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use crate::fmt; use crate::sync::atomic::{AtomicUsize, Ordering}; use crate::sync::{mutex, MutexGuard, PoisonError}; use crate::sys_common::condvar as sys; use crate::sys_common::mutex as sys_mutex; use crate::sys_common::poison::{self, LockResult}; use crate::time::{Duration, Instant}; /// A type indicating whether a timed wait on a condition variable returned /// due to a time out or not. /// /// It is returned by the [`wait_timeout`] method. /// /// [`wait_timeout`]: struct.Condvar.html#method.wait_timeout #[derive(Debug, PartialEq, Eq, Copy, Clone)] #[stable(feature = "wait_timeout", since = "1.5.0")] pub struct WaitTimeoutResult(bool); impl WaitTimeoutResult { /// Returns `true` if the wait was known to have timed out. /// /// # Examples /// /// This example spawns a thread which will update the boolean value and /// then wait 100 milliseconds before notifying the condvar. /// /// The main thread will wait with a timeout on the condvar and then leave /// once the boolean has been updated and notified. /// /// ``` /// use std::sync::{Arc, Condvar, Mutex}; /// use std::thread; /// use std::time::Duration; /// /// let pair = Arc::new((Mutex::new(false), Condvar::new())); /// let pair2 = pair.clone(); /// /// thread::spawn(move || { /// let (lock, cvar) = &*pair2; /// /// // Let's wait 20 milliseconds before notifying the condvar. /// thread::sleep(Duration::from_millis(20)); /// /// let mut started = lock.lock().unwrap(); /// // We update the boolean value. /// *started = true; /// cvar.notify_one(); /// }); /// /// // Wait for the thread to start up. /// let (lock, cvar) = &*pair; /// let mut started = lock.lock().unwrap(); /// loop { /// // Let's put a timeout on the condvar's wait. /// let result = cvar.wait_timeout(started, Duration::from_millis(10)).unwrap(); /// // 10 milliseconds have passed, or maybe the value changed! /// started = result.0; /// if *started == true { /// // We received the notification and the value has been updated, we can leave. /// break /// } /// } /// ``` #[stable(feature = "wait_timeout", since = "1.5.0")] pub fn timed_out(&self) -> bool { self.0 } } /// A Condition Variable /// /// Condition variables represent the ability to block a thread such that it /// consumes no CPU time while waiting for an event to occur. Condition /// variables are typically associated with a boolean predicate (a condition) /// and a mutex. The predicate is always verified inside of the mutex before /// determining that a thread must block. /// /// Functions in this module will block the current **thread** of execution and /// are bindings to system-provided condition variables where possible. Note /// that this module places one additional restriction over the system condition /// variables: each condvar can be used with precisely one mutex at runtime. Any /// attempt to use multiple mutexes on the same condition variable will result /// in a runtime panic. If this is not desired, then the unsafe primitives in /// `sys` do not have this restriction but may result in undefined behavior. /// /// # Examples /// /// ``` /// use std::sync::{Arc, Mutex, Condvar}; /// use std::thread; /// /// let pair = Arc::new((Mutex::new(false), Condvar::new())); /// let pair2 = pair.clone(); /// /// // Inside of our lock, spawn a new thread, and then wait for it to start. /// thread::spawn(move|| { /// let (lock, cvar) = &*pair2; /// let mut started = lock.lock().unwrap(); /// *started = true; /// // We notify the condvar that the value has changed. /// cvar.notify_one(); /// }); /// /// // Wait for the thread to start up. /// let (lock, cvar) = &*pair; /// let mut started = lock.lock().unwrap(); /// while !*started { /// started = cvar.wait(started).unwrap(); /// } /// ``` #[stable(feature = "rust1", since = "1.0.0")] pub struct Condvar { inner: Box<sys::Condvar>, mutex: AtomicUsize, } impl Condvar { /// Creates a new condition variable which is ready to be waited on and /// notified. /// /// # Examples /// /// ``` /// use std::sync::Condvar; /// /// let condvar = Condvar::new(); /// ``` #[stable(feature = "rust1", since = "1.0.0")] pub fn new() -> Condvar { let mut c = Condvar { inner: box sys::Condvar::new(), mutex: AtomicUsize::new(0), }; unsafe { c.inner.init(); } c } /// Blocks the current thread until this condition variable receives a /// notification. /// /// This function will atomically unlock the mutex specified (represented by /// `guard`) and block the current thread. This means that any calls /// to [`notify_one`] or [`notify_all`] which happen logically after the /// mutex is unlocked are candidates to wake this thread up. When this /// function call returns, the lock specified will have been re-acquired. /// /// Note that this function is susceptible to spurious wakeups. Condition /// variables normally have a boolean predicate associated with them, and /// the predicate must always be checked each time this function returns to /// protect against spurious wakeups. /// /// # Errors /// /// This function will return an error if the mutex being waited on is /// poisoned when this thread re-acquires the lock. For more information, /// see information about [poisoning] on the [`Mutex`] type. /// /// # Panics /// /// This function will [`panic!`] if it is used with more than one mutex /// over time. Each condition variable is dynamically bound to exactly one /// mutex to ensure defined behavior across platforms. If this functionality /// is not desired, then unsafe primitives in `sys` are provided. /// /// [`notify_one`]: #method.notify_one /// [`notify_all`]: #method.notify_all /// [poisoning]: ../sync/struct.Mutex.html#poisoning /// [`Mutex`]: ../sync/struct.Mutex.html /// [`panic!`]: ../../std/macro.panic.html /// /// # Examples /// /// ``` /// use std::sync::{Arc, Mutex, Condvar}; /// use std::thread; /// /// let pair = Arc::new((Mutex::new(false), Condvar::new())); /// let pair2 = pair.clone(); /// /// thread::spawn(move|| { /// let (lock, cvar) = &*pair2; /// let mut started = lock.lock().unwrap(); /// *started = true; /// // We notify the condvar that the value has changed. /// cvar.notify_one(); /// }); /// /// // Wait for the thread to start up. /// let (lock, cvar) = &*pair; /// let mut started = lock.lock().unwrap(); /// // As long as the value inside the `Mutex<bool>` is `false`, we wait. /// while !*started { /// started = cvar.wait(started).unwrap(); /// } /// ``` #[stable(feature = "rust1", since = "1.0.0")] pub fn wait<'a, T>(&self, guard: MutexGuard<'a, T>) -> LockResult<MutexGuard<'a, T>> { let poisoned = unsafe { let lock = mutex::guard_lock(&guard); self.verify(lock); self.inner.wait(lock); mutex::guard_poison(&guard).get() }; if poisoned { Err(PoisonError::new(guard)) } else { Ok(guard) } } /// Blocks the current thread until this condition variable receives a /// notification and the required condition is met. Spurious wakeups are /// ignored and this function will only return once the condition has been /// met. /// /// This function will atomically unlock the mutex specified (represented by /// `guard`) and block the current thread. This means that any calls /// to [`notify_one`] or [`notify_all`] which happen logically after the /// mutex is unlocked are candidates to wake this thread up. When this /// function call returns, the lock specified will have been re-acquired. /// /// # Errors /// /// This function will return an error if the mutex being waited on is /// poisoned when this thread re-acquires the lock. For more information, /// see information about [poisoning] on the [`Mutex`] type. /// /// [`notify_one`]: #method.notify_one /// [`notify_all`]: #method.notify_all /// [poisoning]: ../sync/struct.Mutex.html#poisoning /// [`Mutex`]: ../sync/struct.Mutex.html /// /// # Examples /// /// ``` /// #![feature(wait_until)] /// /// use std::sync::{Arc, Mutex, Condvar}; /// use std::thread; /// /// let pair = Arc::new((Mutex::new(false), Condvar::new())); /// let pair2 = pair.clone(); /// /// thread::spawn(move|| { /// let (lock, cvar) = &*pair2; /// let mut started = lock.lock().unwrap(); /// *started = true; /// // We notify the condvar that the value has changed. /// cvar.notify_one(); /// }); /// /// // Wait for the thread to start up. /// let (lock, cvar) = &*pair; /// // As long as the value inside the `Mutex<bool>` is `false`, we wait. /// let _guard = cvar.wait_until(lock.lock().unwrap(), |started| { *started }).unwrap(); /// ``` #[unstable(feature = "wait_until", issue = "47960")] pub fn wait_until<'a, T, F>(&self, mut guard: MutexGuard<'a, T>, mut condition: F) -> LockResult<MutexGuard<'a, T>> where F: FnMut(&mut T) -> bool { while !condition(&mut *guard) { guard = self.wait(guard)?; } Ok(guard) } /// Waits on this condition variable for a notification, timing out after a /// specified duration. /// /// The semantics of this function are equivalent to [`wait`] /// except that the thread will be blocked for roughly no longer /// than `ms` milliseconds. This method should not be used for /// precise timing due to anomalies such as preemption or platform /// differences that may not cause the maximum amount of time /// waited to be precisely `ms`. /// /// Note that the best effort is made to ensure that the time waited is /// measured with a monotonic clock, and not affected by the changes made to /// the system time. /// /// The returned boolean is `false` only if the timeout is known /// to have elapsed. /// /// Like [`wait`], the lock specified will be re-acquired when this function /// returns, regardless of whether the timeout elapsed or not. /// /// [`wait`]: #method.wait /// /// # Examples /// /// ``` /// use std::sync::{Arc, Mutex, Condvar}; /// use std::thread; /// /// let pair = Arc::new((Mutex::new(false), Condvar::new())); /// let pair2 = pair.clone(); /// /// thread::spawn(move|| { /// let (lock, cvar) = &*pair2; /// let mut started = lock.lock().unwrap(); /// *started = true; /// // We notify the condvar that the value has changed. /// cvar.notify_one(); /// }); /// /// // Wait for the thread to start up. /// let (lock, cvar) = &*pair; /// let mut started = lock.lock().unwrap(); /// // As long as the value inside the `Mutex<bool>` is `false`, we wait. /// loop { /// let result = cvar.wait_timeout_ms(started, 10).unwrap(); /// // 10 milliseconds have passed, or maybe the value changed! /// started = result.0; /// if *started == true { /// // We received the notification and the value has been updated, we can leave. /// break /// } /// } /// ``` #[stable(feature = "rust1", since = "1.0.0")] #[rustc_deprecated(since = "1.6.0", reason = "replaced by `std::sync::Condvar::wait_timeout`")] pub fn wait_timeout_ms<'a, T>(&self, guard: MutexGuard<'a, T>, ms: u32) -> LockResult<(MutexGuard<'a, T>, bool)> { let res = self.wait_timeout(guard, Duration::from_millis(ms as u64)); poison::map_result(res, |(a, b)| { (a, !b.timed_out()) }) } /// Waits on this condition variable for a notification, timing out after a /// specified duration. /// /// The semantics of this function are equivalent to [`wait`] except that /// the thread will be blocked for roughly no longer than `dur`. This /// method should not be used for precise timing due to anomalies such as /// preemption or platform differences that may not cause the maximum /// amount of time waited to be precisely `dur`. /// /// Note that the best effort is made to ensure that the time waited is /// measured with a monotonic clock, and not affected by the changes made to /// the system time. This function is susceptible to spurious wakeups. /// Condition variables normally have a boolean predicate associated with /// them, and the predicate must always be checked each time this function /// returns to protect against spurious wakeups. Additionally, it is /// typically desirable for the time-out to not exceed some duration in /// spite of spurious wakes, thus the sleep-duration is decremented by the /// amount slept. Alternatively, use the `wait_timeout_until` method /// to wait until a condition is met with a total time-out regardless /// of spurious wakes. /// /// The returned [`WaitTimeoutResult`] value indicates if the timeout is /// known to have elapsed. /// /// Like [`wait`], the lock specified will be re-acquired when this function /// returns, regardless of whether the timeout elapsed or not. /// /// [`wait`]: #method.wait /// [`wait_timeout_until`]: #method.wait_timeout_until /// [`WaitTimeoutResult`]: struct.WaitTimeoutResult.html /// /// # Examples /// /// ``` /// use std::sync::{Arc, Mutex, Condvar}; /// use std::thread; /// use std::time::Duration; /// /// let pair = Arc::new((Mutex::new(false), Condvar::new())); /// let pair2 = pair.clone(); /// /// thread::spawn(move|| { /// let (lock, cvar) = &*pair2; /// let mut started = lock.lock().unwrap(); /// *started = true; /// // We notify the condvar that the value has changed. /// cvar.notify_one(); /// }); /// /// // wait for the thread to start up /// let (lock, cvar) = &*pair; /// let mut started = lock.lock().unwrap(); /// // as long as the value inside the `Mutex<bool>` is `false`, we wait /// loop { /// let result = cvar.wait_timeout(started, Duration::from_millis(10)).unwrap(); /// // 10 milliseconds have passed, or maybe the value changed! /// started = result.0; /// if *started == true { /// // We received the notification and the value has been updated, we can leave. /// break /// } /// } /// ``` #[stable(feature = "wait_timeout", since = "1.5.0")] pub fn wait_timeout<'a, T>(&self, guard: MutexGuard<'a, T>, dur: Duration) -> LockResult<(MutexGuard<'a, T>, WaitTimeoutResult)> { let (poisoned, result) = unsafe { let lock = mutex::guard_lock(&guard); self.verify(lock); let success = self.inner.wait_timeout(lock, dur); (mutex::guard_poison(&guard).get(), WaitTimeoutResult(!success)) }; if poisoned { Err(PoisonError::new((guard, result))) } else { Ok((guard, result)) } } /// Waits on this condition variable for a notification, timing out after a /// specified duration. Spurious wakes will not cause this function to /// return. /// /// The semantics of this function are equivalent to [`wait_until`] except /// that the thread will be blocked for roughly no longer than `dur`. This /// method should not be used for precise timing due to anomalies such as /// preemption or platform differences that may not cause the maximum /// amount of time waited to be precisely `dur`. /// /// Note that the best effort is made to ensure that the time waited is /// measured with a monotonic clock, and not affected by the changes made to /// the system time. /// /// The returned [`WaitTimeoutResult`] value indicates if the timeout is /// known to have elapsed without the condition being met. /// /// Like [`wait_until`], the lock specified will be re-acquired when this /// function returns, regardless of whether the timeout elapsed or not. /// /// [`wait_until`]: #method.wait_until /// [`wait_timeout`]: #method.wait_timeout /// [`WaitTimeoutResult`]: struct.WaitTimeoutResult.html /// /// # Examples /// /// ``` /// #![feature(wait_timeout_until)] /// /// use std::sync::{Arc, Mutex, Condvar}; /// use std::thread; /// use std::time::Duration; /// /// let pair = Arc::new((Mutex::new(false), Condvar::new())); /// let pair2 = pair.clone(); /// /// thread::spawn(move|| { /// let (lock, cvar) = &*pair2; /// let mut started = lock.lock().unwrap(); /// *started = true; /// // We notify the condvar that the value has changed. /// cvar.notify_one(); /// }); /// /// // wait for the thread to start up /// let (lock, cvar) = &*pair; /// let result = cvar.wait_timeout_until( /// lock.lock().unwrap(), /// Duration::from_millis(100), /// |&mut started| started, /// ).unwrap(); /// if result.1.timed_out() { /// // timed-out without the condition ever evaluating to true. /// } /// // access the locked mutex via result.0 /// ``` #[unstable(feature = "wait_timeout_until", issue = "47960")] pub fn wait_timeout_until<'a, T, F>(&self, mut guard: MutexGuard<'a, T>, dur: Duration, mut condition: F) -> LockResult<(MutexGuard<'a, T>, WaitTimeoutResult)> where F: FnMut(&mut T) -> bool { let start = Instant::now(); loop { if condition(&mut *guard) { return Ok((guard, WaitTimeoutResult(false))); } let timeout = match dur.checked_sub(start.elapsed()) { Some(timeout) => timeout, None => return Ok((guard, WaitTimeoutResult(true))), }; guard = self.wait_timeout(guard, timeout)?.0; } } /// Wakes up one blocked thread on this condvar. /// /// If there is a blocked thread on this condition variable, then it will /// be woken up from its call to [`wait`] or [`wait_timeout`]. Calls to /// `notify_one` are not buffered in any way. /// /// To wake up all threads, see [`notify_all`]. /// /// [`wait`]: #method.wait /// [`wait_timeout`]: #method.wait_timeout /// [`notify_all`]: #method.notify_all /// /// # Examples /// /// ``` /// use std::sync::{Arc, Mutex, Condvar}; /// use std::thread; /// /// let pair = Arc::new((Mutex::new(false), Condvar::new())); /// let pair2 = pair.clone(); /// /// thread::spawn(move|| { /// let (lock, cvar) = &*pair2; /// let mut started = lock.lock().unwrap(); /// *started = true; /// // We notify the condvar that the value has changed. /// cvar.notify_one(); /// }); /// /// // Wait for the thread to start up. /// let (lock, cvar) = &*pair; /// let mut started = lock.lock().unwrap(); /// // As long as the value inside the `Mutex<bool>` is `false`, we wait. /// while !*started { /// started = cvar.wait(started).unwrap(); /// } /// ``` #[stable(feature = "rust1", since = "1.0.0")] pub fn notify_one(&self) { unsafe { self.inner.notify_one() } } /// Wakes up all blocked threads on this condvar. /// /// This method will ensure that any current waiters on the condition /// variable are awoken. Calls to `notify_all()` are not buffered in any /// way. /// /// To wake up only one thread, see [`notify_one`]. /// /// [`notify_one`]: #method.notify_one /// /// # Examples /// /// ``` /// use std::sync::{Arc, Mutex, Condvar}; /// use std::thread; /// /// let pair = Arc::new((Mutex::new(false), Condvar::new())); /// let pair2 = pair.clone(); /// /// thread::spawn(move|| { /// let (lock, cvar) = &*pair2; /// let mut started = lock.lock().unwrap(); /// *started = true; /// // We notify the condvar that the value has changed. /// cvar.notify_all(); /// }); /// /// // Wait for the thread to start up. /// let (lock, cvar) = &*pair; /// let mut started = lock.lock().unwrap(); /// // As long as the value inside the `Mutex<bool>` is `false`, we wait. /// while !*started { /// started = cvar.wait(started).unwrap(); /// } /// ``` #[stable(feature = "rust1", since = "1.0.0")] pub fn notify_all(&self) { unsafe { self.inner.notify_all() } } fn verify(&self, mutex: &sys_mutex::Mutex) { let addr = mutex as *const _ as usize; match self.mutex.compare_and_swap(0, addr, Ordering::SeqCst) { // If we got out 0, then we have successfully bound the mutex to // this cvar. 0 => {} // If we get out a value that's the same as `addr`, then someone // already beat us to the punch. n if n == addr => {} // Anything else and we're using more than one mutex on this cvar, // which is currently disallowed. _ => panic!("attempted to use a condition variable with two \ mutexes"), } } } #[stable(feature = "std_debug", since = "1.16.0")] impl fmt::Debug for Condvar { fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { f.pad("Condvar { .. }") } } #[stable(feature = "condvar_default", since = "1.10.0")] impl Default for Condvar { /// Creates a `Condvar` which is ready to be waited on and notified. fn default() -> Condvar { Condvar::new() } } #[stable(feature = "rust1", since = "1.0.0")] impl Drop for Condvar { fn drop(&mut self) { unsafe { self.inner.destroy() } } } #[cfg(test)] mod tests { /// #![feature(wait_until)] use crate::sync::mpsc::channel; use crate::sync::{Condvar, Mutex, Arc}; use crate::sync::atomic::{AtomicBool, Ordering}; use crate::thread; use crate::time::Duration; use crate::u64; #[test] fn smoke() { let c = Condvar::new(); c.notify_one(); c.notify_all(); } #[test] #[cfg_attr(target_os = "emscripten", ignore)] fn notify_one() { let m = Arc::new(Mutex::new(())); let m2 = m.clone(); let c = Arc::new(Condvar::new()); let c2 = c.clone(); let g = m.lock().unwrap(); let _t = thread::spawn(move|| { let _g = m2.lock().unwrap(); c2.notify_one(); }); let g = c.wait(g).unwrap(); drop(g); } #[test] #[cfg_attr(target_os = "emscripten", ignore)] fn notify_all() { const N: usize = 10; let data = Arc::new((Mutex::new(0), Condvar::new())); let (tx, rx) = channel(); for _ in 0..N { let data = data.clone(); let tx = tx.clone(); thread::spawn(move|| { let &(ref lock, ref cond) = &*data; let mut cnt = lock.lock().unwrap(); *cnt += 1; if *cnt == N { tx.send(()).unwrap(); } while *cnt != 0 { cnt = cond.wait(cnt).unwrap(); } tx.send(()).unwrap(); }); } drop(tx); let &(ref lock, ref cond) = &*data; rx.recv().unwrap(); let mut cnt = lock.lock().unwrap(); *cnt = 0; cond.notify_all(); drop(cnt); for _ in 0..N { rx.recv().unwrap(); } } #[test] #[cfg_attr(target_os = "emscripten", ignore)] fn wait_until() { let pair = Arc::new((Mutex::new(false), Condvar::new())); let pair2 = pair.clone(); // Inside of our lock, spawn a new thread, and then wait for it to start. thread::spawn(move|| { let &(ref lock, ref cvar) = &*pair2; let mut started = lock.lock().unwrap(); *started = true; // We notify the condvar that the value has changed. cvar.notify_one(); }); // Wait for the thread to start up. let &(ref lock, ref cvar) = &*pair; let guard = cvar.wait_until(lock.lock().unwrap(), |started| { *started }); assert!(*guard.unwrap()); } #[test] #[cfg_attr(target_os = "emscripten", ignore)] #[cfg_attr(target_env = "sgx", ignore)] // FIXME: https://github.com/fortanix/rust-sgx/issues/31 fn wait_timeout_wait() { let m = Arc::new(Mutex::new(())); let c = Arc::new(Condvar::new()); loop { let g = m.lock().unwrap(); let (_g, no_timeout) = c.wait_timeout(g, Duration::from_millis(1)).unwrap(); // spurious wakeups mean this isn't necessarily true // so execute test again, if not timeout if !no_timeout.timed_out() { continue; } break; } } #[test] #[cfg_attr(target_os = "emscripten", ignore)] #[cfg_attr(target_env = "sgx", ignore)] // FIXME: https://github.com/fortanix/rust-sgx/issues/31 fn wait_timeout_until_wait() { let m = Arc::new(Mutex::new(())); let c = Arc::new(Condvar::new()); let g = m.lock().unwrap(); let (_g, wait) = c.wait_timeout_until(g, Duration::from_millis(1), |_| { false }).unwrap(); // no spurious wakeups. ensure it timed-out assert!(wait.timed_out()); } #[test] #[cfg_attr(target_os = "emscripten", ignore)] fn wait_timeout_until_instant_satisfy() { let m = Arc::new(Mutex::new(())); let c = Arc::new(Condvar::new()); let g = m.lock().unwrap(); let (_g, wait) = c.wait_timeout_until(g, Duration::from_millis(0), |_| { true }).unwrap(); // ensure it didn't time-out even if we were not given any time. assert!(!wait.timed_out()); } #[test] #[cfg_attr(target_os = "emscripten", ignore)] #[cfg_attr(target_env = "sgx", ignore)] // FIXME: https://github.com/fortanix/rust-sgx/issues/31 fn wait_timeout_until_wake() { let pair = Arc::new((Mutex::new(false), Condvar::new())); let pair_copy = pair.clone(); let &(ref m, ref c) = &*pair; let g = m.lock().unwrap(); let _t = thread::spawn(move || { let &(ref lock, ref cvar) = &*pair_copy; let mut started = lock.lock().unwrap(); thread::sleep(Duration::from_millis(1)); *started = true; cvar.notify_one(); }); let (g2, wait) = c.wait_timeout_until(g, Duration::from_millis(u64::MAX), |&mut notified| { notified }).unwrap(); // ensure it didn't time-out even if we were not given any time. assert!(!wait.timed_out()); assert!(*g2); } #[test] #[cfg_attr(target_os = "emscripten", ignore)] #[cfg_attr(target_env = "sgx", ignore)] // FIXME: https://github.com/fortanix/rust-sgx/issues/31 fn wait_timeout_wake() { let m = Arc::new(Mutex::new(())); let c = Arc::new(Condvar::new()); loop { let g = m.lock().unwrap(); let c2 = c.clone(); let m2 = m.clone(); let notified = Arc::new(AtomicBool::new(false)); let notified_copy = notified.clone(); let t = thread::spawn(move || { let _g = m2.lock().unwrap(); thread::sleep(Duration::from_millis(1)); notified_copy.store(true, Ordering::SeqCst); c2.notify_one(); }); let (g, timeout_res) = c.wait_timeout(g, Duration::from_millis(u64::MAX)).unwrap(); assert!(!timeout_res.timed_out()); // spurious wakeups mean this isn't necessarily true // so execute test again, if not notified if !notified.load(Ordering::SeqCst) { t.join().unwrap(); continue; } drop(g); t.join().unwrap(); break; } } #[test] #[should_panic] #[cfg_attr(target_os = "emscripten", ignore)] fn two_mutexes() { let m = Arc::new(Mutex::new(())); let m2 = m.clone(); let c = Arc::new(Condvar::new()); let c2 = c.clone(); let mut g = m.lock().unwrap(); let _t = thread::spawn(move|| { let _g = m2.lock().unwrap(); c2.notify_one(); }); g = c.wait(g).unwrap(); drop(g); let m = Mutex::new(()); let _ = c.wait(m.lock().unwrap()).unwrap(); } }