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