Add fast-path for accessing the current thread id #143069

jsimmons · 2025-06-26T19:51:11Z

Accessing the thread id is often used in profiling and debugging, as well as some approaches for sound single-threaded access to shared data.

Currently the only way to access the thread id is by first obtaining a handle to the current thread. While this is not exactly slow, it does require an atomic inc-ref and dec-ref operation, as well as the injection of Thread's drop code into the caller.

This publicly exposes the existing fast-path for accessing the current thread id.

edit: ACP: rust-lang/libs-team#650

rustbot · 2025-06-26T19:51:16Z

r? @jhpratt

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workingjubilee · 2025-06-26T19:54:24Z

r? libs-api

bors · 2025-08-07T06:27:24Z

☔ The latest upstream changes (presumably #115746) made this pull request unmergeable. Please resolve the merge conflicts.

tgross35 · 2025-09-02T21:05:34Z

Note: I have no idea how these kinds of proposals usually go, but an acp felt overkill for a tiny code change so here we are :)

Could you submit one anyway? It's the easiest way to get something on the radar, and it should be trivial.

tgross35 · 2025-09-05T02:03:55Z

r? tgross35 for after that is done
@rustbot author for the ACP

rustbot · 2025-09-05T02:04:00Z

Reminder, once the PR becomes ready for a review, use @rustbot ready.

joshtriplett · 2025-09-13T08:19:28Z

r=me once the ACP is approved.

joshtriplett · 2025-09-13T08:19:37Z

@bors delegate+

bors · 2025-09-13T08:19:40Z

✌️ @jsimmons, you can now approve this pull request!

If @joshtriplett told you to "r=me" after making some further change, please make that change, then do @bors r=@joshtriplett

jsimmons · 2025-09-30T17:36:30Z

ACP Accepted: rust-lang/libs-team#650

jsimmons · 2025-09-30T17:36:41Z

@bors r=@joshtriplett

bors · 2025-09-30T17:36:44Z

📌 Commit 82eb244 has been approved by joshtriplett

It is now in the queue for this repository.

joboet · 2025-09-30T18:11:25Z

@bors r-
The tracking issue number is missing from the #[unstable] attributes.

jfrimmel · 2025-09-30T18:23:46Z

library/std/src/thread/current.rs

+/// });
+///
+/// let other_thread_id = other_thread.join().unwrap();
+/// assert!(thread::current_id() != other_thread_id);


Suggested change

/// assert!(thread::current_id() != other_thread_id);

/// assert_ne!(thread::current_id(), other_thread_id);

rustbot · 2025-09-30T18:40:44Z

This PR was rebased onto a different master commit. Here's a range-diff highlighting what actually changed.

Rebasing is a normal part of keeping PRs up to date, so no action is needed—this note is just to help reviewers.

Accessing the thread id is often used in profiling and debugging, as well as some approaches for sound single-threaded access to data. Currently the only way to access the thread id is by first obtaining a handle to the current thread. While this is not exactly slow, it does require an atomic inc-ref and dec-ref operation, as well as the injection of `Thread`'s drop code into the caller. This publicly exposes the existing fast-path for accessing the current thread id.

tgross35 · 2025-09-30T19:15:28Z

@bors r=joshtriplett,tgross35

bors · 2025-09-30T19:15:31Z

📌 Commit cbaec31 has been approved by joshtriplett,tgross35

It is now in the queue for this repository.

Rollup of 6 pull requests Successful merges: - #143069 (Add fast-path for accessing the current thread id) - #146518 (Improve the documentation around `ZERO_AR_DATE`) - #146596 (Add a dummy codegen backend) - #146617 (Don’t suggest foreign `doc(hidden)` types in "the following other types implement trait" diagnostics) - #146635 (cg_llvm: Stop using `as_c_char_ptr` for coverage-related bindings) - #147184 (Fix the bevy implied bounds hack for the next solver) r? `@ghost` `@rustbot` modify labels: rollup

Rollup merge of #143069 - jsimmons:current-thread-id-accessor, r=joshtriplett,tgross35 Add fast-path for accessing the current thread id Accessing the thread id is often used in profiling and debugging, as well as some approaches for sound single-threaded access to shared data. Currently the only way to access the thread id is by first obtaining a handle to the current thread. While this is not exactly slow, it does require an atomic inc-ref and dec-ref operation, as well as the injection of `Thread`'s drop code into the caller. This publicly exposes the existing fast-path for accessing the current thread id. edit: ACP: rust-lang/libs-team#650

rustbot assigned jhpratt Jun 26, 2025

rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. T-libs Relevant to the library team, which will review and decide on the PR/issue. labels Jun 26, 2025

rustbot added the T-libs-api Relevant to the library API team, which will review and decide on the PR/issue. label Jun 26, 2025

rustbot assigned m-ou-se and unassigned jhpratt Jun 26, 2025

rustbot assigned tgross35 and unassigned m-ou-se Sep 5, 2025

rustbot added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Sep 5, 2025

tgross35 added the S-waiting-on-ACP Status: PR has an ACP and is waiting for the ACP to complete. label Sep 5, 2025

jsimmons mentioned this pull request Sep 7, 2025

Add direct access to the thread id rust-lang/libs-team#650

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jsimmons force-pushed the current-thread-id-accessor branch from 175584f to 82eb244 Compare September 7, 2025 19:47

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jsimmons mentioned this pull request Sep 30, 2025

Tracking Issue for current_thread_id #147194

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bors added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. and removed S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. labels Sep 30, 2025

jsimmons force-pushed the current-thread-id-accessor branch from 82eb244 to 5400f9e Compare September 30, 2025 18:19

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jfrimmel reviewed Sep 30, 2025

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tgross35 removed the S-waiting-on-ACP Status: PR has an ACP and is waiting for the ACP to complete. label Sep 30, 2025

jsimmons force-pushed the current-thread-id-accessor branch from 5400f9e to c081c87 Compare September 30, 2025 18:40

jsimmons force-pushed the current-thread-id-accessor branch from c081c87 to cbaec31 Compare September 30, 2025 18:51

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matthiaskrgr mentioned this pull request Sep 30, 2025

Rollup of 6 pull requests #147198

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bors merged commit 3e621b3 into rust-lang:master Oct 1, 2025
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rustbot added this to the 1.92.0 milestone Oct 1, 2025

	/// assert!(thread::current_id() != other_thread_id);
	/// assert_ne!(thread::current_id(), other_thread_id);

Add fast-path for accessing the current thread id #143069

Add fast-path for accessing the current thread id #143069

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jsimmons commented Jun 26, 2025 •

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