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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-17 12:02:58 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-17 12:02:58 +0000
commit698f8c2f01ea549d77d7dc3338a12e04c11057b9 (patch)
tree173a775858bd501c378080a10dca74132f05bc50 /library/std/src/sys/unix/futex.rs
parentInitial commit. (diff)
downloadrustc-698f8c2f01ea549d77d7dc3338a12e04c11057b9.tar.xz
rustc-698f8c2f01ea549d77d7dc3338a12e04c11057b9.zip
Adding upstream version 1.64.0+dfsg1.upstream/1.64.0+dfsg1
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'library/std/src/sys/unix/futex.rs')
-rw-r--r--library/std/src/sys/unix/futex.rs303
1 files changed, 303 insertions, 0 deletions
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<Duration>) -> 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::<u32>(), // 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<Duration>) -> 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<Duration>) -> 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<Duration>) -> 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<Duration>) -> 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) };
+}