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Solve deadlock in Semaphore #5475

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merged 3 commits into from
Feb 19, 2023
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amab8901
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@amab8901 amab8901 commented Feb 18, 2023

Motivation

#5429

solving the semaphore deadlock

Solution

create a test to check for deadlock. Then save old value of waker when updating the waker value. Then drop the waiters before dropping the old waker inside the waiter (this is how I understood it).
PS: I'm kinda new to this so may be good for a pro to double check if I used the right approach

@github-actions github-actions bot added the R-loom Run loom tests on this PR label Feb 18, 2023
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Please modify the PR description to refer to the issue this is related to using the keyword feature.

@Darksonn Darksonn added A-tokio Area: The main tokio crate M-sync Module: tokio/sync labels Feb 18, 2023
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There's a rustfmt failure. Please see this page for instructions on running rustfmt in Tokio's repository.

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Thanks.

@Darksonn Darksonn merged commit 901f6d2 into tokio-rs:master Feb 19, 2023
amab8901 added a commit to amab8901/tokio that referenced this pull request Feb 27, 2023
Noah-Kennedy added a commit that referenced this pull request Mar 1, 2023
# 1.26.0 (March 1st, 2023)

### Fixed

- sync: don't leak tracing spans in mutex guards ([#5469])
- sync: drop wakers after unlocking the mutex in Notify ([#5471])
- sync: drop wakers outside lock in semaphore ([#5475])
- macros: fix empty `join!` and `try_join!` ([#5504])

### Added

- fs: add `fs::try_exists` ([#4299])
- net: add types for named unix pipes ([#5351])
- sync: add `MappedOwnedMutexGuard` ([#5474])

### Documented

- task: clarify what happens to spawned work during runtime shutdown ([#5394])
- task: clarify `process::Command` docs (#5406) ([#5413])
- sync: add doc aliases for `blocking_*` methods ([#5448])
- task: fix wording with 'unsend' ([#5452])
- signal: updated Documentation for Signals ([#5459])
- sync: fix docs for Send/Sync bounds in broadcast ([#5480])
- io: improve AsyncFd example ([#5481])
- tokio: document supported platforms ([#5483])
- runtime: document the nature of the main future ([#5494])
- sync: document drop behavior for channels ([#5497])
- time: document immediate completion guarantee for timeouts ([#5509])
- runtime: remove extra period in docs ([#5511])

### Changed

- net: use Message Read Mode for named pipes ([#5350])
- chore: update windows-sys to 0.45 ([#5386])
- sync: mark lock guards with `#[clippy::has_significant_drop]` ([#5422])
- sync: reduce contention in watch channel ([#5464])
- time: remove cache padding in timer entries ([#5468])
- time: Improve `Instant::now()` perf with test-util ([#5513])

### Internal Changes
- tests: port proptest fuzz harnesses to use cargo-fuzz ([#5392])
- time: don't store deadline twice in sleep entries ([#5410])
- rt: remove Arc from Clock ([#5434])
- sync: make `notify_waiters` calls atomic ([#5458])
- net: refactor named pipe builders to not use bitfields ([#5477])
- io: use `poll_fn` in `copy_bidirectional` ([#5486])
- fs: add more tests for filesystem functionality ([#5493])
- net: fix test compilation failure ([#5506])
- io: ignore SplitByUtf8BoundaryIfWindows test on miri ([#5507])

### Unstable

- metrics: add a new metric for budget exhaustion yields ([#5517])

[#4299]: #4299
[#5350]: #5350
[#5351]: #5351
[#5386]: #5386
[#5392]: #5392
[#5394]: #5394
[#5410]: #5410
[#5413]: #5413
[#5422]: #5422
[#5434]: #5434
[#5448]: #5448
[#5452]: #5452
[#5458]: #5458
[#5459]: #5459
[#5464]: #5464
[#5468]: #5468
[#5469]: #5469
[#5471]: #5471
[#5474]: #5474
[#5475]: #5475
[#5477]: #5477
[#5480]: #5480
[#5481]: #5481
[#5483]: #5483
[#5486]: #5486
[#5493]: #5493
[#5494]: #5494
[#5497]: #5497
[#5504]: #5504
[#5506]: #5506
[#5507]: #5507
[#5509]: #5509
[#5511]: #5511
[#5513]: #5513
[#5517]: #5517
Noah-Kennedy added a commit that referenced this pull request Mar 1, 2023
# 1.26.0 (March 1st, 2023)

### Fixed

- macros: fix empty `join!` and `try_join!` ([#5504])
- sync: don't leak tracing spans in mutex guards ([#5469])
- sync: drop wakers after unlocking the mutex in Notify ([#5471])
- sync: drop wakers outside lock in semaphore ([#5475])

### Added

- fs: add `fs::try_exists` ([#4299])
- net: add types for named unix pipes ([#5351])
- sync: add `MappedOwnedMutexGuard` ([#5474])

### Changed

- chore: update windows-sys to 0.45 ([#5386])
- net: use Message Read Mode for named pipes ([#5350])
- sync: mark lock guards with `#[clippy::has_significant_drop]` ([#5422])
- sync: reduce contention in watch channel ([#5464])
- time: remove cache padding in timer entries ([#5468])
- time: Improve `Instant::now()` perf with test-util ([#5513])

### Internal Changes

- io: use `poll_fn` in `copy_bidirectional` ([#5486])
- net: refactor named pipe builders to not use bitfields ([#5477])
- rt: remove Arc from Clock ([#5434])
- sync: make `notify_waiters` calls atomic ([#5458])
- time: don't store deadline twice in sleep entries ([#5410])

### Unstable

- metrics: add a new metric for budget exhaustion yields ([#5517])

### Documented

- io: improve AsyncFd example ([#5481])
- runtime: document the nature of the main future ([#5494])
- runtime: remove extra period in docs ([#5511])
- signal: updated Documentation for Signals ([#5459])
- sync: add doc aliases for `blocking_*` methods ([#5448])
- sync: fix docs for Send/Sync bounds in broadcast ([#5480])
- sync: document drop behavior for channels ([#5497])
- task: clarify what happens to spawned work during runtime shutdown ([#5394])
- task: clarify `process::Command` docs ([#5413])
- task: fix wording with 'unsend' ([#5452])
- time: document immediate completion guarantee for timeouts ([#5509])
- tokio: document supported platforms ([#5483])

[#4299]: #4299
[#5350]: #5350
[#5351]: #5351
[#5386]: #5386
[#5394]: #5394
[#5410]: #5410
[#5413]: #5413
[#5422]: #5422
[#5434]: #5434
[#5448]: #5448
[#5452]: #5452
[#5458]: #5458
[#5459]: #5459
[#5464]: #5464
[#5468]: #5468
[#5469]: #5469
[#5471]: #5471
[#5474]: #5474
[#5475]: #5475
[#5477]: #5477
[#5480]: #5480
[#5481]: #5481
[#5483]: #5483
[#5486]: #5486
[#5494]: #5494
[#5497]: #5497
[#5504]: #5504
[#5509]: #5509
[#5511]: #5511
[#5513]: #5513
[#5517]: #5517
Noah-Kennedy added a commit that referenced this pull request Mar 1, 2023
# 1.26.0 (March 1st, 2023)

### Fixed

- macros: fix empty `join!` and `try_join!` ([#5504])
- sync: don't leak tracing spans in mutex guards ([#5469])
- sync: drop wakers after unlocking the mutex in Notify ([#5471])
- sync: drop wakers outside lock in semaphore ([#5475])

### Added

- fs: add `fs::try_exists` ([#4299])
- net: add types for named unix pipes ([#5351])
- sync: add `MappedOwnedMutexGuard` ([#5474])

### Changed

- chore: update windows-sys to 0.45 ([#5386])
- net: use Message Read Mode for named pipes ([#5350])
- sync: mark lock guards with `#[clippy::has_significant_drop]` ([#5422])
- sync: reduce contention in watch channel ([#5464])
- time: remove cache padding in timer entries ([#5468])
- time: Improve `Instant::now()` perf with test-util ([#5513])

### Internal Changes

- io: use `poll_fn` in `copy_bidirectional` ([#5486])
- net: refactor named pipe builders to not use bitfields ([#5477])
- rt: remove Arc from Clock ([#5434])
- sync: make `notify_waiters` calls atomic ([#5458])
- time: don't store deadline twice in sleep entries ([#5410])

### Unstable

- metrics: add a new metric for budget exhaustion yields ([#5517])

### Documented

- io: improve AsyncFd example ([#5481])
- runtime: document the nature of the main future ([#5494])
- runtime: remove extra period in docs ([#5511])
- signal: updated Documentation for Signals ([#5459])
- sync: add doc aliases for `blocking_*` methods ([#5448])
- sync: fix docs for Send/Sync bounds in broadcast ([#5480])
- sync: document drop behavior for channels ([#5497])
- task: clarify what happens to spawned work during runtime shutdown ([#5394])
- task: clarify `process::Command` docs ([#5413])
- task: fix wording with 'unsend' ([#5452])
- time: document immediate completion guarantee for timeouts ([#5509])
- tokio: document supported platforms ([#5483])

[#4299]: #4299
[#5350]: #5350
[#5351]: #5351
[#5386]: #5386
[#5394]: #5394
[#5410]: #5410
[#5413]: #5413
[#5422]: #5422
[#5434]: #5434
[#5448]: #5448
[#5452]: #5452
[#5458]: #5458
[#5459]: #5459
[#5464]: #5464
[#5468]: #5468
[#5469]: #5469
[#5471]: #5471
[#5474]: #5474
[#5475]: #5475
[#5477]: #5477
[#5480]: #5480
[#5481]: #5481
[#5483]: #5483
[#5486]: #5486
[#5494]: #5494
[#5497]: #5497
[#5504]: #5504
[#5509]: #5509
[#5511]: #5511
[#5513]: #5513
[#5517]: #5517
This was referenced Apr 8, 2025
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