Uses the infrastructure added by #2828 to enable switching
`TcpListener::accept` to use `&self`.
This also switches `poll_accept` to use `&self`. While doing introduces
a hazard, `poll_*` style functions are considered low-level. Most users
will use the `async fn` variants which are more misuse-resistant.
TcpListener::incoming() is temporarily removed as it has the same
problem as `TcpSocket::by_ref()` and will be implemented later.
This refactors I/O registration in a few ways:
- Cleans up the cached readiness in `PollEvented`. This cache used to
be helpful when readiness was a linked list of `*mut Node`s in
`Registration`. Previous refactors have turned `Registration` into just
an `AtomicUsize` holding the current readiness, so the cache is just
extra work and complexity. Gone.
- Polling the `Registration` for readiness now gives a `ReadyEvent`,
which includes the driver tick. This event must be passed back into
`clear_readiness`, so that the readiness is only cleared from `Registration`
if the tick hasn't changed. Previously, it was possible to clear the
readiness even though another thread had *just* polled the driver and
found the socket ready again.
- Registration now also contains an `async fn readiness`, which stores
wakers in an instrusive linked list. This allows an unbounded number
of tasks to register for readiness (previously, only 1 per direction (read
and write)). By using the intrusive linked list, there is no concern of
leaking the storage of the wakers, since they are stored inside the `async fn`
and released when the future is dropped.
- Registration retains a `poll_readiness(Direction)` method, to support
`AsyncRead` and `AsyncWrite`. They aren't able to use `async fn`s, and
so there are 2 reserved slots for those methods.
- IO types where it makes sense to have multiple tasks waiting on them
now take advantage of this new `async fn readiness`, such as `UdpSocket`
and `UnixDatagram`.
Additionally, this makes the `io-driver` "feature" internal-only (no longer
documented, not part of public API), and adds a second internal-only
feature, `io-readiness`, to group together linked list part of registration
that is only used by some of the IO types.
After a bit of discussion, changing stream-based transports (like
`TcpStream`) to have `async fn read(&self)` is punted, since that
is likely too easy of a footgun to activate.
Refs: #2779, #2728
JoinHandle of threads created by the pool are now tracked and properly joined at
shutdown. If the thread does not return within the timeout, then it's not joined and
left to the OS for cleanup.
Also, break a cycle between wakers held by the timer and the runtime.
Fixes#2641, #2535
Previously, dropping the Write handle would issue a `shutdown(Both)`. However,
shutting down the read half is not portable and not the correct action to take.
This changes the behavior of OwnedWriteHalf to only perform a `shutdown(Write)`
on drop.
The new queue uses `u8` to track offsets. Cursors are expected to wrap.
An operation was performed with `+` instead of `wrapping_add`. This was
not _obviously_ issue before as it is difficult to wrap a `usize` on
64bit platforms, but wrapping a `u8` is trivial.
The fix is to use `wrapping_add` instead of `+`. A new test is added
that catches the issue.
Fixes#2361
The work-stealing scheduler includes an optimization where each worker
includes a single slot to store the **last** scheduled task. Tasks in
scheduler's LIFO slot are executed next. This speeds up and reduces
latency with message passing patterns.
Previously, this optimization was susceptible to starving other tasks in
certain cases. If two tasks ping-ping between each other without ever
yielding, the worker would never execute other tasks.
An early PR (#2160) introduced a form of pre-emption. Each task is
allocated a per-poll operation budget. Tokio resources will return ready
until the budget is depleted, at which point, Tokio resources will
always return `Pending`.
This patch leverages the operation budget to limit the LIFO scheduler
optimization. When executing tasks from the LIFO slot, the budget is
**not** reset. Once the budget goes to zero, the task in the LIFO slot
is pushed to the back of the queue.
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.
Previously, if an IO event was received during the runtime shutdown
process, it was possible to enter a deadlock. This was due to the
scheduler shutdown logic not expecting tasks to get scheduled once the
worker was in the shutdown process.
This patch fixes the deadlock by checking the queues for new tasks after
each call to park. If a new task is received, it is forcefully shutdown.
Fixes#2061
Storing a `Runtime` value in a thread-local resulted in a panic due to
the inability to access the parker.
This fixes the bug by skipping parking if it fails. In general, there
isn't much that we can do besides not parking.
Fixes#593
Nested spawn_blocking calls would result in a panic due to the necessary
context not being setup. This patch sets the blocking pool context from
within a blocking pool.
Fixes#1982
The "global executor" thread-local is to track where to spawn new tasks,
**not** which scheduler is active on the current thread. This fixes a
bug with scheduling tasks on the basic_scheduler by tracking the
currently active basic_scheduler with a dedicated thread-local variable.
Fixes: #1851
## Motivation
In earlier versions of `tokio`, the `current_thread::Runtime` type could
be used to run `!Send` futures. However, PR #1716 merged the
current-thread and threadpool runtimes into a single type, which can no
longer run `!Send` futures. There is still a need in some cases to
support futures that don't implement `Send`, and the `tokio-compat`
crate requires this in order to provide APIs that existed in `tokio`
0.1.
## Solution
This branch implements the API described by @carllerche in
https://github.com/tokio-rs/tokio/pull/1716#issuecomment-549496309. It
adds a new `LocalSet` type and `spawn_local` function to `tokio::task`.
The `LocalSet` type is used to group together a set of tasks which must
run on the same thread and don't implement `Send`. These are available
when a new "rt-util" feature flag is enabled.
Currently, the local task set is run by passing it a reference to a
`Runtime` and a future to `block_on`. In the future, we may also want
to investigate allowing spawned futures to construct their own local
task sets, which would be executed on the worker that the future is
executing on.
In order to implement the new API, I've made some internal changes to
the `task` module and `Schedule` trait to support scheduling both `Send`
and `!Send` futures.
Signed-off-by: Eliza Weisman <[email protected]>
Changes the set of `default` feature flags to `[]`. By default, only
core traits are included without specifying feature flags. This makes it
easier for users to pick the components they need.
For convenience, a `full` feature flag is included that includes all
components.
Tests are configured to require the `full` feature. Testing individual
feature flags will need to be moved to a separate crate.
Closes#1791
* runtime: cleanup and add config options
This patch finishes the cleanup as part of the transition to Tokio 0.2.
A number of changes were made to take advantage of having all Tokio
types in a single crate. Also, fixes using Tokio types from
`spawn_blocking`.
* Many threads, one resource driver
Previously, in the threaded scheduler, a resource driver (mio::Poll /
timer combo) was created per thread. This was more or less fine, except
it required balancing across the available drivers. When using a
resource driver from **outside** of the thread pool, balancing is
tricky. The change was original done to avoid having a dedicated driver
thread.
Now, instead of creating many resource drivers, a single resource driver
is used. Each scheduler thread will attempt to "lock" the resource
driver before parking on it. If the resource driver is already locked,
the thread uses a condition variable to park. Contention should remain
low as, under load, the scheduler avoids using the drivers.
* Add configuration options to enable I/O / time
New configuration options are added to `runtime::Builder` to allow
enabling I/O and time drivers on a runtime instance basis. This is
useful when wanting to create lightweight runtime instances to execute
compute only tasks.
* Bug fixes
The condition variable parker is updated to the same algorithm used in
`std`. This is motivated by some potential deadlock cases discovered by
`loom`.
The basic scheduler is fixed to fairly schedule tasks. `push_front` was
accidentally used instead of `push_back`.
I/O, time, and spawning now work from within `spawn_blocking` closures.
* Misc cleanup
The threaded scheduler is no longer generic over `P :Park`. Instead, it
is hard coded to a specific parker. Tests, including loom tests, are
updated to use `Runtime` directly. This provides greater coverage.
The `blocking` module is moved back into `runtime` as all usage is
within `runtime` itself.
It no longer supports executing !Send futures. The use case for
It is wanting a “light” runtime. There will be “local” task execution
using a different strategy coming later.
This patch also renames `thread_pool` -> `threaded_scheduler`, but
only in public APIs for now.
In an effort to reach API stability, the `tokio` crate is shedding its
_public_ dependencies on crates that are either a) do not provide a
stable (1.0+) release with longevity guarantees or b) match the `tokio`
release cadence. Of course, implementing `std` traits fits the
requirements.
The on exception, for now, is the `Stream` trait found in `futures_core`.
It is expected that this trait will not change much and be moved into `std.
Since Tokio is not yet going reaching 1.0, I feel that it is acceptable to maintain
a dependency on this trait given how foundational it is.
Since the `Stream` implementation is optional, types that are logically
streams provide `async fn next_*` functions to obtain the next value.
Avoiding the `next()` name prevents fn conflicts with `StreamExt::next()`.
Additionally, some misc cleanup is also done:
- `tokio::io::io` -> `tokio::io::util`.
- `delay` -> `delay_until`.
- `Timeout::new` -> `timeout(...)`.
- `signal::ctrl_c()` returns a future instead of a stream.
- `{tcp,unix}::Incoming` is removed (due to lack of `Stream` trait).
- `time::Throttle` is removed (due to lack of `Stream` trait).
- Fix: `mpsc::UnboundedSender::send(&self)` (no more conflict with `Sink` fns).
This patch started as an effort to make `time::Timer` private. However, in an
effort to get the build compiling again, more and more changes were made. This
probably should have been broken up, but here we are. I will attempt to
summarize the changes here.
* Feature flags are reorganized to make clearer. `net-driver` becomes
`io-driver`. `rt-current-thread` becomes `rt-core`.
* The `Runtime` can be created without any executor. This replaces `enter`. It
also allows creating I/O / time drivers that are standalone.
* `tokio::timer` is renamed to `tokio::time`. This brings it in line with `std`.
* `tokio::timer::Timer` is renamed to `Driver` and made private.
* The `clock` module is removed. Instead, an `Instant` type is provided. This
type defaults to calling `std::time::Instant`. A `test-util` feature flag can
be used to enable hooking into time.
* The `blocking` module is moved to the top level and is cleaned up.
* The `task` module is moved to the top level.
* The thread-pool's in-place blocking implementation is cleaned up.
* `runtime::Spawner` is renamed to `runtime::Handle` and can be used to "enter"
a runtime context.
Fixes a bug in the thread-pool executor related to shutdown
concurrent with a task that is self-notifying. A `loom` test is
added to validate the fix.
Additionally, in anticipation of the `thread_pool` module being
switched to private, tests are updated to use `Runtime` directly
instead of `thread_pool`. Those tests that cannot be updated
are switched to unit tests.
Carl Lerche