| use crate::cell::UnsafeCell; |
| use crate::sys::mutex::{self, Mutex}; |
| use crate::time::Duration; |
| |
| pub struct Condvar { inner: UnsafeCell<libc::pthread_cond_t> } |
| |
| unsafe impl Send for Condvar {} |
| unsafe impl Sync for Condvar {} |
| |
| const TIMESPEC_MAX: libc::timespec = libc::timespec { |
| tv_sec: <libc::time_t>::max_value(), |
| tv_nsec: 1_000_000_000 - 1, |
| }; |
| |
| fn saturating_cast_to_time_t(value: u64) -> libc::time_t { |
| if value > <libc::time_t>::max_value() as u64 { |
| <libc::time_t>::max_value() |
| } else { |
| value as libc::time_t |
| } |
| } |
| |
| impl Condvar { |
| pub const fn new() -> Condvar { |
| // Might be moved and address is changing it is better to avoid |
| // initialization of potentially opaque OS data before it landed |
| Condvar { inner: UnsafeCell::new(libc::PTHREAD_COND_INITIALIZER) } |
| } |
| |
| #[cfg(any(target_os = "macos", |
| target_os = "ios", |
| target_os = "l4re", |
| target_os = "android", |
| target_os = "hermit", |
| target_os = "redox"))] |
| pub unsafe fn init(&mut self) {} |
| |
| #[cfg(not(any(target_os = "macos", |
| target_os = "ios", |
| target_os = "l4re", |
| target_os = "android", |
| target_os = "hermit", |
| target_os = "redox")))] |
| pub unsafe fn init(&mut self) { |
| use crate::mem::MaybeUninit; |
| let mut attr = MaybeUninit::<libc::pthread_condattr_t>::uninit(); |
| let r = libc::pthread_condattr_init(attr.as_mut_ptr()); |
| assert_eq!(r, 0); |
| let r = libc::pthread_condattr_setclock(attr.as_mut_ptr(), libc::CLOCK_MONOTONIC); |
| assert_eq!(r, 0); |
| let r = libc::pthread_cond_init(self.inner.get(), attr.as_ptr()); |
| assert_eq!(r, 0); |
| let r = libc::pthread_condattr_destroy(attr.as_mut_ptr()); |
| assert_eq!(r, 0); |
| } |
| |
| #[inline] |
| pub unsafe fn notify_one(&self) { |
| let r = libc::pthread_cond_signal(self.inner.get()); |
| debug_assert_eq!(r, 0); |
| } |
| |
| #[inline] |
| pub unsafe fn notify_all(&self) { |
| let r = libc::pthread_cond_broadcast(self.inner.get()); |
| debug_assert_eq!(r, 0); |
| } |
| |
| #[inline] |
| pub unsafe fn wait(&self, mutex: &Mutex) { |
| let r = libc::pthread_cond_wait(self.inner.get(), mutex::raw(mutex)); |
| debug_assert_eq!(r, 0); |
| } |
| |
| // This implementation is used on systems that support pthread_condattr_setclock |
| // where we configure condition variable to use monotonic clock (instead of |
| // default system clock). This approach avoids all problems that result |
| // from changes made to the system time. |
| #[cfg(not(any(target_os = "macos", |
| target_os = "ios", |
| target_os = "android", |
| target_os = "hermit")))] |
| pub unsafe fn wait_timeout(&self, mutex: &Mutex, dur: Duration) -> bool { |
| use crate::mem; |
| |
| let mut now: libc::timespec = mem::zeroed(); |
| let r = libc::clock_gettime(libc::CLOCK_MONOTONIC, &mut now); |
| assert_eq!(r, 0); |
| |
| // Nanosecond calculations can't overflow because both values are below 1e9. |
| let nsec = dur.subsec_nanos() + now.tv_nsec as u32; |
| |
| let sec = saturating_cast_to_time_t(dur.as_secs()) |
| .checked_add((nsec / 1_000_000_000) as libc::time_t) |
| .and_then(|s| s.checked_add(now.tv_sec)); |
| let nsec = nsec % 1_000_000_000; |
| |
| let timeout = sec.map(|s| { |
| libc::timespec { tv_sec: s, tv_nsec: nsec as _} |
| }).unwrap_or(TIMESPEC_MAX); |
| |
| let r = libc::pthread_cond_timedwait(self.inner.get(), mutex::raw(mutex), |
| &timeout); |
| assert!(r == libc::ETIMEDOUT || r == 0); |
| r == 0 |
| } |
| |
| |
| // This implementation is modeled after libcxx's condition_variable |
| // https://github.com/llvm-mirror/libcxx/blob/release_35/src/condition_variable.cpp#L46 |
| // https://github.com/llvm-mirror/libcxx/blob/release_35/include/__mutex_base#L367 |
| #[cfg(any(target_os = "macos", target_os = "ios", target_os = "android", target_os = "hermit"))] |
| pub unsafe fn wait_timeout(&self, mutex: &Mutex, mut dur: Duration) -> bool { |
| use crate::ptr; |
| use crate::time::Instant; |
| |
| // 1000 years |
| let max_dur = Duration::from_secs(1000 * 365 * 86400); |
| |
| if dur > max_dur { |
| // OSX implementation of `pthread_cond_timedwait` is buggy |
| // with super long durations. When duration is greater than |
| // 0x100_0000_0000_0000 seconds, `pthread_cond_timedwait` |
| // in macOS Sierra return error 316. |
| // |
| // This program demonstrates the issue: |
| // https://gist.github.com/stepancheg/198db4623a20aad2ad7cddb8fda4a63c |
| // |
| // To work around this issue, and possible bugs of other OSes, timeout |
| // is clamped to 1000 years, which is allowable per the API of `wait_timeout` |
| // because of spurious wakeups. |
| |
| dur = max_dur; |
| } |
| |
| // First, figure out what time it currently is, in both system and |
| // stable time. pthread_cond_timedwait uses system time, but we want to |
| // report timeout based on stable time. |
| let mut sys_now = libc::timeval { tv_sec: 0, tv_usec: 0 }; |
| let stable_now = Instant::now(); |
| let r = libc::gettimeofday(&mut sys_now, ptr::null_mut()); |
| debug_assert_eq!(r, 0); |
| |
| let nsec = dur.subsec_nanos() as libc::c_long + |
| (sys_now.tv_usec * 1000) as libc::c_long; |
| let extra = (nsec / 1_000_000_000) as libc::time_t; |
| let nsec = nsec % 1_000_000_000; |
| let seconds = saturating_cast_to_time_t(dur.as_secs()); |
| |
| let timeout = sys_now.tv_sec.checked_add(extra).and_then(|s| { |
| s.checked_add(seconds) |
| }).map(|s| { |
| libc::timespec { tv_sec: s, tv_nsec: nsec } |
| }).unwrap_or(TIMESPEC_MAX); |
| |
| // And wait! |
| let r = libc::pthread_cond_timedwait(self.inner.get(), mutex::raw(mutex), |
| &timeout); |
| debug_assert!(r == libc::ETIMEDOUT || r == 0); |
| |
| // ETIMEDOUT is not a totally reliable method of determining timeout due |
| // to clock shifts, so do the check ourselves |
| stable_now.elapsed() < dur |
| } |
| |
| #[inline] |
| #[cfg(not(target_os = "dragonfly"))] |
| pub unsafe fn destroy(&self) { |
| let r = libc::pthread_cond_destroy(self.inner.get()); |
| debug_assert_eq!(r, 0); |
| } |
| |
| #[inline] |
| #[cfg(target_os = "dragonfly")] |
| pub unsafe fn destroy(&self) { |
| let r = libc::pthread_cond_destroy(self.inner.get()); |
| // On DragonFly pthread_cond_destroy() returns EINVAL if called on |
| // a condvar that was just initialized with |
| // libc::PTHREAD_COND_INITIALIZER. Once it is used or |
| // pthread_cond_init() is called, this behaviour no longer occurs. |
| debug_assert!(r == 0 || r == libc::EINVAL); |
| } |
| } |