core::task::Poll;
         match $e {
-            Pending => {}
-            Ready(v) => panic!("ready; value = {:?}", v),
+            Poll::Pending => {}
+            Poll::Ready(v) => panic!("ready; value = {:?}", v),
         }
     }};
     ($e:expr, $($msg:tt)+) => {{
-        use core::task::Poll::*;
+        use core::task::Poll;
         match $e {
-            Pending => {}
-            Ready(v) => {
+            Poll::Pending => {}
+            Poll::Ready(v) => {
                 panic!("ready; value = {:?}; {}", v, format_args!($($msg)+))
             }
         }

tokio-test/src/stream_mock.rs

@@ -0,0 +1,168 @@
+#![cfg(not(loom))]
+
+//! A mock stream implementing [`Stream`].
+//!
+//! # Overview
+//! This crate provides a `StreamMock` that can be used to test code that interacts with streams.
+//! It allows you to mock the behavior of a stream and control the items it yields and the waiting
+//! intervals between items.
+//!
+//! # Usage
+//! To use the `StreamMock`, you need to create a builder using [`StreamMockBuilder`]. The builder
+//! allows you to enqueue actions such as returning items or waiting for a certain duration.
+//!
+//! # Example
+//! ```rust
+//!
+//! use futures_util::StreamExt;
+//! use std::time::Duration;
+//! use tokio_test::stream_mock::StreamMockBuilder;
+//!
+//! async fn test_stream_mock_wait() {
+//!     let mut stream_mock = StreamMockBuilder::new()
+//!         .next(1)
+//!         .wait(Duration::from_millis(300))
+//!         .next(2)
+//!         .build();
+//!
+//!     assert_eq!(stream_mock.next().await, Some(1));
+//!     let start = std::time::Instant::now();
+//!     assert_eq!(stream_mock.next().await, Some(2));
+//!     let elapsed = start.elapsed();
+//!     assert!(elapsed >= Duration::from_millis(300));
+//!     assert_eq!(stream_mock.next().await, None);
+//! }
+//! ```
+
+use std::collections::VecDeque;
+use std::pin::Pin;
+use std::task::Poll;
+use std::time::Duration;
+
+use futures_core::{ready, Stream};
+use std::future::Future;
+use tokio::time::{sleep_until, Instant, Sleep};
+
+#[derive(Debug, Clone)]
+enum Action<T: Unpin> {
+    Next(T),
+    Wait(Duration),
+}
+
+/// A builder for [`StreamMock`]
+#[derive(Debug, Clone)]
+pub struct StreamMockBuilder<T: Unpin> {
+    actions: VecDeque<Action<T>>,
+}
+
+impl<T: Unpin> StreamMockBuilder<T> {
+    /// Create a new empty [`StreamMockBuilder`]
+    pub fn new() -> Self {
+        StreamMockBuilder::default()
+    }
+
+    /// Queue an item to be returned by the stream
+    pub fn next(mut self, value: T) -> Self {
+        self.actions.push_back(Action::Next(value));
+        self
+    }
+
+    // Queue an item to be consumed by the sink,
+    // commented out until Sink is implemented.
+    //
+    // pub fn consume(mut self, value: T) -> Self {
+    //    self.actions.push_back(Action::Consume(value));
+    //    self
+    // }
+
+    /// Queue the stream to wait for a duration
+    pub fn wait(mut self, duration: Duration) -> Self {
+        self.actions.push_back(Action::Wait(duration));
+        self
+    }
+
+    /// Build the [`StreamMock`]
+    pub fn build(self) -> StreamMock<T> {
+        StreamMock {
+            actions: self.actions,
+            sleep: None,
+        }
+    }
+}
+
+impl<T: Unpin> Default for StreamMockBuilder<T> {
+    fn default() -> Self {
+        StreamMockBuilder {
+            actions: VecDeque::new(),
+        }
+    }
+}
+
+/// A mock stream implementing [`Stream`]
+///
+/// See [`StreamMockBuilder`] for more information.
+#[derive(Debug)]
+pub struct StreamMock<T: Unpin> {
+    actions: VecDeque<Action<T>>,
+    sleep: Option<Pin<Box<Sleep>>>,
+}
+
+impl<T: Unpin> StreamMock<T> {
+    fn next_action(&mut self) -> Option<Action<T>> {
+        self.actions.pop_front()
+    }
+}
+
+impl<T: Unpin> Stream for StreamMock<T> {
+    type Item = T;
+
+    fn poll_next(
+        mut self: std::pin::Pin<&mut Self>,
+        cx: &mut std::task::Context<'_>,
+    ) -> std::task::Poll<Option<Self::Item>> {
+        // Try polling the sleep future first
+        if let Some(ref mut sleep) = self.sleep {
+            ready!(Pin::new(sleep).poll(cx));
+            // Since we're ready, discard the sleep future
+            self.sleep.take();
+        }
+
+        match self.next_action() {
+            Some(action) => match action {
+                Action::Next(item) => Poll::Ready(Some(item)),
+                Action::Wait(duration) => {
+                    // Set up a sleep future and schedule this future to be polled again for it.
+                    self.sleep = Some(Box::pin(sleep_until(Instant::now() + duration)));
+                    cx.waker().wake_by_ref();
+
+                    Poll::Pending
+                }
+            },
+            None => Poll::Ready(None),
+        }
+    }
+}
+
+impl<T: Unpin> Drop for StreamMock<T> {
+    fn drop(&mut self) {
+        // Avoid double panicking to make debugging easier.
+        if std::thread::panicking() {
+            return;
+        }
+
+        let undropped_count = self
+            .actions
+            .iter()
+            .filter(|action| match action {
+                Action::Next(_) => true,
+                Action::Wait(_) => false,
+            })
+            .count();
+
+        assert!(
+            undropped_count == 0,
+            "StreamMock was dropped before all actions were consumed, {} actions were not consumed",
+            undropped_count
+        );
+    }
+}