Use 64-bit futex syscalls on RV32 Linux by TechnoPorg · Pull Request #164748 · rust-lang/rust

TechnoPorg · 2026-10-22T14:18:15Z

This changes riscv32 Linux targets to use the SYS_futex_time64 syscall instead of SYS_futex in the standard library to fix compilation after rust-lang/libc#5455.

libc::timespec has a c_long for nanoseconds on 32-bit targets right now, whereas the kernel uses long long. I'm not sure whether this is a problem or not?

I'm also curious whether using the time64 syscall on all 32-bit targets is a desired change.

r? tgross35

rustbot · 2026-10-22T14:18:19Z

miri is developed in its own repository. If the Miri part of this change can be broken out, consider making this change to rust-lang/miri instead. However, if Miri needs adjusting for rustc changes, just ignore this message.

cc @rust-lang/miri

These commits modify the Cargo.lock file. Unintentional changes to Cargo.lock can be introduced when switching branches and rebasing PRs.

If this was unintentional then you should revert the changes before this PR is merged.
Otherwise, you can ignore this comment.

rustbot · 2026-10-22T14:18:23Z

tgross35 is currently at their maximum review capacity.
They may take a while to respond.

tgross35

The libs portion looks fine to me, but this is mostly a Miri PR. I think you should probably file it at the Miri repo since I believe more arches are tested there.

r? miri

View changes since this review

tgross35 · 2026-10-22T15:32:15Z

+    // riscv32 uses a 64-bit `libc::timespec`, and only exposes the `SYS_futex_time64` syscall,
+    // whereas other 32-bit targets use their 32-bit `libc::timespec` with `SYS_futex`, and require
+    // opting into a 64-bit `timespec` with the `SYS_futex_time64` syscall.
+    target_arch = "riscv32" => {
+        use libc::SYS_futex_time64 as SYS_futex;
+    }
+    _ => {
+        use libc::SYS_futex;
+    }


This is a rather confusing comment, can it be simplified?

I wanted to clarify that the libc::timespec struct is ABI-compatible with the syscall that gets selected by this cfg_select!, since that tripped me up. I removed the timespec parts but if you have better wording suggestions I'm happy to implement them.

rustbot · 2026-10-22T15:50:05Z

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

tgross35 · 2026-10-22T15:52:26Z

Actually, why are Miri changes needed at all for the std fix? We aren't running tests against rv32 in this repo as far as I'm aware

TechnoPorg · 2026-10-22T16:11:22Z

Actually, why are Miri changes needed at all for the std fix? We aren't running tests against rv32 in this repo as far as I'm aware

I just grepped for SYS_futex with the intent of fixing everywhere it was used. But it seems the Miri changes would be more involved than I thought, so maybe instead I'll just file the lack of SYS_futex_time64 support as a Miri issue for now.

RalfJung · 2026-10-22T17:07:04Z

rv32 is not a supported Miri target currently. I am not even sure if we test 64bit riscv....

TechnoPorg · 2026-10-22T17:36:52Z

I've gotten rid of my ill-fated Miri changes and if they happen at all, they can happen in a separate PR to the miri repository.

rv32 is not a supported Miri target currently. I am not even sure if we test 64bit riscv....

Does Miri support any 32-bit Linux targets? If not the SYS_futex_time64 syscall handling wouldn't even be necessary.

tgross35

Thanks!
@bors r+

View changes since this review

rust-bors · 2026-10-22T17:40:57Z

📌 Commit c860e0d has been tentatively approved by tgross35

It will be put into the queue for this repository once PR CI succeeds.

tgross35 · 2026-10-22T17:43:37Z

Does Miri support any 32-bit Linux targets? If not the SYS_futex_time64 syscall handling wouldn't even be necessary.

Atleast i686 and arm32 are https://github.com/rust-lang/miri/blob/eaacf5fb522e50f25aa0b12db34bc99c0bd38068/ci/ci.sh#L159-L191

RalfJung · 2026-10-22T19:55:53Z

Turns out we do check riscv64a23-unknown-linux-gnu in CI.

But officially we only support tier 1 targets, and then we check some tier 2 targets but that's best-effort and will be disabled if a fix would be too much work and block other work. So yes we do support i686-linux.

Use 64-bit futex syscalls on RV32 Linux Closes rust-lang#164694 This changes riscv32 Linux targets to use the `SYS_futex_time64` syscall instead of `SYS_futex` in the standard library to fix compilation after rust-lang/libc#5455. `libc::timespec` has a `c_long` for nanoseconds on 32-bit targets right now, whereas the kernel uses `long long`. I'm not sure whether this is a problem or not? I'm also curious whether using the time64 syscall on _all_ 32-bit targets is a desired change. r? tgross35

…uwer Rollup of 5 pull requests Successful merges: - #164748 (Use 64-bit futex syscalls on RV32 Linux) - #159689 (Account for missing turbofish in resolve errors) - #164733 (Include `deprecated` attributes in `rustc_resolve` intra-doc link resolution) - #164754 (Update outdated/incorrect unstable tracking issue links) - #164761 ([tiny] Properly format return type in lifetime error with backticks)

Use 64-bit futex syscalls on RV32 Linux Closes #164694 This changes riscv32 Linux targets to use the `SYS_futex_time64` syscall instead of `SYS_futex` in the standard library to fix compilation after rust-lang/libc#5455. `libc::timespec` has a `c_long` for nanoseconds on 32-bit targets right now, whereas the kernel uses `long long`. I'm not sure whether this is a problem or not? I'm also curious whether using the time64 syscall on _all_ 32-bit targets is a desired change. r? tgross35

rust-bors · 2026-10-23T08:35:48Z

💔 Test for 0ad4612 failed: CI. Failed job:

auto - dist-powerpc64-linux-musl (web logs, enhanced plaintext logs)

JonathanBrouwer · 2026-10-23T08:38:33Z

💔 I suspect this PR failed tests as part of a rollup
@bors r-

After fixing the problem, consider running a try job for the failed job before re-approving.

Link to failure: #164780 (comment)

rust-bors · 2026-10-23T08:38:42Z

This PR was contained in a rollup (#164780), which was unapproved.

View changes since this unapproval

TechnoPorg · 2026-10-23T13:26:46Z

rustix <1.1.5 is incompatible with libc >=0.2.190 (bytecodealliance/rustix#1676), so I've bumped it in the lockfile as well.

If someone with try build permissions could run the failed job again to see if this fixes it, that would be appreciated.

JonathanBrouwer · 2026-10-23T13:33:19Z

@bors try jobs=dist-powerpc64-linux-musl

Use 64-bit futex syscalls on RV32 Linux try-job: dist-powerpc64-linux-musl

rust-bors · 2026-10-23T15:20:26Z

☀️ Try build successful (CI)
Build commit: 240af90 (240af9030f4cf2e710f13aab9d136dc893dc05e7)
Base parent: a0326ca (a0326caa8961d2900534b29e10a57afcdcf65135)

TechnoPorg · 2026-10-23T15:49:27Z

@rustbot ready

tgross35 · 2026-10-23T21:00:46Z

@bors r+

rust-bors · 2026-10-23T21:00:49Z

📌 Commit 093a6f1 has been approved by tgross35

It is now in the queue for this repository.

…uwer Rollup of 5 pull requests Successful merges: - #163766 (Outline constant messages from panicking macros) - #147368 (Add extra `unchecked_disjoint_bitor` implementations.) - #164748 (Use 64-bit futex syscalls on RV32 Linux) - #164520 (powerpc: implement c-variadic correctly for softfloat targets) - #164671 (add maintainers for tier 2 riscv64 targets (baremetal only))

Rollup merge of #164748 - TechnoPorg:64-bit-futex, r=tgross35 Use 64-bit futex syscalls on RV32 Linux Closes #164694 This changes riscv32 Linux targets to use the `SYS_futex_time64` syscall instead of `SYS_futex` in the standard library to fix compilation after rust-lang/libc#5455. `libc::timespec` has a `c_long` for nanoseconds on 32-bit targets right now, whereas the kernel uses `long long`. I'm not sure whether this is a problem or not? I'm also curious whether using the time64 syscall on _all_ 32-bit targets is a desired change. r? tgross35

…uwer Rollup of 5 pull requests Successful merges: - rust-lang/rust#163766 (Outline constant messages from panicking macros) - rust-lang/rust#147368 (Add extra `unchecked_disjoint_bitor` implementations.) - rust-lang/rust#164748 (Use 64-bit futex syscalls on RV32 Linux) - rust-lang/rust#164520 (powerpc: implement c-variadic correctly for softfloat targets) - rust-lang/rust#164671 (add maintainers for tier 2 riscv64 targets (baremetal only))

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 Oct 22, 2026

rustbot assigned tgross35 Oct 22, 2026

This comment has been minimized.

Sign in to view

tgross35 requested changes Oct 22, 2026

View reviewed changes

rustbot assigned saethlin and unassigned tgross35 Oct 22, 2026

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 Oct 22, 2026

TechnoPorg changed the title ~~Use 64-bit futex syscalls on 32-bit Linux targets~~ Use 64-bit futex syscalls on RV32 Linux Oct 22, 2026

This comment has been minimized.

Sign in to view

Use 64-bit time for futex syscalls on RV32

c860e0d

TechnoPorg force-pushed the 64-bit-futex branch from 13eac20 to c860e0d Compare October 22, 2026 17:32

tgross35 approved these changes Oct 22, 2026

View reviewed changes

rust-bors Bot added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Oct 22, 2026

TechnoPorg mentioned this pull request Oct 22, 2026

32-bit Linux (glibc): setting file times past 2038 fails because the __futimens64 shim is missing rust-lang/miri#5385

Open

jhpratt mentioned this pull request Oct 22, 2026

Rollup of 5 pull requests #164773

Closed

This comment has been minimized.

Sign in to view

rust-bors Bot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. and removed S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. labels Oct 23, 2026

rust-bors Bot 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 Oct 23, 2026

fix: update rustix to version compatible with latest libc

093a6f1

rust-bors Bot pushed a commit that referenced this pull request Oct 23, 2026

Auto merge of #164748 - TechnoPorg:64-bit-futex, r=<try>

240af90

Use 64-bit futex syscalls on RV32 Linux try-job: dist-powerpc64-linux-musl

This comment has been minimized.

Sign in to view

rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. and removed S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Oct 23, 2026

rust-bors Bot added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Oct 23, 2026

JonathanBrouwer mentioned this pull request Oct 23, 2026

Rollup of 5 pull requests #164826

Merged

rust-bors Bot merged commit 23586b2 into rust-lang:main Oct 24, 2026
15 checks passed

rustbot added this to the 1.101.0 milestone Oct 24, 2026

Conversation

TechnoPorg commented Oct 22, 2026 • edited by rustbot Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Uh oh!

rustbot commented Oct 22, 2026

Uh oh!

rustbot commented Oct 22, 2026

Uh oh!

This comment has been minimized.

tgross35 left a comment • edited by rustbot Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Uh oh!

tgross35 Oct 22, 2026

Choose a reason for hiding this comment

Uh oh!

TechnoPorg Oct 22, 2026

Choose a reason for hiding this comment

Uh oh!

Uh oh!

Uh oh!

Uh oh!

rustbot commented Oct 22, 2026

Uh oh!

tgross35 commented Oct 22, 2026

Uh oh!

TechnoPorg commented Oct 22, 2026

Uh oh!

This comment has been minimized.

RalfJung commented Oct 22, 2026 via email

Uh oh!

TechnoPorg commented Oct 22, 2026

Uh oh!

tgross35 left a comment • edited by rustbot Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Choose a reason for hiding this comment

Uh oh!

rust-bors Bot commented Oct 22, 2026

Uh oh!

tgross35 commented Oct 22, 2026

Uh oh!

RalfJung commented Oct 22, 2026

Uh oh!

This comment has been minimized.

This comment has been minimized.

rust-bors Bot commented Oct 23, 2026

Uh oh!

JonathanBrouwer commented Oct 23, 2026

Uh oh!

rust-bors Bot commented Oct 23, 2026

Uh oh!

TechnoPorg commented Oct 23, 2026

Uh oh!

JonathanBrouwer commented Oct 23, 2026

Uh oh!

This comment has been minimized.

rust-bors Bot commented Oct 23, 2026

Uh oh!

TechnoPorg commented Oct 23, 2026

Uh oh!

tgross35 commented Oct 23, 2026

Uh oh!

rust-bors Bot commented Oct 23, 2026

Uh oh!

Uh oh!

Reviewers

Uh oh!

Assignees

Labels

Projects

Milestone

Development

Uh oh!

7 participants

TechnoPorg commented Oct 22, 2026 •

edited by rustbot

Loading

tgross35 left a comment •

edited by rustbot

Loading

tgross35 left a comment •

edited by rustbot

Loading