Specialize sleep_until implementation for unix (except mac) #141829

dvdsk · 2025-05-31T19:38:39Z

related tracking issue: #113752
Supersedes #118480 for the reasons see: #113752 (comment)

Replaces the generic catch all implementation with target_os specific ones for: linux/netbsd/freebsd/android/solaris/illumos etc. Other platforms like wasi, macos/ios/tvos/watchos and windows will follow in later separate PR's (once this is merged).

rustbot · 2025-05-31T19:38:43Z

r? @tgross35

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dvdsk · 2025-05-31T19:39:32Z

r? @cuviper

dvdsk · 2025-05-31T22:38:40Z

This can be done without touching all pal's, ill be doing that tomorrow, now its bed time 😴

edit: I was mistaken, tidy does not allow #[cfg(...)] in strc/thread/mod.rs probably for a good reason. Therefore we need a trivial not platform specific sleep_until in every pal that does not have a specialized one.

library/std/src/time.rs

library/std/src/sys/pal/unix/time.rs

library/std/src/sys/pal/unix/thread.rs

Except for unix they are all copies of the existing non platform specific implementation. This is the only way since tidy does not allow `#[cfg(target_os = ` in src/thread/mod.rs. Once this is merged more specializations will follow.

Co-authored-by: Josh Stone <cuviper@gmail.com>

library/std/src/sys/pal/unix/thread.rs

library/std/src/thread/mod.rs

library/std/src/time.rs

Co-authored-by: Jonas Böttiger <jonasboettiger@icloud.com> - use the internal platform specific Instant::CLOCK_ID - skip allow(unused) on on platform that uses it such that it can not become dead code - sleep_until: remove leftover links

library/std/src/sys/pal/unix/thread.rs

library/std/src/sys/pal/unix/time.rs

- In contradiction to nanosleep clock_nanosleep returns the error directly and does not require a call to `os::errno()`. - The last argument to clock_nanosleep can be NULL removing the need for mutating the timespec. - Missed an `allow(unused)` that could be made conditional.

dvdsk · 2025-06-11T23:17:44Z

library/std/src/sys/pal/unix/thread.rs

+                if res == 0 {
+                    break;
+                } else {
+                    assert_eq!(res, libc::EINTR);


Would it make sense to add a comment or message to the assert explaining why we should only get res == 0 or res == EINTR? I thought about adding one however sleep does not do so, would it be to verbose?

Sure, a succinct comment would be good.

cuviper · 2025-06-12T21:19:20Z

library/std/src/sys/pal/unix/thread.rs

+        let Some(ts) = deadline.into_inner().into_timespec().to_timespec() else {
+            // The deadline is further in the future then can be passed to
+            // clock_nanosleep. We have to use Self::sleep intead. This might
+            // happen on 32 bit platforms, especially closer to 2038.


We don't necessarily need to deal with this now, but 32-bit glibc also has __clock_nanosleep_time64 for future-proofing, which could use like this __clock_gettime64 code:

rust/library/std/src/sys/pal/unix/time.rs

Lines 103 to 128 in 6c8138d

// Try to use 64-bit time in preparation for Y2038.

#[cfg(all(

target_os = "linux",

target_env = "gnu",

target_pointer_width = "32",

not(target_arch = "riscv32")

))]

{

use crate::sys::weak::weak;

// __clock_gettime64 was added to 32-bit arches in glibc 2.34,

// and it handles both vDSO calls and ENOSYS fallbacks itself.

weak!(

fn __clock_gettime64(

clockid: libc::clockid_t,

tp: *mut __timespec64,

) -> libc::c_int;

);

if let Some(clock_gettime64) = __clock_gettime64.get() {

let mut t = MaybeUninit::uninit();

cvt(unsafe { clock_gettime64(clock, t.as_mut_ptr()) }).unwrap();

let t = unsafe { t.assume_init() };

return Timespec::new(t.tv_sec as i64, t.tv_nsec as i64).unwrap();

}

}

rustbot assigned tgross35 May 31, 2025

rustbot assigned cuviper and unassigned tgross35 May 31, 2025

dvdsk mentioned this pull request May 31, 2025

Specialize sleep_until implementation #118480

Closed

workingjubilee changed the title ~~Specialize sleep_until implementation for unix (expect mac)~~ Specialize sleep_until implementation for unix (except mac) May 31, 2025