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mark 2020-06-11 21:31:49 -05:00
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library/std/src/sync/condvar.rs Normal file
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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 provided condition is false.
///
/// 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
///
/// ```
/// use std::sync::{Arc, Mutex, Condvar};
/// use std::thread;
///
/// let pair = Arc::new((Mutex::new(true), Condvar::new()));
/// let pair2 = pair.clone();
///
/// thread::spawn(move|| {
/// let (lock, cvar) = &*pair2;
/// let mut pending = lock.lock().unwrap();
/// *pending = false;
/// // 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 `true`, we wait.
/// let _guard = cvar.wait_while(lock.lock().unwrap(), |pending| { *pending }).unwrap();
/// ```
#[stable(feature = "wait_until", since = "1.42.0")]
pub fn wait_while<'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 timeout 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_while` method
/// to wait with a timeout while a predicate is true.
///
/// 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_while`]: #method.wait_timeout_while
/// [`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.
///
/// The semantics of this function are equivalent to [`wait_while`] 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_while`], the lock specified will be re-acquired when this
/// function returns, regardless of whether the timeout elapsed or not.
///
/// [`wait_while`]: #method.wait_while
/// [`wait_timeout`]: #method.wait_timeout
/// [`WaitTimeoutResult`]: struct.WaitTimeoutResult.html
///
/// # Examples
///
/// ```
/// use std::sync::{Arc, Mutex, Condvar};
/// use std::thread;
/// use std::time::Duration;
///
/// let pair = Arc::new((Mutex::new(true), Condvar::new()));
/// let pair2 = pair.clone();
///
/// thread::spawn(move|| {
/// let (lock, cvar) = &*pair2;
/// let mut pending = lock.lock().unwrap();
/// *pending = false;
/// // 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_while(
/// lock.lock().unwrap(),
/// Duration::from_millis(100),
/// |&mut pending| pending,
/// ).unwrap();
/// if result.1.timed_out() {
/// // timed-out without the condition ever evaluating to false.
/// }
/// // access the locked mutex via result.0
/// ```
#[stable(feature = "wait_timeout_until", since = "1.42.0")]
pub fn wait_timeout_while<'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 {
use crate::sync::atomic::{AtomicBool, Ordering};
use crate::sync::mpsc::channel;
use crate::sync::{Arc, Condvar, Mutex};
use crate::thread;
use crate::time::Duration;
#[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_while() {
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_while(lock.lock().unwrap(), |started| !*started);
assert!(*guard.unwrap());
}
#[test]
#[cfg_attr(target_os = "emscripten", ignore)]
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)]
fn wait_timeout_while_wait() {
let m = Arc::new(Mutex::new(()));
let c = Arc::new(Condvar::new());
let g = m.lock().unwrap();
let (_g, wait) = c.wait_timeout_while(g, Duration::from_millis(1), |_| true).unwrap();
// no spurious wakeups. ensure it timed-out
assert!(wait.timed_out());
}
#[test]
#[cfg_attr(target_os = "emscripten", ignore)]
fn wait_timeout_while_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_while(g, Duration::from_millis(0), |_| false).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)]
fn wait_timeout_while_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_while(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)]
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();
}
}