Implementation: `#[feature(sync_nonpoison)]`, `#[feature(nonpoison_mutex)]` #144022

connortsui20 · 2025-07-16T12:43:42Z

Continuation of #134663

Tracking Issue: #134645

This PR implements a new sync/nonpoison module, as well as the nonpoison variant of the Mutex lock.

There are 2 main changes here, the first is the new nonpoison::mutex module, and the second is the mutex integration tests.

For the nonpoison::mutex module, I did my best to align it with the current state of the poison::mutex module. This means that several unstable features (mapped_lock_guards, lock_value_accessors, and mutex_data_ptr) are also in the new nonpoison::mutex module, under their respective feature gates. Everything else in that file is under the correct feature gate (#[unstable(feature = "nonpoison_mutex", issue = "134645")]).

Everything in the nonpoison::mutex file is essentially identical in spirit, as we are simply removing the error case from the original poison::mutex.

The second big change is in the integration tests. I created a macro called that allows us to duplicate tests that are "generic" over the different mutex types, in that the poison mutex is always unwrapped.

I think that there is an argument against doing this, as it can make the tests a bit harder to understand (and language server capabilities are weaker within macros), but I think the benefit of code deduplication here is worth it. Note that it is definitely possible to generalize this (with a few tweaks) to testing the other nonpoison locks when they eventually get implemented, but I'll leave that for a later discussion.

library/std/src/sync/nonpoison/mutex.rs

library/std/tests/sync/mutex.rs

rustbot · 2025-07-18T09:23:59Z

r? @thomcc

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tgross35 · 2025-07-18T16:40:38Z

r? tgross35

tgross35

Looks pretty good to me, most comments here are related to docs. This will need some history cleanup, there isn't any need to preserve the current state of #134663 in history (I assume this was just done for now to show what changed since then)

library/std/src/sync/nonpoison/mod.rs

library/std/src/sync/nonpoison/mutex.rs

library/std/tests/sync/mutex.rs

library/std/tests/sync/lib.rs

EFanZh · 2025-07-23T10:35:15Z

library/std/src/sync/nonpoison/mutex.rs

+        if mem::needs_drop::<T>() {
+            drop(old)
+        }


I think if statement does not do anything. The original implementation uses needs_drop to decide whether to utilize replace, while this implementation will call replace unconditionally, potentially causing some memcpy overhead for trivially drop types.

oh that makes sense, will change!

Could you check if this makes sense?

library/std/src/lib.rs

library/std/tests/sync/lib.rs

library/std/tests/sync/mutex.rs

rustbot · 2025-07-23T20:22:55Z

This PR modifies tests/ui/issues/. If this PR is adding new tests to tests/ui/issues/,
please refrain from doing so, and instead add it to more descriptive subdirectories.

EFanZh · 2025-07-24T08:23:50Z

library/std/src/sync/nonpoison.rs

+
+/// A lock could not be acquired at this time because the operation would otherwise block.
+#[unstable(feature = "sync_nonpoison", issue = "134645")]
+pub struct WouldBlock;


Would it be better if we make the WouldBlock constructor private? So that if we add new fields to it later, it would not cause breaking change.

I would lean on the side of no since TryLockError in the poison module has been around since 1.0 and it has never needed more variants than Poisoned and WouldBlock?

Adds the equivalent `nonpoison` types to the `poison::mutex` module. These types and implementations are gated under the `nonpoison_mutex` feature gate. Co-authored-by: Aandreba <[email protected]>

This commit simply helps discern the actual changes needed to test both poison and nonpoison locks.

Adds tests for the `nonpoison::Mutex` variant by using a macro to duplicate the existing `poison` tests. Note that all of the tests here are adapted from the existing `poison` tests.

bors · 2025-07-26T11:17:52Z

☔ The latest upstream changes (presumably #144488) made this pull request unmergeable. Please resolve the merge conflicts.

Blesses the ui tests that now have a name conflicts (because these types no longer have unique names). The full path distinguishes the different types. Co-authored-by: Trevor Gross <[email protected]>

Also cleans up some other test documentation.

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connortsui20 force-pushed the sync_nonpoison branch 2 times, most recently from e130930 to 804d305 Compare July 18, 2025 08:58

connortsui20 commented Jul 18, 2025

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connortsui20 marked this pull request as ready for review July 18, 2025 09:23

rustbot assigned thomcc Jul 18, 2025

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connortsui20 mentioned this pull request Jul 19, 2025

Tracking Issue for lock_value_accessors #133407

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connortsui20 and others added 5 commits July 26, 2025 13:09

clean up existing poison files

90d299b

add nonpoison::mutex implementation

29658d7

Adds the equivalent `nonpoison` types to the `poison::mutex` module. These types and implementations are gated under the `nonpoison_mutex` feature gate. Co-authored-by: Aandreba <[email protected]>

reorder mutex tests

ff7835f

This commit simply helps discern the actual changes needed to test both poison and nonpoison locks.

add nonpoison and poison mutex tests

2fc79fd

Adds tests for the `nonpoison::Mutex` variant by using a macro to duplicate the existing `poison` tests. Note that all of the tests here are adapted from the existing `poison` tests.

add extra drop and unwind tests

7b0a316

connortsui20 and others added 2 commits July 26, 2025 13:23

Update UI tests

b4efb1c

Blesses the ui tests that now have a name conflicts (because these types no longer have unique names). The full path distinguishes the different types. Co-authored-by: Trevor Gross <[email protected]>

use generic function instead of macro

ac48789

Also cleans up some other test documentation.

connortsui20 force-pushed the sync_nonpoison branch from 19ab767 to ac48789 Compare July 26, 2025 11:23

Implementation: #[feature(sync_nonpoison)], #[feature(nonpoison_mutex)] #144022

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Implementation: #[feature(sync_nonpoison)], #[feature(nonpoison_mutex)] #144022

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Implementation: `#[feature(sync_nonpoison)]`, `#[feature(nonpoison_mutex)]` #144022

Implementation: `#[feature(sync_nonpoison)]`, `#[feature(nonpoison_mutex)]` #144022

connortsui20 commented Jul 16, 2025 •

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