library/std/src/sys/unix/futex.rs

   1 #![cfg(any(
   2     target_os = "linux",
   3     target_os = "android",
   4     all(target_os = "emscripten", target_feature = "atomics")
   5 ))]
   6
   7 #[cfg(any(target_os = "linux", target_os = "android"))]
   8 use crate::convert::TryInto;
   9 #[cfg(any(target_os = "linux", target_os = "android"))]
  10 use crate::ptr::null;
  11 use crate::sync::atomic::AtomicI32;
  12 use crate::time::Duration;
  13
  14 #[cfg(any(target_os = "linux", target_os = "android"))]
  15 pub fn futex_wait(futex: &AtomicI32, expected: i32, timeout: Option<Duration>) {
  16     let timespec = timeout.and_then(|d| {
  17         Some(libc::timespec {
  18             // Sleep forever if the timeout is longer than fits in a timespec.
  19             tv_sec: d.as_secs().try_into().ok()?,
  20             // This conversion never truncates, as subsec_nanos is always <1e9.
  21             tv_nsec: d.subsec_nanos() as _,
  22         })
  23     });
  24     unsafe {
  25         libc::syscall(
  26             libc::SYS_futex,
  27             futex as *const AtomicI32,
  28             libc::FUTEX_WAIT | libc::FUTEX_PRIVATE_FLAG,
  29             expected,
  30             timespec.as_ref().map_or(null(), |d| d as *const libc::timespec),
  31         );
  32     }
  33 }
  34
  35 #[cfg(target_os = "emscripten")]
  36 pub fn futex_wait(futex: &AtomicI32, expected: i32, timeout: Option<Duration>) {
  37     extern "C" {
  38         fn emscripten_futex_wait(
  39             addr: *const AtomicI32,
  40             val: libc::c_uint,
  41             max_wait_ms: libc::c_double,
  42         ) -> libc::c_int;
  43     }
  44
  45     unsafe {
  46         emscripten_futex_wait(
  47             futex as *const AtomicI32,
  48             // `val` is declared unsigned to match the Emscripten headers, but since it's used as
  49             // an opaque value, we can ignore the meaning of signed vs. unsigned and cast here.
  50             expected as libc::c_uint,
  51             timeout.map_or(crate::f64::INFINITY, |d| d.as_secs_f64() * 1000.0),
  52         );
  53     }
  54 }
  55
  56 #[cfg(any(target_os = "linux", target_os = "android"))]
  57 pub fn futex_wake(futex: &AtomicI32) {
  58     unsafe {
  59         libc::syscall(
  60             libc::SYS_futex,
  61             futex as *const AtomicI32,
  62             libc::FUTEX_WAKE | libc::FUTEX_PRIVATE_FLAG,
  63             1,
  64         );
  65     }
  66 }
  67
  68 #[cfg(target_os = "emscripten")]
  69 pub fn futex_wake(futex: &AtomicI32) {
  70     extern "C" {
  71         fn emscripten_futex_wake(addr: *const AtomicI32, count: libc::c_int) -> libc::c_int;
  72     }
  73
  74     unsafe {
  75         emscripten_futex_wake(futex as *const AtomicI32, 1);
  76     }
  77 }