rt: yield_now defers task until after driver poll #5223
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Previously, calling `task::yield_now().await` would yield the current task to the scheduler, but the scheduler would poll it again before polling the resource drivers. This behavior can result in starving the resource drivers. This patch creates a queue tracking yielded tasks. The scheduler notifies those tasks **after** polling the resource drivers.
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This would be amazing when merged! |
Darksonn
reviewed
Nov 23, 2022
Darksonn
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Ok, this PR should be ready for review. I will fix CI errors as they show up. |
…nto tweak-yield-now
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Ok, it seems like the multi-threaded test is still not correct. It is proving quite challenging to test it reliably with the multi-threaded work stealing. |
Darksonn
reviewed
Nov 25, 2022
tokio/tests/rt_common.rs
Outdated
| cnt += 1; | ||
| } | ||
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| assert!(cnt < 3, "actual={}", cnt); |
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Shouldn't this assertion complete after one iteration?
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False positives and all that are possible...
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I"m also seeing cases where the OS appears to delay the I/O notification. I don't think there is any reliable way to test this here. I added a loom test, though.
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Ah, it looks like the hang is on windows. I will investigate that next. |
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The windows fix was simple. |
Darksonn
approved these changes
Nov 30, 2022
carllerche
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Dec 1, 2022
PR #5223 changed the behavior of `yield_now()` to store yielded tasks and notify them *after* polling the resource drivers. This PR fixes a couple of bugs with this new behavior when combined with `block_in_place()`. First, we need to avoid freeing the deferred task queue when exiting a runtime if it is *not* the root runtime. Because `block_in_place()` allows a user to start a new runtime from within an existing task, this check is necessary. Second, when a worker core is stolen from a thread during a `block_in_place()` call, we need to ensure that deferred tasks are notified anyway.
carllerche
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Dec 2, 2022
PR #5223 changed the behavior of `yield_now()` to store yielded tasks and notify them *after* polling the resource drivers. This PR fixes a couple of bugs with this new behavior when combined with `block_in_place()`. First, we need to avoid freeing the deferred task queue when exiting a runtime if it is *not* the root runtime. Because `block_in_place()` allows a user to start a new runtime from within an existing task, this check is necessary. Second, when a worker core is stolen from a thread during a `block_in_place()` call, we need to ensure that deferred tasks are notified anyway.
carllerche
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Dec 5, 2022
- net: fix Windows named pipe connect ([#5208]) - io: support vectored writes for `ChildStdin` ([#5216]) - io: fix `async fn ready()` false positive for OS-specific events ([#5231]) ### Changed - runtime: `yield_now` defers task until after driver poll ([#5223]) - runtime: reduce amount of codegen needed per spawned task ([#5213]) - windows: replace `winapi` dependency with `windows-sys` ([#5204]) [#5208]: #5208 [#5216]: #5216 [#5213]: #5213 [#5204]: #5204 [#5223]: #5223 [#5231]: #5231
carllerche
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Dec 5, 2022
### Fixed - net: fix Windows named pipe connect ([#5208]) - io: support vectored writes for `ChildStdin` ([#5216]) - io: fix `async fn ready()` false positive for OS-specific events ([#5231]) ### Changed - runtime: `yield_now` defers task until after driver poll ([#5223]) - runtime: reduce amount of codegen needed per spawned task ([#5213]) - windows: replace `winapi` dependency with `windows-sys` ([#5204]) [#5208]: #5208 [#5216]: #5216 [#5213]: #5213 [#5204]: #5204 [#5223]: #5223 [#5231]: #5231
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Dec 23, 2022
This PR contains the following updates: | Package | Type | Update | Change | |---|---|---|---| | [tokio](https://tokio.rs) ([source](https://github.com/tokio-rs/tokio)) | dependencies | minor | `1.22.0` -> `1.23.0` | | [tokio](https://tokio.rs) ([source](https://github.com/tokio-rs/tokio)) | dev-dependencies | minor | `1.22.0` -> `1.23.0` | --- ### Release Notes <details> <summary>tokio-rs/tokio</summary> ### [`v1.23.0`](https://github.com/tokio-rs/tokio/releases/tag/tokio-1.23.0): Tokio v1.23.0 [Compare Source](tokio-rs/tokio@tokio-1.22.0...tokio-1.23.0) ##### Fixed - net: fix Windows named pipe connect ([#​5208]) - io: support vectored writes for `ChildStdin` ([#​5216]) - io: fix `async fn ready()` false positive for OS-specific events ([#​5231]) ##### Changed - runtime: `yield_now` defers task until after driver poll ([#​5223]) - runtime: reduce amount of codegen needed per spawned task ([#​5213]) - windows: replace `winapi` dependency with `windows-sys` ([#​5204]) [#​5208]: tokio-rs/tokio#5208 [#​5216]: tokio-rs/tokio#5216 [#​5213]: tokio-rs/tokio#5213 [#​5204]: tokio-rs/tokio#5204 [#​5223]: tokio-rs/tokio#5223 [#​5231]: tokio-rs/tokio#5231 </details> --- ### Configuration 📅 **Schedule**: Branch creation - At any time (no schedule defined), Automerge - At any time (no schedule defined). 🚦 **Automerge**: Disabled by config. Please merge this manually once you are satisfied. ♻ **Rebasing**: Whenever PR becomes conflicted, or you tick the rebase/retry checkbox. 🔕 **Ignore**: Close this PR and you won't be reminded about these updates again. --- - [ ] <!-- rebase-check -->If you want to rebase/retry this PR, check this box --- This PR has been generated by [Renovate Bot](https://github.com/renovatebot/renovate). <!--renovate-debug:eyJjcmVhdGVkSW5WZXIiOiIzNC43MC4wIiwidXBkYXRlZEluVmVyIjoiMzQuNzAuMCJ9--> Co-authored-by: cabr2-bot <cabr2.help@gmail.com> Reviewed-on: https://codeberg.org/Calciumdibromid/CaBr2/pulls/1687 Reviewed-by: crapStone <crapstone@noreply.codeberg.org> Co-authored-by: Calciumdibromid Bot <cabr2_bot@noreply.codeberg.org> Co-committed-by: Calciumdibromid Bot <cabr2_bot@noreply.codeberg.org>
hds
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Feb 16, 2024
Part of the testing performed in the `console-subscriber` integration tests is detecting self wakes. This relied upon the `yield_now()` from Tokio. However, the behavior of this function was changed in tokio-rs/tokio#5223 and since Tokio 1.23 the wake doesn't occur in the task that `yield_now()` is called from. This breaks the test when using a newer version of Tokio. This change replaces the use of `yield_now()` with a custom `self_wake()` function that returns a future which does perform a self wake (wakes the task from within itself before returning `Poll::Pending`). The same custom `self_wake()` is also included in the `app` example so that it shows self wakes correctly.
hds
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Feb 16, 2024
Part of the testing performed in the `console-subscriber` integration tests is detecting self wakes. This relied upon the `yield_now()` from Tokio. However, the behavior of this function was changed in tokio-rs/tokio#5223 and since Tokio 1.23 the wake doesn't occur in the task that `yield_now()` is called from. This breaks the test when using a newer version of Tokio. This change replaces the use of `yield_now()` with a custom `self_wake()` function that returns a future which does perform a self wake (wakes the task from within itself before returning `Poll::Pending`). The same custom `self_wake()` is also included in the `app` example so that it shows self wakes correctly. Tokio has been updated to 1.28.2 in the lock file (the last with compatible MSRV) so that this fix is tested. Ref #512
hds
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Mar 8, 2024
Part of the testing performed in the `console-subscriber` integration tests is detecting self wakes. This relied upon the `yield_now()` from Tokio. However, the behavior of this function was changed in tokio-rs/tokio#5223 and since Tokio 1.23 the wake doesn't occur in the task that `yield_now()` is called from. This breaks the test when using a newer version of Tokio. This change replaces the use of `yield_now()` with a custom `self_wake()` function that returns a future which does perform a self wake (wakes the task from within itself before returning `Poll::Pending`). The same custom `self_wake()` is also included in the `app` example so that it shows self wakes correctly. Tokio has been updated to 1.28.2 in the lock file (the last with compatible MSRV) so that this fix is tested. Ref #512
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Previously, calling
task::yield_now().awaitwould yield the current task to the scheduler, but the scheduler would poll it again before polling the resource drivers. This behavior can result in starving the resource drivers.This patch creates a queue tracking yielded tasks. The scheduler notifies those tasks after polling the resource drivers.