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rt: yield_now defers task until after driver poll #5223

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merged 15 commits into from Nov 30, 2022
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@carllerche carllerche commented Nov 22, 2022

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.

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.
@github-actions github-actions bot added the R-loom Run loom tests on this PR label Nov 22, 2022
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luben commented Nov 22, 2022

This would be amazing when merged!

@Darksonn Darksonn added A-tokio Area: The main tokio crate M-runtime Module: tokio/runtime labels Nov 23, 2022
@carllerche carllerche marked this pull request as ready for review November 24, 2022 00:27
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Ok, this PR should be ready for review. I will fix CI errors as they show up.

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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.

cnt += 1;
}

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.

@carllerche carllerche merged commit 2286273 into master Nov 30, 2022
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@carllerche carllerche deleted the tweak-yield-now branch November 30, 2022 22:21
carllerche added a commit that referenced this pull request 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 added a commit that referenced this pull request 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 added a commit that referenced this pull request 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 added a commit that referenced this pull request 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
crapStone pushed a commit to Calciumdibromid/CaBr2 that referenced this pull request 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 ([#&#8203;5208])
-   io: support vectored writes for `ChildStdin` ([#&#8203;5216])
-   io: fix `async fn ready()` false positive for OS-specific events ([#&#8203;5231])

##### Changed

-   runtime: `yield_now` defers task until after driver poll ([#&#8203;5223])
-   runtime: reduce amount of codegen needed per spawned task ([#&#8203;5213])
-   windows: replace `winapi` dependency with `windows-sys` ([#&#8203;5204])

[#&#8203;5208]: tokio-rs/tokio#5208

[#&#8203;5216]: tokio-rs/tokio#5216

[#&#8203;5213]: tokio-rs/tokio#5213

[#&#8203;5204]: tokio-rs/tokio#5204

[#&#8203;5223]: tokio-rs/tokio#5223

[#&#8203;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>
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