rt: cleanup and simplify scheduler (scheduler v2.5) (#2273)

A refactor of the scheduler internals focusing on simplifying and
reducing unsafety. There are no fundamental logic changes.

* The state transitions of the core task component are refined and
reduced.
* `basic_scheduler` has most unsafety removed.
* `local_set` has most unsafety removed.
* `threaded_scheduler` limits most unsafety to its queue implementation.

ci/azure-check-features.yml

@@ -6,7 +6,7 @@ jobs:
       Linux:
         vmImage: ubuntu-16.04
       MacOS:
-        vmImage: macOS-10.13
+        vmImage: macos-latest
       Windows:
         vmImage: vs2017-win2016
   pool:

ci/azure-install-rust.yml

@@ -2,6 +2,13 @@ steps:
   # Linux and macOS.
   - script: |
       set -e
+
+      if [ "$RUSTUP_TOOLCHAIN" == "nightly" ]; then
+        echo "++ getting latest miri version"
+        export RUSTUP_TOOLCHAIN="nightly-$(curl -s https://rust-lang.github.io/rustup-components-history/x86_64-unknown-linux-gnu/miri)"
+        echo "$RUSTUP_TOOLCHAIN"
+      fi
+
       curl https://sh.rustup.rs -sSf | sh -s -- -y --profile minimal --default-toolchain none
       export PATH=$PATH:$HOME/.cargo/bin
       rustup toolchain install $RUSTUP_TOOLCHAIN

ci/azure-loom.yml

@@ -1,6 +1,18 @@
 jobs:
 - job: ${{ parameters.name }}
   displayName: Loom tests
+  strategy:
+    matrix:
+      rest:
+        scope: --skip loom_pool
+      pool_group_a:
+        scope: loom_pool::group_a
+      pool_group_b:
+        scope: loom_pool::group_b
+      pool_group_c:
+        scope: loom_pool::group_c
+      pool_group_d:
+        scope: loom_pool::group_d
   pool:
     vmImage: ubuntu-16.04
 
@@ -9,10 +21,9 @@ jobs:
     parameters:
       rust_version: ${{ parameters.rust }}
 
-  - ${{ each crate in parameters.crates }}:
-    - script: RUSTFLAGS="--cfg loom" cargo test --lib --release --features "full" -- --test-threads=1 --nocapture
-      env:
-        LOOM_MAX_PREEMPTIONS: 1
-        CI: 'True'
-      displayName: test ${{ crate }}
-      workingDirectory: $(Build.SourcesDirectory)/${{ crate }}
+  - script: RUSTFLAGS="--cfg loom" cargo test --lib --release --features "full" -- --nocapture $(scope)
+    env:
+      LOOM_MAX_PREEMPTIONS: 2
+      CI: 'True'
+    displayName: $(scope)
+    workingDirectory: $(Build.SourcesDirectory)/tokio

ci/azure-miri.yml

@@ -0,0 +1,23 @@
+jobs:
+- job: ${{ parameters.name }}
+  displayName: Miri
+  pool:
+    vmImage: ubuntu-16.04
+
+  steps:
+  - template: azure-install-rust.yml
+    parameters:
+      rust_version: nightly
+
+  - script: |
+      rustup component add miri
+      cargo miri setup
+      rm -rf $(Build.SourcesDirectory)/tokio/tests
+    displayName: Install miri
+
+  # TODO: enable all tests once they pass
+  - script: cargo miri test --features rt-core,rt-threaded,rt-util,sync -- -- task
+    env:
+      CI: 'True'
+    displayName: cargo miri test
+    workingDirectory: $(Build.SourcesDirectory)/tokio

ci/azure-test-integration.yml

@@ -6,7 +6,7 @@ jobs:
       Linux:
         vmImage: ubuntu-16.04
       MacOS:
-        vmImage: macOS-10.13
+        vmImage: macos-latest
       Windows:
         vmImage: vs2017-win2016
   pool:

ci/azure-test-stable.yml

@@ -8,7 +8,7 @@ jobs:
 
       ${{ if parameters.cross }}:
         MacOS:
-          vmImage: macOS-10.13
+          vmImage: macos-latest
         Windows:
           vmImage: vs2017-win2016
   pool: