Make {Mutex, Condvar, RwLock}::new() const. #97791

m-ou-se · 2022-06-06T12:02:26Z

This makes it possible to have static M: Mutex<_> = Mutex::new(..); 🎉

Our implementations on Linux, on Windows, and various BSDs and some tier 3 platforms have already been using a non-allocating const-constructible implementation. As of #97647, the remaining platforms (most notably macOS) now have a const-constructible implementation as well. This means we can finally make these functions publicly const.

Tracking issue: #93740

m-ou-se · 2022-06-06T12:02:39Z

@rfcbot merge

rfcbot · 2022-06-06T12:02:41Z

Team member @m-ou-se has proposed to merge this. The next step is review by the rest of the tagged team members:

No concerns currently listed.

Once a majority of reviewers approve (and at most 2 approvals are outstanding), this will enter its final comment period. If you spot a major issue that hasn't been raised at any point in this process, please speak up!

See this document for info about what commands tagged team members can give me.

rfcbot · 2022-06-07T15:26:39Z

🔔 This is now entering its final comment period, as per the review above. 🔔

rfcbot · 2022-06-17T15:29:36Z

The final comment period, with a disposition to merge, as per the review above, is now complete.

As the automated representative of the governance process, I would like to thank the author for their work and everyone else who contributed.

This will be merged soon.

m-ou-se · 2022-06-18T16:29:01Z

@bors r+

bors · 2022-06-18T16:29:03Z

📌 Commit edae495 has been approved by m-ou-se

bors · 2022-06-19T08:20:38Z

⌛ Testing commit edae495 with merge 15fc228...

bors · 2022-06-19T12:28:53Z

☀️ Test successful - checks-actions
Approved by: m-ou-se
Pushing 15fc228 to master...

rust-timer · 2022-06-19T13:47:08Z

Finished benchmarking commit (15fc228): comparison url.

Instruction count

Primary benchmarks: no relevant changes found
Secondary benchmarks: 🎉 relevant improvement found

	mean¹	max	count²
Regressions 😿 (primary)	N/A	N/A	0
Regressions 😿 (secondary)	N/A	N/A	0
Improvements 🎉 (primary)	N/A	N/A	0
Improvements 🎉 (secondary)	-1.7%	-1.7%	1
All 😿🎉 (primary)	N/A	N/A	0

Max RSS (memory usage)

Results

Primary benchmarks: 😿 relevant regression found
Secondary benchmarks: no relevant changes found

	mean¹	max	count²
Regressions 😿 (primary)	0.0%	0.0%	1
Regressions 😿 (secondary)	N/A	N/A	0
Improvements 🎉 (primary)	N/A	N/A	0
Improvements 🎉 (secondary)	N/A	N/A	0
All 😿🎉 (primary)	0.0%	0.0%	1

Cycles

Results

Primary benchmarks: 🎉 relevant improvement found
Secondary benchmarks: 🎉 relevant improvement found

	mean¹	max	count²
Regressions 😿 (primary)	N/A	N/A	0
Regressions 😿 (secondary)	N/A	N/A	0
Improvements 🎉 (primary)	-3.3%	-3.3%	1
Improvements 🎉 (secondary)	-2.3%	-2.3%	1
All 😿🎉 (primary)	-3.3%	-3.3%	1

If you disagree with this performance assessment, please file an issue in rust-lang/rustc-perf.

@rustbot label: -perf-regression

the arithmetic mean of the percent change ↩ ↩² ↩³
number of relevant changes ↩ ↩² ↩³

rust-lang/rust#97791 appears to have broken -Z build-std (?)

make Condvar, Mutex, RwLock const constructors work with the `unsupported` impl applying this patch locally to the `rust-src` component fixes rust-lang#98378 however, the solution seems wrong to me because PR rust-lang#97791 didn't add any `rustc_const_stable` attribute to underlying implementations like `std::sys::unix::futex`, so I must be missing something about how const-stability is checked ... maybe the `restricted_std` feature (gate?) has an effect? fixes rust-lang#98378 fixes rust-lang#98293 (probably)

pronebird · 2024-02-10T14:21:50Z

It raised my eyebrows when static mutex just worked, that's how I found this page! Holy shit, great work! 💪

…lnay Make `Barrier::new()` const I guess this was just missed in rust-lang#97791? `@rustbot` label T-libs-api -T-libs

m-ou-se added 2 commits June 6, 2022 13:49

Make all {Mutex, Condvar, RwLock}::new #[inline].

acc3ab4

Make {Mutex, Condvar, RwLock}::new() const.

edae495

m-ou-se added T-libs-api Relevant to the library API team, which will review and decide on the PR/issue. needs-fcp This change is insta-stable, or significant enough to need a team FCP to proceed. labels Jun 6, 2022

m-ou-se self-assigned this Jun 6, 2022

rust-highfive added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Jun 6, 2022

rfcbot added proposed-final-comment-period Proposed to merge/close by relevant subteam, see T-<team> label. Will enter FCP once signed off. disposition-merge This issue / PR is in PFCP or FCP with a disposition to merge it. labels Jun 6, 2022

m-ou-se mentioned this pull request Jun 6, 2022

Tracking issue for improving std::sync::{Mutex, RwLock, Condvar} #93740

Closed

63 tasks

m-ou-se added S-waiting-on-fcp Status: PR is in FCP and is awaiting for FCP to complete. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Jun 7, 2022

rfcbot added the final-comment-period In the final comment period and will be merged soon unless new substantive objections are raised. label Jun 7, 2022

rfcbot removed the proposed-final-comment-period Proposed to merge/close by relevant subteam, see T-<team> label. Will enter FCP once signed off. label Jun 7, 2022

memoryruins mentioned this pull request Jun 18, 2022

Switch back to std::sync::Mutex? tokio-rs/tokio#4623

Closed

bors added the S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. label Jun 18, 2022

bors added the merged-by-bors This PR was explicitly merged by bors. label Jun 19, 2022

bors merged commit 15fc228 into rust-lang:master Jun 19, 2022

rustbot added this to the 1.63.0 milestone Jun 19, 2022

mejrs mentioned this pull request Jun 19, 2022

Upstream issues for wasm32-emscripten support: instant library and emscripten_get_now PyO3/pyo3#2417

Closed

m-ou-se deleted the const-locks branch June 19, 2022 20:52

tmandry mentioned this pull request Jun 20, 2022

Use futex based thread parker on Fuchsia. #96768

Merged

japaric added a commit to japaric/cargo-call-stack that referenced this pull request Jun 22, 2022

pin nightly version in CI

8c6d14a

rust-lang/rust#97791 appears to have broken -Z build-std (?)

This was referenced Jun 22, 2022

libstd: -Z build-std is now broken for Cortex-M targets #98378

Closed

make Condvar, Mutex, RwLock const constructors work with the unsupported impl #98457

Merged

dtolnay mentioned this pull request Jul 4, 2022

Feature request: Make Mutex::new/RwLock::new const. #73714

Closed

wyatt-herkamp mentioned this pull request Jul 31, 2022

winit 0.27 Update and raw-window-handle 0.5 gfx-rs/wgpu#2918

Merged

3 tasks

apiraino removed the to-announce Announce this issue on triage meeting label Sep 8, 2022

Darksonn mentioned this pull request Sep 24, 2022

Tracking Issue for Mutex::new() as const fn #66806

Closed

Jules-Bertholet mentioned this pull request Jan 3, 2024

Make Barrier::new() const #119536

Merged

pronebird mentioned this pull request Feb 10, 2024

Introduce cancellation token and reduce amount of code tun2proxy/tun2proxy#88

Merged

bors added a commit to rust-lang-ci/rust that referenced this pull request Feb 23, 2024

Auto merge of rust-lang#119536 - Jules-Bertholet:const-barrier, r=dto…

8f359be

…lnay Make `Barrier::new()` const I guess this was just missed in rust-lang#97791? `@rustbot` label T-libs-api -T-libs

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Make {Mutex, Condvar, RwLock}::new() const. #97791

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Make {Mutex, Condvar, RwLock}::new() const. #97791

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