Auto merge of #96510 - m-ou-se:futex-bsd, r=Amanieu · rust-lang/rust@7f9e013 (original) (raw)

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`#![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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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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`))]

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`use crate::sync::atomic::AtomicU32;

`@@ -12,7 +15,7 @@ use crate::time::Duration;

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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"))]

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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) -> bool {

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`use super::time::Timespec;

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`use crate::ptr::null;

`@@ -30,18 +33,43 @@ pub fn futex_wait(futex: &AtomicU32, expected: u32, timeout: Option) -

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`return true;

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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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`let r = unsafe {

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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.t as *const libc::timespec),

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null::(), // 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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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.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::invalid_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.t as *const libc::timespec),

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null::(), // 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) {

`@@ -56,31 +84,133 @@ pub fn futex_wait(futex: &AtomicU32, expected: u32, timeout: Option) -

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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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+

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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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+

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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::syscall(

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libc::SYS_futex,

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futex as *const AtomicU32,

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libc::FUTEX_WAKE | libc::FUTEX_PRIVATE_FLAG,

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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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) > 0

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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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+

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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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+

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#[cfg(target_os = "openbsd")]

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pub fn futex_wait(futex: &AtomicU32, expected: u32, timeout: Option) -> bool {

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use crate::convert::TryInto;

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use crate::ptr::{null, null_mut};

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let timespec = timeout.and_then(|d| {

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Some(libc::timespec {

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// Sleep forever if the timeout is longer than fits in a timespec.

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tv_sec: d.as_secs().try_into().ok()?,

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// This conversion never truncates, as subsec_nanos is always <1e9.

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tv_nsec: d.subsec_nanos() as _,

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})

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});

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+

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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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+

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r == 0 || super::os::errno() != libc::ETIMEDOUT

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}

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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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/// 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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#[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::syscall(

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libc::SYS_futex,

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futex as *const AtomicU32,

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libc::FUTEX_WAKE | libc::FUTEX_PRIVATE_FLAG,

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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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#[cfg(target_os = "dragonfly")]

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pub fn futex_wait(futex: &AtomicU32, expected: u32, timeout: Option) -> bool {

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use crate::convert::TryFrom;

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+

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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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+

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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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+

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r == 0 || super::os::errno() != libc::ETIMEDOUT

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}

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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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+

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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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+

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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;