src/libstd/sys/unix/condvar.rs

   1 // Copyright 2014 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 use prelude::v1::*;
  12
  13 use cell::UnsafeCell;
  14 use libc;
  15 use ptr;
  16 use sys::mutex::{self, Mutex};
  17 use sys::time;
  18 use sys::sync as ffi;
  19 use time::Duration;
  20
  21 pub struct Condvar { inner: UnsafeCell<ffi::pthread_cond_t> }
  22
  23 unsafe impl Send for Condvar {}
  24 unsafe impl Sync for Condvar {}
  25
  26 pub const CONDVAR_INIT: Condvar = Condvar {
  27     inner: UnsafeCell { value: ffi::PTHREAD_COND_INITIALIZER },
  28 };
  29
  30 impl Condvar {
  31     #[inline]
  32     pub unsafe fn new() -> Condvar {
  33         // Might be moved and address is changing it is better to avoid
  34         // initialization of potentially opaque OS data before it landed
  35         Condvar { inner: UnsafeCell::new(ffi::PTHREAD_COND_INITIALIZER) }
  36     }
  37
  38     #[inline]
  39     pub unsafe fn notify_one(&self) {
  40         let r = ffi::pthread_cond_signal(self.inner.get());
  41         debug_assert_eq!(r, 0);
  42     }
  43
  44     #[inline]
  45     pub unsafe fn notify_all(&self) {
  46         let r = ffi::pthread_cond_broadcast(self.inner.get());
  47         debug_assert_eq!(r, 0);
  48     }
  49
  50     #[inline]
  51     pub unsafe fn wait(&self, mutex: &Mutex) {
  52         let r = ffi::pthread_cond_wait(self.inner.get(), mutex::raw(mutex));
  53         debug_assert_eq!(r, 0);
  54     }
  55
  56     // This implementation is modeled after libcxx's condition_variable
  57     // https://github.com/llvm-mirror/libcxx/blob/release_35/src/condition_variable.cpp#L46
  58     // https://github.com/llvm-mirror/libcxx/blob/release_35/include/__mutex_base#L367
  59     pub unsafe fn wait_timeout(&self, mutex: &Mutex, dur: Duration) -> bool {
  60         // First, figure out what time it currently is, in both system and
  61         // stable time.  pthread_cond_timedwait uses system time, but we want to
  62         // report timeout based on stable time.
  63         let mut sys_now = libc::timeval { tv_sec: 0, tv_usec: 0 };
  64         let stable_now = time::SteadyTime::now();
  65         let r = ffi::gettimeofday(&mut sys_now, ptr::null_mut());
  66         debug_assert_eq!(r, 0);
  67
  68         let seconds = dur.secs() as libc::time_t;
  69         let timeout = match sys_now.tv_sec.checked_add(seconds) {
  70             Some(sec) => {
  71                 libc::timespec {
  72                     tv_sec: sec,
  73                     tv_nsec: dur.extra_nanos() as libc::c_long,
  74                 }
  75             }
  76             None => {
  77                 libc::timespec {
  78                     tv_sec: <libc::time_t>::max_value(),
  79                     tv_nsec: 1_000_000_000 - 1,
  80                 }
  81             }
  82         };
  83
  84         // And wait!
  85         let r = ffi::pthread_cond_timedwait(self.inner.get(), mutex::raw(mutex),
  86                                             &timeout);
  87         debug_assert!(r == libc::ETIMEDOUT || r == 0);
  88
  89         // ETIMEDOUT is not a totally reliable method of determining timeout due
  90         // to clock shifts, so do the check ourselves
  91         &time::SteadyTime::now() - &stable_now < dur
  92     }
  93
  94     #[inline]
  95     #[cfg(not(target_os = "dragonfly"))]
  96     pub unsafe fn destroy(&self) {
  97         let r = ffi::pthread_cond_destroy(self.inner.get());
  98         debug_assert_eq!(r, 0);
  99     }
 100
 101     #[inline]
 102     #[cfg(target_os = "dragonfly")]
 103     pub unsafe fn destroy(&self) {
 104         let r = ffi::pthread_cond_destroy(self.inner.get());
 105         // On DragonFly pthread_cond_destroy() returns EINVAL if called on
 106         // a condvar that was just initialized with
 107         // ffi::PTHREAD_COND_INITIALIZER. Once it is used or
 108         // pthread_cond_init() is called, this behaviour no longer occurs.
 109         debug_assert!(r == 0 || r == libc::EINVAL);
 110     }
 111 }