use crate::cell::UnsafeCell; use crate::ptr; use crate::sync::atomic::{AtomicPtr, Ordering::Relaxed}; use crate::sys::locks::{pthread_mutex, Mutex}; use crate::sys::time::TIMESPEC_MAX; use crate::sys_common::lazy_box::{LazyBox, LazyInit}; use crate::time::Duration; struct AllocatedCondvar(UnsafeCell); pub struct Condvar { inner: LazyBox, mutex: AtomicPtr, } #[inline] fn raw(c: &Condvar) -> *mut libc::pthread_cond_t { c.inner.0.get() } unsafe impl Send for AllocatedCondvar {} unsafe impl Sync for AllocatedCondvar {} impl LazyInit for AllocatedCondvar { fn init() -> Box { let condvar = Box::new(AllocatedCondvar(UnsafeCell::new(libc::PTHREAD_COND_INITIALIZER))); cfg_if::cfg_if! { if #[cfg(any( target_os = "macos", target_os = "ios", target_os = "watchos", target_os = "l4re", target_os = "android", target_os = "redox" ))] { // `pthread_condattr_setclock` is unfortunately not supported on these platforms. } else if #[cfg(any(target_os = "espidf", target_os = "horizon"))] { // NOTE: ESP-IDF's PTHREAD_COND_INITIALIZER support is not released yet // So on that platform, init() should always be called // Moreover, that platform does not have pthread_condattr_setclock support, // hence that initialization should be skipped as well // // Similar story for the 3DS (horizon). let r = unsafe { libc::pthread_cond_init(condvar.0.get(), crate::ptr::null()) }; assert_eq!(r, 0); } else { use crate::mem::MaybeUninit; let mut attr = MaybeUninit::::uninit(); let r = unsafe { libc::pthread_condattr_init(attr.as_mut_ptr()) }; assert_eq!(r, 0); let r = unsafe { libc::pthread_condattr_setclock(attr.as_mut_ptr(), libc::CLOCK_MONOTONIC) }; assert_eq!(r, 0); let r = unsafe { libc::pthread_cond_init(condvar.0.get(), attr.as_ptr()) }; assert_eq!(r, 0); let r = unsafe { libc::pthread_condattr_destroy(attr.as_mut_ptr()) }; assert_eq!(r, 0); } } condvar } } impl Drop for AllocatedCondvar { #[inline] fn drop(&mut self) { let r = unsafe { libc::pthread_cond_destroy(self.0.get()) }; if cfg!(target_os = "dragonfly") { // 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); } else { debug_assert_eq!(r, 0); } } } impl Condvar { pub const fn new() -> Condvar { Condvar { inner: LazyBox::new(), mutex: AtomicPtr::new(ptr::null_mut()) } } #[inline] fn verify(&self, mutex: *mut libc::pthread_mutex_t) { // Relaxed is okay here because we never read through `self.addr`, and only use it to // compare addresses. match self.mutex.compare_exchange(ptr::null_mut(), mutex, Relaxed, Relaxed) { Ok(_) => {} // Stored the address Err(n) if n == mutex => {} // Lost a race to store the same address _ => panic!("attempted to use a condition variable with two mutexes"), } } #[inline] pub fn notify_one(&self) { let r = unsafe { libc::pthread_cond_signal(raw(self)) }; debug_assert_eq!(r, 0); } #[inline] pub fn notify_all(&self) { let r = unsafe { libc::pthread_cond_broadcast(raw(self)) }; debug_assert_eq!(r, 0); } #[inline] pub unsafe fn wait(&self, mutex: &Mutex) { let mutex = pthread_mutex::raw(mutex); self.verify(mutex); let r = libc::pthread_cond_wait(raw(self), 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 = "watchos", target_os = "android", target_os = "espidf", target_os = "horizon" )))] pub unsafe fn wait_timeout(&self, mutex: &Mutex, dur: Duration) -> bool { use crate::sys::time::Timespec; let mutex = pthread_mutex::raw(mutex); self.verify(mutex); let timeout = Timespec::now(libc::CLOCK_MONOTONIC) .checked_add_duration(&dur) .and_then(|t| t.to_timespec()) .unwrap_or(TIMESPEC_MAX); let r = libc::pthread_cond_timedwait(raw(self), 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 = "watchos", target_os = "android", target_os = "espidf", target_os = "horizon" ))] pub unsafe fn wait_timeout(&self, mutex: &Mutex, dur: Duration) -> bool { use crate::sys::time::SystemTime; use crate::time::Instant; let mutex = pthread_mutex::raw(mutex); self.verify(mutex); // 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 returns 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. let dur = Duration::min(dur, Duration::from_secs(1000 * 365 * 86400)); // pthread_cond_timedwait uses system time, but we want to report timeout // based on stable time. let now = Instant::now(); let timeout = SystemTime::now() .t .checked_add_duration(&dur) .and_then(|t| t.to_timespec()) .unwrap_or(TIMESPEC_MAX); let r = libc::pthread_cond_timedwait(raw(self), 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 now.elapsed() < dur } }