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Use 64-bit futex syscalls on RV32 Linux #164748

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Merged
rust-bors merged 2 commits into from
Oct 24, 2026
Merged

Use 64-bit futex syscalls on RV32 Linux #164748

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c860e0d
Use 64-bit time for futex syscalls on RV32
TechnoPorg Oct 21, 2026
093a6f1
fix: update rustix to version compatible with latest libc
TechnoPorg Oct 23, 2026
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12 changes: 6 additions & 6 deletions Cargo.lock
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Original file line number Diff line number Diff line change
Expand Up @@ -2273,9 +2273,9 @@ checksum = "803ec87c9cfb29b9d2633f20cba1f488db3fd53f2158b1024cbefb47ba05d413"

[[package]]
name = "libc"
version = "0.2.189"
version = "0.2.191"
source = "registry+https://github.com/rust-lang/crates.io-index"
checksum = "3eaf3ede3fee6db1a4c2ee091bf8a8b4dccdc6d17f656fb07896ee72867612f2"
checksum = "65cd87c9a6d60536580b316ad985726104730a5151c99845f2490428ef91240a"

[[package]]
name = "libffi"
Expand Down Expand Up @@ -2378,9 +2378,9 @@ dependencies = [

[[package]]
name = "linux-raw-sys"
version = "0.11.0"
version = "0.12.1"
source = "registry+https://github.com/rust-lang/crates.io-index"
checksum = "df1d3c3b53da64cf5760482273a98e575c651a67eec7f77df96b5b642de8f039"
checksum = "32a66949e030da00e8c7d4434b251670a91556f4144941d37452769c25d58a53"

[[package]]
name = "litemap"
Expand Down Expand Up @@ -5191,9 +5191,9 @@ dependencies = [

[[package]]
name = "rustix"
version = "1.1.2"
version = "1.1.5"
source = "registry+https://github.com/rust-lang/crates.io-index"
checksum = "cd15f8a2c5551a84d56efdc1cd049089e409ac19a3072d5037a17fd70719ff3e"
checksum = "891efababe418670775f199f0d233d84843c227a0949a883ce15b37c78d6629d"
dependencies = [
"bitflags",
"errno",
Expand Down
18 changes: 15 additions & 3 deletions library/std/src/sys/sync/futex/unix.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -11,6 +11,18 @@ pub type SmallFutex = Atomic<SmallPrimitive>;
/// Must be the underlying type of SmallFutex
pub type SmallPrimitive = u32;

#[cfg(any(target_os = "linux", target_os = "android"))]
cfg_select! {
// riscv32 only exposes the `SYS_futex_time64` syscall,
// whereas other 32-bit targets also expose `SYS_futex`, which uses 32-bit time.
target_arch = "riscv32" => {
use libc::SYS_futex_time64 as SYS_futex;
}
_ => {
use libc::SYS_futex;
}
}

/// Waits for a `futex_wake` operation to wake us.
///
/// Returns directly if the futex doesn't hold the expected value.
Expand Down Expand Up @@ -61,7 +73,7 @@ pub fn futex_wait(futex: &Atomic<u32>, expected: u32, timeout: Option<Duration>)
// Use FUTEX_WAIT_BITSET rather than FUTEX_WAIT to be able to give an
// absolute time rather than a relative time.
libc::syscall(
libc::SYS_futex,
SYS_futex,
futex as *const Atomic<u32> as *const u32,
libc::FUTEX_WAIT_BITSET | libc::FUTEX_PRIVATE_FLAG,
expected,
Expand Down Expand Up @@ -94,7 +106,7 @@ pub fn futex_wait(futex: &Atomic<u32>, expected: u32, timeout: Option<Duration>)
pub fn futex_wake(futex: &Atomic<u32>) -> bool {
let ptr = futex as *const Atomic<u32> as *const u32;
let op = libc::FUTEX_WAKE | libc::FUTEX_PRIVATE_FLAG;
unsafe { libc::syscall(libc::SYS_futex, ptr, op, 1) > 0 }
unsafe { libc::syscall(SYS_futex, ptr, op, 1) > 0 }
}

/// Wakes up all threads that are waiting on `futex_wait` on this futex.
Expand All @@ -103,7 +115,7 @@ pub fn futex_wake_all(futex: &Atomic<u32>) {
let ptr = futex as *const Atomic<u32> as *const u32;
let op = libc::FUTEX_WAKE | libc::FUTEX_PRIVATE_FLAG;
unsafe {
libc::syscall(libc::SYS_futex, ptr, op, i32::MAX);
libc::syscall(SYS_futex, ptr, op, i32::MAX);
}
}

Expand Down
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