From 698f8c2f01ea549d77d7dc3338a12e04c11057b9 Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Wed, 17 Apr 2024 14:02:58 +0200 Subject: Adding upstream version 1.64.0+dfsg1. Signed-off-by: Daniel Baumann --- library/std/src/sys/unix/futex.rs | 303 ++++++++++++++++++++++++++++++++++++++ 1 file changed, 303 insertions(+) create mode 100644 library/std/src/sys/unix/futex.rs (limited to 'library/std/src/sys/unix/futex.rs') diff --git a/library/std/src/sys/unix/futex.rs b/library/std/src/sys/unix/futex.rs new file mode 100644 index 000000000..8d5b54021 --- /dev/null +++ b/library/std/src/sys/unix/futex.rs @@ -0,0 +1,303 @@ +#![cfg(any( + target_os = "linux", + target_os = "android", + all(target_os = "emscripten", target_feature = "atomics"), + target_os = "freebsd", + target_os = "openbsd", + target_os = "dragonfly", + target_os = "fuchsia", +))] + +use crate::sync::atomic::AtomicU32; +use crate::time::Duration; + +/// Wait for a futex_wake operation to wake us. +/// +/// Returns directly if the futex doesn't hold the expected value. +/// +/// Returns false on timeout, and true in all other cases. +#[cfg(any(target_os = "linux", target_os = "android", target_os = "freebsd"))] +pub fn futex_wait(futex: &AtomicU32, expected: u32, timeout: Option) -> bool { + use super::time::Timespec; + use crate::ptr::null; + use crate::sync::atomic::Ordering::Relaxed; + + // Calculate the timeout as an absolute timespec. + // + // Overflows are rounded up to an infinite timeout (None). + let timespec = timeout + .and_then(|d| Timespec::now(libc::CLOCK_MONOTONIC).checked_add_duration(&d)) + .and_then(|t| t.to_timespec()); + + loop { + // No need to wait if the value already changed. + if futex.load(Relaxed) != expected { + return true; + } + + let r = unsafe { + cfg_if::cfg_if! { + if #[cfg(target_os = "freebsd")] { + // FreeBSD doesn't have futex(), but it has + // _umtx_op(UMTX_OP_WAIT_UINT_PRIVATE), which is nearly + // identical. It supports absolute timeouts through a flag + // in the _umtx_time struct. + let umtx_timeout = timespec.map(|t| libc::_umtx_time { + _timeout: t, + _flags: libc::UMTX_ABSTIME, + _clockid: libc::CLOCK_MONOTONIC as u32, + }); + let umtx_timeout_ptr = umtx_timeout.as_ref().map_or(null(), |t| t as *const _); + let umtx_timeout_size = umtx_timeout.as_ref().map_or(0, |t| crate::mem::size_of_val(t)); + libc::_umtx_op( + futex as *const AtomicU32 as *mut _, + libc::UMTX_OP_WAIT_UINT_PRIVATE, + expected as libc::c_ulong, + crate::ptr::invalid_mut(umtx_timeout_size), + umtx_timeout_ptr as *mut _, + ) + } else if #[cfg(any(target_os = "linux", target_os = "android"))] { + // 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, + futex as *const AtomicU32, + libc::FUTEX_WAIT_BITSET | libc::FUTEX_PRIVATE_FLAG, + expected, + timespec.as_ref().map_or(null(), |t| t as *const libc::timespec), + null::(), // This argument is unused for FUTEX_WAIT_BITSET. + !0u32, // A full bitmask, to make it behave like a regular FUTEX_WAIT. + ) + } else { + compile_error!("unknown target_os"); + } + } + }; + + match (r < 0).then(super::os::errno) { + Some(libc::ETIMEDOUT) => return false, + Some(libc::EINTR) => continue, + _ => return true, + } + } +} + +/// Wake up one thread that's blocked on futex_wait on this futex. +/// +/// Returns true if this actually woke up such a thread, +/// or false if no thread was waiting on this futex. +/// +/// On some platforms, this always returns false. +#[cfg(any(target_os = "linux", target_os = "android"))] +pub fn futex_wake(futex: &AtomicU32) -> bool { + let ptr = futex as *const AtomicU32; + let op = libc::FUTEX_WAKE | libc::FUTEX_PRIVATE_FLAG; + unsafe { libc::syscall(libc::SYS_futex, ptr, op, 1) > 0 } +} + +/// Wake up all threads that are waiting on futex_wait on this futex. +#[cfg(any(target_os = "linux", target_os = "android"))] +pub fn futex_wake_all(futex: &AtomicU32) { + let ptr = futex as *const AtomicU32; + let op = libc::FUTEX_WAKE | libc::FUTEX_PRIVATE_FLAG; + unsafe { + libc::syscall(libc::SYS_futex, ptr, op, i32::MAX); + } +} + +// FreeBSD doesn't tell us how many threads are woken up, so this always returns false. +#[cfg(target_os = "freebsd")] +pub fn futex_wake(futex: &AtomicU32) -> bool { + use crate::ptr::null_mut; + unsafe { + libc::_umtx_op( + futex as *const AtomicU32 as *mut _, + libc::UMTX_OP_WAKE_PRIVATE, + 1, + null_mut(), + null_mut(), + ) + }; + false +} + +#[cfg(target_os = "freebsd")] +pub fn futex_wake_all(futex: &AtomicU32) { + use crate::ptr::null_mut; + unsafe { + libc::_umtx_op( + futex as *const AtomicU32 as *mut _, + libc::UMTX_OP_WAKE_PRIVATE, + i32::MAX as libc::c_ulong, + null_mut(), + null_mut(), + ) + }; +} + +#[cfg(target_os = "openbsd")] +pub fn futex_wait(futex: &AtomicU32, expected: u32, timeout: Option) -> bool { + use super::time::Timespec; + use crate::ptr::{null, null_mut}; + + // Overflows are rounded up to an infinite timeout (None). + let timespec = timeout + .and_then(|d| Timespec::zero().checked_add_duration(&d)) + .and_then(|t| t.to_timespec()); + + let r = unsafe { + libc::futex( + futex as *const AtomicU32 as *mut u32, + libc::FUTEX_WAIT, + expected as i32, + timespec.as_ref().map_or(null(), |t| t as *const libc::timespec), + null_mut(), + ) + }; + + r == 0 || super::os::errno() != libc::ETIMEDOUT +} + +#[cfg(target_os = "openbsd")] +pub fn futex_wake(futex: &AtomicU32) -> bool { + use crate::ptr::{null, null_mut}; + unsafe { + libc::futex(futex as *const AtomicU32 as *mut u32, libc::FUTEX_WAKE, 1, null(), null_mut()) + > 0 + } +} + +#[cfg(target_os = "openbsd")] +pub fn futex_wake_all(futex: &AtomicU32) { + use crate::ptr::{null, null_mut}; + unsafe { + libc::futex( + futex as *const AtomicU32 as *mut u32, + libc::FUTEX_WAKE, + i32::MAX, + null(), + null_mut(), + ); + } +} + +#[cfg(target_os = "dragonfly")] +pub fn futex_wait(futex: &AtomicU32, expected: u32, timeout: Option) -> bool { + // A timeout of 0 means infinite. + // We round smaller timeouts up to 1 millisecond. + // Overflows are rounded up to an infinite timeout. + let timeout_ms = + timeout.and_then(|d| Some(i32::try_from(d.as_millis()).ok()?.max(1))).unwrap_or(0); + + let r = unsafe { + libc::umtx_sleep(futex as *const AtomicU32 as *const i32, expected as i32, timeout_ms) + }; + + r == 0 || super::os::errno() != libc::ETIMEDOUT +} + +// DragonflyBSD doesn't tell us how many threads are woken up, so this always returns false. +#[cfg(target_os = "dragonfly")] +pub fn futex_wake(futex: &AtomicU32) -> bool { + unsafe { libc::umtx_wakeup(futex as *const AtomicU32 as *const i32, 1) }; + false +} + +#[cfg(target_os = "dragonfly")] +pub fn futex_wake_all(futex: &AtomicU32) { + unsafe { libc::umtx_wakeup(futex as *const AtomicU32 as *const i32, i32::MAX) }; +} + +#[cfg(target_os = "emscripten")] +extern "C" { + fn emscripten_futex_wake(addr: *const AtomicU32, count: libc::c_int) -> libc::c_int; + fn emscripten_futex_wait( + addr: *const AtomicU32, + val: libc::c_uint, + max_wait_ms: libc::c_double, + ) -> libc::c_int; +} + +#[cfg(target_os = "emscripten")] +pub fn futex_wait(futex: &AtomicU32, expected: u32, timeout: Option) -> bool { + unsafe { + emscripten_futex_wait( + futex, + expected, + timeout.map_or(f64::INFINITY, |d| d.as_secs_f64() * 1000.0), + ) != -libc::ETIMEDOUT + } +} + +#[cfg(target_os = "emscripten")] +pub fn futex_wake(futex: &AtomicU32) -> bool { + unsafe { emscripten_futex_wake(futex, 1) > 0 } +} + +#[cfg(target_os = "emscripten")] +pub fn futex_wake_all(futex: &AtomicU32) { + unsafe { emscripten_futex_wake(futex, i32::MAX) }; +} + +#[cfg(target_os = "fuchsia")] +pub mod zircon { + pub type zx_futex_t = crate::sync::atomic::AtomicU32; + pub type zx_handle_t = u32; + pub type zx_status_t = i32; + pub type zx_time_t = i64; + + pub const ZX_HANDLE_INVALID: zx_handle_t = 0; + + pub const ZX_TIME_INFINITE: zx_time_t = zx_time_t::MAX; + + pub const ZX_OK: zx_status_t = 0; + pub const ZX_ERR_INVALID_ARGS: zx_status_t = -10; + pub const ZX_ERR_BAD_HANDLE: zx_status_t = -11; + pub const ZX_ERR_WRONG_TYPE: zx_status_t = -12; + pub const ZX_ERR_BAD_STATE: zx_status_t = -20; + pub const ZX_ERR_TIMED_OUT: zx_status_t = -21; + + extern "C" { + pub fn zx_clock_get_monotonic() -> zx_time_t; + pub fn zx_futex_wait( + value_ptr: *const zx_futex_t, + current_value: zx_futex_t, + new_futex_owner: zx_handle_t, + deadline: zx_time_t, + ) -> zx_status_t; + pub fn zx_futex_wake(value_ptr: *const zx_futex_t, wake_count: u32) -> zx_status_t; + pub fn zx_futex_wake_single_owner(value_ptr: *const zx_futex_t) -> zx_status_t; + pub fn zx_thread_self() -> zx_handle_t; + } +} + +#[cfg(target_os = "fuchsia")] +pub fn futex_wait(futex: &AtomicU32, expected: u32, timeout: Option) -> bool { + use crate::convert::TryFrom; + + // Sleep forever if the timeout is longer than fits in a i64. + let deadline = timeout + .and_then(|d| { + i64::try_from(d.as_nanos()) + .ok()? + .checked_add(unsafe { zircon::zx_clock_get_monotonic() }) + }) + .unwrap_or(zircon::ZX_TIME_INFINITE); + + unsafe { + zircon::zx_futex_wait(futex, AtomicU32::new(expected), zircon::ZX_HANDLE_INVALID, deadline) + != zircon::ZX_ERR_TIMED_OUT + } +} + +// Fuchsia doesn't tell us how many threads are woken up, so this always returns false. +#[cfg(target_os = "fuchsia")] +pub fn futex_wake(futex: &AtomicU32) -> bool { + unsafe { zircon::zx_futex_wake(futex, 1) }; + false +} + +#[cfg(target_os = "fuchsia")] +pub fn futex_wake_all(futex: &AtomicU32) { + unsafe { zircon::zx_futex_wake(futex, u32::MAX) }; +} -- cgit v1.2.3