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// Copyright 2016 Amanieu d'Antras
//
// Licensed under the Apache License, Version 2.0, <LICENSE-APACHE or
// copied, modified, or distributed except according to those terms.
use crate::mutex::MutexGuard;
use crate::raw_mutex::{RawMutex, TOKEN_HANDOFF, TOKEN_NORMAL};
use crate::{deadlock, util};
use core::{
fmt, ptr,
sync::atomic::{AtomicPtr, Ordering},
};
use lock_api::RawMutex as RawMutex_;
use parking_lot_core::{self, ParkResult, RequeueOp, UnparkResult, DEFAULT_PARK_TOKEN};
use std::ops::DerefMut;
use std::time::{Duration, Instant};
/// A type indicating whether a timed wait on a condition variable returned
/// due to a time out or not.
#[derive(Debug, PartialEq, Eq, Copy, Clone)]
pub struct WaitTimeoutResult(bool);
impl WaitTimeoutResult {
/// Returns whether the wait was known to have timed out.
#[inline]
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 thread must block.
///
/// Note that this module places one additional restriction over the system
/// condition variables: each condvar can be used with only one mutex at a
/// time. Any attempt to use multiple mutexes on the same condition variable
/// simultaneously will result in a runtime panic. However it is possible to
/// switch to a different mutex if there are no threads currently waiting on
/// the condition variable.
///
/// # Differences from the standard library `Condvar`
///
/// - No spurious wakeups: A wait will only return a non-timeout result if it
/// was woken up by `notify_one` or `notify_all`.
/// - `Condvar::notify_all` will only wake up a single thread, the rest are
/// requeued to wait for the `Mutex` to be unlocked by the thread that was
/// woken up.
/// - Only requires 1 word of space, whereas the standard library boxes the
/// `Condvar` due to platform limitations.
/// - Can be statically constructed.
/// - Does not require any drop glue when dropped.
/// - Inline fast path for the uncontended case.
///
/// # Examples
///
/// ```
/// use parking_lot::{Mutex, Condvar};
/// use std::sync::Arc;
/// 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 &(ref lock, ref cvar) = &*pair2;
/// let mut started = lock.lock();
/// *started = true;
/// cvar.notify_one();
/// });
///
/// // wait for the thread to start up
/// let &(ref lock, ref cvar) = &*pair;
/// let mut started = lock.lock();
/// if !*started {
/// cvar.wait(&mut started);
/// }
/// // Note that we used an if instead of a while loop above. This is only
/// // possible because parking_lot's Condvar will never spuriously wake up.
/// // This means that wait() will only return after notify_one or notify_all is
/// // called.
/// ```
pub struct Condvar {
state: AtomicPtr<RawMutex>,
}
impl Condvar {
/// Creates a new condition variable which is ready to be waited on and
/// notified.
#[inline]
pub const fn new() -> Condvar {
Condvar {
state: AtomicPtr::new(ptr::null_mut()),
}
}
/// Wakes up one blocked thread on this condvar.
///
/// Returns whether a thread was woken up.
///
/// 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()`.
///
/// # Examples
///
/// ```
/// use parking_lot::Condvar;
///
/// let condvar = Condvar::new();
///
/// // do something with condvar, share it with other threads
///
/// if !condvar.notify_one() {
/// println!("Nobody was listening for this.");
/// }
/// ```
#[inline]
pub fn notify_one(&self) -> bool {
// Nothing to do if there are no waiting threads
let state = self.state.load(Ordering::Relaxed);
if state.is_null() {
return false;
}
self.notify_one_slow(state)
}
#[cold]
fn notify_one_slow(&self, mutex: *mut RawMutex) -> bool {
// Unpark one thread and requeue the rest onto the mutex
let from = self as *const _ as usize;
let to = mutex as usize;
let validate = || {
// Make sure that our atomic state still points to the same
// mutex. If not then it means that all threads on the current
// mutex were woken up and a new waiting thread switched to a
// different mutex. In that case we can get away with doing
// nothing.
if self.state.load(Ordering::Relaxed) != mutex {
return RequeueOp::Abort;
}
// Unpark one thread if the mutex is unlocked, otherwise just
// requeue everything to the mutex. This is safe to do here
// since unlocking the mutex when the parked bit is set requires
// locking the queue. There is the possibility of a race if the
// mutex gets locked after we check, but that doesn't matter in
// this case.
if unsafe { (*mutex).mark_parked_if_locked() } {
RequeueOp::RequeueOne
} else {
RequeueOp::UnparkOne
}
};
let callback = |_op, result: UnparkResult| {
// Clear our state if there are no more waiting threads
if !result.have_more_threads {
self.state.store(ptr::null_mut(), Ordering::Relaxed);
}
TOKEN_NORMAL
};
let res = unsafe { parking_lot_core::unpark_requeue(from, to, validate, callback) };
res.unparked_threads + res.requeued_threads != 0
}
/// Wakes up all blocked threads on this condvar.
///
/// Returns the number of threads woken up.
///
/// 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()`.
#[inline]
pub fn notify_all(&self) -> usize {
// Nothing to do if there are no waiting threads
let state = self.state.load(Ordering::Relaxed);
if state.is_null() {
return 0;
}
self.notify_all_slow(state)
}
#[cold]
fn notify_all_slow(&self, mutex: *mut RawMutex) -> usize {
// Unpark one thread and requeue the rest onto the mutex
let from = self as *const _ as usize;
let to = mutex as usize;
let validate = || {
// Make sure that our atomic state still points to the same
// mutex. If not then it means that all threads on the current
// mutex were woken up and a new waiting thread switched to a
// different mutex. In that case we can get away with doing
// nothing.
if self.state.load(Ordering::Relaxed) != mutex {
return RequeueOp::Abort;
}
// Clear our state since we are going to unpark or requeue all
// threads.
self.state.store(ptr::null_mut(), Ordering::Relaxed);
// Unpark one thread if the mutex is unlocked, otherwise just
// requeue everything to the mutex. This is safe to do here
// since unlocking the mutex when the parked bit is set requires
// locking the queue. There is the possibility of a race if the
// mutex gets locked after we check, but that doesn't matter in
// this case.
if unsafe { (*mutex).mark_parked_if_locked() } {
RequeueOp::RequeueAll
} else {
RequeueOp::UnparkOneRequeueRest
}
};
let callback = |op, result: UnparkResult| {
// If we requeued threads to the mutex, mark it as having
// parked threads. The RequeueAll case is already handled above.
if op == RequeueOp::UnparkOneRequeueRest && result.requeued_threads != 0 {
unsafe { (*mutex).mark_parked() };
}
TOKEN_NORMAL
};
let res = unsafe { parking_lot_core::unpark_requeue(from, to, validate, callback) };
res.unparked_threads + res.requeued_threads
}
/// Blocks the current thread until this condition variable receives a
/// notification.
///
/// This function will atomically unlock the mutex specified (represented by
/// `mutex_guard`) and block the current thread. This means that any calls
/// to `notify_*()` 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.
///
/// # Panics
///
/// This function will panic if another thread is waiting on the `Condvar`
/// with a different `Mutex` object.
#[inline]
pub fn wait<T: ?Sized>(&self, mutex_guard: &mut MutexGuard<'_, T>) {
self.wait_until_internal(unsafe { MutexGuard::mutex(mutex_guard).raw() }, None);
}
/// Waits on this condition variable for a notification, timing out after
/// the specified time instant.
///
/// The semantics of this function are equivalent to `wait()` except that
/// the thread will be blocked roughly until `timeout` is reached. 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 `timeout`.
///
/// 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.
///
/// Like `wait`, the lock specified will be re-acquired when this function
/// returns, regardless of whether the timeout elapsed or not.
///
/// # Panics
///
/// This function will panic if another thread is waiting on the `Condvar`
/// with a different `Mutex` object.
#[inline]
pub fn wait_until<T: ?Sized>(
&self,
mutex_guard: &mut MutexGuard<'_, T>,
timeout: Instant,
) -> WaitTimeoutResult {
self.wait_until_internal(
unsafe { MutexGuard::mutex(mutex_guard).raw() },
Some(timeout),
)
}
// This is a non-generic function to reduce the monomorphization cost of
// using `wait_until`.
fn wait_until_internal(&self, mutex: &RawMutex, timeout: Option<Instant>) -> WaitTimeoutResult {
let result;
let mut bad_mutex = false;
let mut requeued = false;
{
let addr = self as *const _ as usize;
let lock_addr = mutex as *const _ as *mut _;
let validate = || {
// Ensure we don't use two different mutexes with the same
// Condvar at the same time. This is done while locked to
// avoid races with notify_one
let state = self.state.load(Ordering::Relaxed);
if state.is_null() {
self.state.store(lock_addr, Ordering::Relaxed);
} else if state != lock_addr {
bad_mutex = true;
return false;
}
true
};
let before_sleep = || {
// Unlock the mutex before sleeping...
unsafe { mutex.unlock() };
};
let timed_out = |k, was_last_thread| {
// If we were requeued to a mutex, then we did not time out.
// We'll just park ourselves on the mutex again when we try
// to lock it later.
requeued = k != addr;
// If we were the last thread on the queue then we need to
// clear our state. This is normally done by the
// notify_{one,all} functions when not timing out.
if !requeued && was_last_thread {
self.state.store(ptr::null_mut(), Ordering::Relaxed);
}
};
result = unsafe { parking_lot_core::park(
addr,
validate,
before_sleep,
timed_out,
DEFAULT_PARK_TOKEN,
timeout,
) };
}
// Panic if we tried to use multiple mutexes with a Condvar. Note
// that at this point the MutexGuard is still locked. It will be
// unlocked by the unwinding logic.
if bad_mutex {
panic!("attempted to use a condition variable with more than one mutex");
}
// ... and re-lock it once we are done sleeping
if result == ParkResult::Unparked(TOKEN_HANDOFF) {
unsafe { deadlock::acquire_resource(mutex as *const _ as usize) };
} else {
mutex.lock();
}
WaitTimeoutResult(!(result.is_unparked() || requeued))
}
/// 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 `timeout`. 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 `timeout`.
///
/// 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.
///
/// Like `wait`, the lock specified will be re-acquired when this function
/// returns, regardless of whether the timeout elapsed or not.
#[inline]
pub fn wait_for<T: ?Sized>(
&self,
mutex_guard: &mut MutexGuard<'_, T>,
timeout: Duration,
) -> WaitTimeoutResult {
let deadline = util::to_deadline(timeout);
self.wait_until_internal(unsafe { MutexGuard::mutex(mutex_guard).raw() }, deadline)
}
#[inline]
fn wait_while_until_internal<T, F>(
&self,
mutex_guard: &mut MutexGuard<'_, T>,
mut condition: F,
timeout: Option<Instant>,
) -> WaitTimeoutResult
where
T: ?Sized,
F: FnMut(&mut T) -> bool,
{
let mut result = WaitTimeoutResult(false);
while !result.timed_out() && condition(mutex_guard.deref_mut()) {
result =
self.wait_until_internal(unsafe { MutexGuard::mutex(mutex_guard).raw() }, timeout);
}
result
}
/// Blocks the current thread until this condition variable receives a
/// notification. If the provided condition evaluates to `false`, then the
/// thread is no longer blocked and the operation is completed. If the
/// condition evaluates to `true`, then the thread is blocked again and
/// waits for another notification before repeating this process.
///
/// This function will atomically unlock the mutex specified (represented by
/// `mutex_guard`) and block the current thread. This means that any calls
/// to `notify_*()` 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.
///
/// # Panics
///
/// This function will panic if another thread is waiting on the `Condvar`
/// with a different `Mutex` object.
#[inline]
pub fn wait_while<T, F>(&self, mutex_guard: &mut MutexGuard<'_, T>, condition: F)
where
T: ?Sized,
F: FnMut(&mut T) -> bool,
{
self.wait_while_until_internal(mutex_guard, condition, None);
}
/// Waits on this condition variable for a notification, timing out after
/// the specified time instant. If the provided condition evaluates to
/// `false`, then the thread is no longer blocked and the operation is
/// completed. If the condition evaluates to `true`, then the thread is
/// blocked again and waits for another notification before repeating
/// this process.
///
/// The semantics of this function are equivalent to `wait()` except that
/// the thread will be blocked roughly until `timeout` is reached. 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 `timeout`.
///
/// 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.
///
/// Like `wait`, the lock specified will be re-acquired when this function
/// returns, regardless of whether the timeout elapsed or not.
///
/// # Panics
///
/// This function will panic if another thread is waiting on the `Condvar`
/// with a different `Mutex` object.
#[inline]
pub fn wait_while_until<T, F>(
&self,
mutex_guard: &mut MutexGuard<'_, T>,
condition: F,
timeout: Instant,
) -> WaitTimeoutResult
where
T: ?Sized,
F: FnMut(&mut T) -> bool,
{
self.wait_while_until_internal(mutex_guard, condition, Some(timeout))
}
/// Waits on this condition variable for a notification, timing out after a
/// specified duration. If the provided condition evaluates to `false`,
/// then the thread is no longer blocked and the operation is completed.
/// If the condition evaluates to `true`, then the thread is blocked again
/// and waits for another notification before repeating this process.
///
/// The semantics of this function are equivalent to `wait()` except that
/// the thread will be blocked for roughly no longer than `timeout`. 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 `timeout`.
///
/// 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.
///
/// Like `wait`, the lock specified will be re-acquired when this function
/// returns, regardless of whether the timeout elapsed or not.
#[inline]
pub fn wait_while_for<T: ?Sized, F>(
&self,
mutex_guard: &mut MutexGuard<'_, T>,
condition: F,
timeout: Duration,
) -> WaitTimeoutResult
where
F: FnMut(&mut T) -> bool,
{
let deadline = util::to_deadline(timeout);
self.wait_while_until_internal(mutex_guard, condition, deadline)
}
}
impl Default for Condvar {
#[inline]
fn default() -> Condvar {
Condvar::new()
}
}
impl fmt::Debug for Condvar {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.pad("Condvar { .. }")
}
}
#[cfg(test)]
mod tests {
use crate::{Condvar, Mutex, MutexGuard};
use std::sync::mpsc::channel;
use std::sync::Arc;
use std::thread;
use std::thread::sleep;
use std::thread::JoinHandle;
use std::time::Duration;
use std::time::Instant;
#[test]
fn smoke() {
let c = Condvar::new();
c.notify_one();
c.notify_all();
}
#[test]
fn notify_one() {
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();
let _t = thread::spawn(move || {
let _g = m2.lock();
c2.notify_one();
});
c.wait(&mut g);
}
#[test]
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();
*cnt += 1;
if *cnt == N {
tx.send(()).unwrap();
}
while *cnt != 0 {
cond.wait(&mut cnt);
}
tx.send(()).unwrap();
});
}
drop(tx);
let &(ref lock, ref cond) = &*data;
rx.recv().unwrap();
let mut cnt = lock.lock();
*cnt = 0;
cond.notify_all();
drop(cnt);
for _ in 0..N {
rx.recv().unwrap();
}
}
#[test]
fn notify_one_return_true() {
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();
let _t = thread::spawn(move || {
let _g = m2.lock();
assert!(c2.notify_one());
});
c.wait(&mut g);
}
#[test]
fn notify_one_return_false() {
let m = Arc::new(Mutex::new(()));
let c = Arc::new(Condvar::new());
let _t = thread::spawn(move || {
let _g = m.lock();
assert!(!c.notify_one());
});
}
#[test]
fn notify_all_return() {
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();
*cnt += 1;
if *cnt == N {
tx.send(()).unwrap();
}
while *cnt != 0 {
cond.wait(&mut cnt);
}
tx.send(()).unwrap();
});
}
drop(tx);
let &(ref lock, ref cond) = &*data;
rx.recv().unwrap();
let mut cnt = lock.lock();
*cnt = 0;
assert_eq!(cond.notify_all(), N);
drop(cnt);
for _ in 0..N {
rx.recv().unwrap();
}
assert_eq!(cond.notify_all(), 0);
}
#[test]
fn wait_for() {
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();
let no_timeout = c.wait_for(&mut g, Duration::from_millis(1));
assert!(no_timeout.timed_out());
let _t = thread::spawn(move || {
let _g = m2.lock();
c2.notify_one();
});
let timeout_res = c.wait_for(&mut g, Duration::from_secs(u64::max_value()));
assert!(!timeout_res.timed_out());
drop(g);
}
#[test]
fn wait_until() {
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();
let no_timeout = c.wait_until(&mut g, Instant::now() + Duration::from_millis(1));
assert!(no_timeout.timed_out());
let _t = thread::spawn(move || {
let _g = m2.lock();
c2.notify_one();
});
let timeout_res = c.wait_until(
&mut g,
Instant::now() + Duration::from_millis(u32::max_value() as u64),
);
assert!(!timeout_res.timed_out());
drop(g);
}
fn spawn_wait_while_notifier(
mutex: Arc<Mutex<u32>>,
cv: Arc<Condvar>,
num_iters: u32,
timeout: Option<Instant>,
) -> JoinHandle<()> {
thread::spawn(move || {
for epoch in 1..=num_iters {
// spin to wait for main test thread to block
// before notifying it to wake back up and check
// its condition.
let mut sleep_backoff = Duration::from_millis(1);
let _mutex_guard = loop {
let mutex_guard = mutex.lock();
if let Some(timeout) = timeout {
if Instant::now() >= timeout {
return;
}
}
if *mutex_guard == epoch {
break mutex_guard;
}
drop(mutex_guard);
// give main test thread a good chance to
// acquire the lock before this thread does.
sleep(sleep_backoff);
sleep_backoff *= 2;
};
cv.notify_one();
}
})
}
#[test]
fn wait_while_until_internal_does_not_wait_if_initially_false() {
let mutex = Arc::new(Mutex::new(0));
let cv = Arc::new(Condvar::new());
let condition = |counter: &mut u32| {
*counter += 1;
false
};
let mut mutex_guard = mutex.lock();
let timeout_result = cv
.wait_while_until_internal(&mut mutex_guard, condition, None);
assert!(!timeout_result.timed_out());
assert!(*mutex_guard == 1);
}
#[test]
fn wait_while_until_internal_times_out_before_false() {
let mutex = Arc::new(Mutex::new(0));
let cv = Arc::new(Condvar::new());
let num_iters = 3;
let condition = |counter: &mut u32| {
*counter += 1;
true
};
let mut mutex_guard = mutex.lock();
let timeout = Some(Instant::now() + Duration::from_millis(500));
let handle = spawn_wait_while_notifier(mutex.clone(), cv.clone(), num_iters, timeout);
let timeout_result =
cv.wait_while_until_internal(&mut mutex_guard, condition, timeout);
assert!(timeout_result.timed_out());
assert!(*mutex_guard == num_iters + 1);
// prevent deadlock with notifier
drop(mutex_guard);
handle.join().unwrap();
}
#[test]
fn wait_while_until_internal() {
let mutex = Arc::new(Mutex::new(0));
let cv = Arc::new(Condvar::new());
let num_iters = 4;
let condition = |counter: &mut u32| {
*counter += 1;
*counter <= num_iters
};
let mut mutex_guard = mutex.lock();
let handle = spawn_wait_while_notifier(mutex.clone(), cv.clone(), num_iters, None);
let timeout_result =
cv.wait_while_until_internal(&mut mutex_guard, condition, None);
assert!(!timeout_result.timed_out());
assert!(*mutex_guard == num_iters + 1);
let timeout_result = cv.wait_while_until_internal(&mut mutex_guard, condition, None);
handle.join().unwrap();
assert!(!timeout_result.timed_out());
assert!(*mutex_guard == num_iters + 2);
}
#[test]
#[should_panic]
fn two_mutexes() {
let m = Arc::new(Mutex::new(()));
let m2 = m.clone();
let m3 = Arc::new(Mutex::new(()));
let c = Arc::new(Condvar::new());
let c2 = c.clone();
// Make sure we don't leave the child thread dangling
struct PanicGuard<'a>(&'a Condvar);
impl<'a> Drop for PanicGuard<'a> {
fn drop(&mut self) {
self.0.notify_one();
}
}
let (tx, rx) = channel();
let g = m.lock();
let _t = thread::spawn(move || {
let mut g = m2.lock();
tx.send(()).unwrap();
c2.wait(&mut g);
});
drop(g);
rx.recv().unwrap();
let _g = m.lock();
let _guard = PanicGuard(&*c);
c.wait(&mut m3.lock());
}
#[test]
fn two_mutexes_disjoint() {
let m = Arc::new(Mutex::new(()));
let m2 = m.clone();
let m3 = Arc::new(Mutex::new(()));
let c = Arc::new(Condvar::new());
let c2 = c.clone();
let mut g = m.lock();
let _t = thread::spawn(move || {
let _g = m2.lock();
c2.notify_one();
});
c.wait(&mut g);
drop(g);
let _ = c.wait_for(&mut m3.lock(), Duration::from_millis(1));
}
#[test]
fn test_debug_condvar() {
let c = Condvar::new();
assert_eq!(format!("{:?}", c), "Condvar { .. }");
}
#[test]
fn test_condvar_requeue() {
let m = Arc::new(Mutex::new(()));
let m2 = m.clone();
let c = Arc::new(Condvar::new());
let c2 = c.clone();
let t = thread::spawn(move || {
let mut g = m2.lock();
c2.wait(&mut g);
});
let mut g = m.lock();
while !c.notify_one() {
// Wait for the thread to get into wait()
MutexGuard::bump(&mut g);
// Yield, so the other thread gets a chance to do something.
// (At least Miri needs this, because it doesn't preempt threads.)
thread::yield_now();
}
// The thread should have been requeued to the mutex, which we wake up now.
drop(g);
t.join().unwrap();
}
#[test]
fn test_issue_129() {
let locks = Arc::new((Mutex::new(()), Condvar::new()));
let (tx, rx) = channel();
for _ in 0..4 {
let locks = locks.clone();
let tx = tx.clone();
thread::spawn(move || {
let mut guard = locks.0.lock();
locks.1.wait(&mut guard);
locks.1.wait_for(&mut guard, Duration::from_millis(1));
locks.1.notify_one();
tx.send(()).unwrap();
});
}
thread::sleep(Duration::from_millis(100));
locks.1.notify_one();
for _ in 0..4 {
assert_eq!(rx.recv_timeout(Duration::from_millis(500)), Ok(()));
}
}
}
/// This module contains an integration test that is heavily inspired from WebKit's own integration
/// tests for it's own Condvar.
#[cfg(test)]
mod webkit_queue_test {
use crate::{Condvar, Mutex, MutexGuard};
use std::{collections::VecDeque, sync::Arc, thread, time::Duration};
#[derive(Clone, Copy)]
enum Timeout {
Bounded(Duration),
Forever,
}
#[derive(Clone, Copy)]
enum NotifyStyle {
One,
All,
}
struct Queue {
items: VecDeque<usize>,
should_continue: bool,
}
impl Queue {
fn new() -> Self {
Self {
items: VecDeque::new(),
should_continue: true,
}
}
}
fn wait<T: ?Sized>(
condition: &Condvar,
lock: &mut MutexGuard<'_, T>,
predicate: impl Fn(&mut MutexGuard<'_, T>) -> bool,
timeout: &Timeout,
) {
while !predicate(lock) {
match timeout {
Timeout::Forever => condition.wait(lock),
Timeout::Bounded(bound) => {
condition.wait_for(lock, *bound);
}
}
}
}
fn notify(style: NotifyStyle, condition: &Condvar, should_notify: bool) {
match style {
NotifyStyle::One => {
condition.notify_one();
}
NotifyStyle::All => {
if should_notify {
condition.notify_all();
}
}
}
}
fn run_queue_test(
num_producers: usize,
num_consumers: usize,
max_queue_size: usize,
messages_per_producer: usize,
notify_style: NotifyStyle,
timeout: Timeout,
delay: Duration,
) {
let input_queue = Arc::new(Mutex::new(Queue::new()));
let empty_condition = Arc::new(Condvar::new());
let full_condition = Arc::new(Condvar::new());
let output_vec = Arc::new(Mutex::new(vec![]));
let consumers = (0..num_consumers)
.map(|_| {
consumer_thread(
input_queue.clone(),
empty_condition.clone(),
full_condition.clone(),
timeout,
notify_style,
output_vec.clone(),
max_queue_size,
)
})
.collect::<Vec<_>>();
let producers = (0..num_producers)
.map(|_| {
producer_thread(
messages_per_producer,
input_queue.clone(),
empty_condition.clone(),
full_condition.clone(),
timeout,
notify_style,
max_queue_size,
)
})
.collect::<Vec<_>>();
thread::sleep(delay);
for producer in producers.into_iter() {
producer.join().expect("Producer thread panicked");
}
{
let mut input_queue = input_queue.lock();
input_queue.should_continue = false;
}
empty_condition.notify_all();
for consumer in consumers.into_iter() {
consumer.join().expect("Consumer thread panicked");
}
let mut output_vec = output_vec.lock();
assert_eq!(output_vec.len(), num_producers * messages_per_producer);
output_vec.sort();
for msg_idx in 0..messages_per_producer {
for producer_idx in 0..num_producers {
assert_eq!(msg_idx, output_vec[msg_idx * num_producers + producer_idx]);
}
}
}
fn consumer_thread(
input_queue: Arc<Mutex<Queue>>,
empty_condition: Arc<Condvar>,
full_condition: Arc<Condvar>,
timeout: Timeout,
notify_style: NotifyStyle,
output_queue: Arc<Mutex<Vec<usize>>>,
max_queue_size: usize,
) -> thread::JoinHandle<()> {
thread::spawn(move || loop {
let (should_notify, result) = {
let mut queue = input_queue.lock();
wait(
&*empty_condition,
&mut queue,
|state| -> bool { !state.items.is_empty() || !state.should_continue },
&timeout,
);
if queue.items.is_empty() && !queue.should_continue {
return;
}
let should_notify = queue.items.len() == max_queue_size;
let result = queue.items.pop_front();
std::mem::drop(queue);
(should_notify, result)
};
notify(notify_style, &*full_condition, should_notify);
if let Some(result) = result {
output_queue.lock().push(result);
}
})
}
fn producer_thread(
num_messages: usize,
queue: Arc<Mutex<Queue>>,
empty_condition: Arc<Condvar>,
full_condition: Arc<Condvar>,
timeout: Timeout,
notify_style: NotifyStyle,
max_queue_size: usize,
) -> thread::JoinHandle<()> {
thread::spawn(move || {
for message in 0..num_messages {
let should_notify = {
let mut queue = queue.lock();
wait(
&*full_condition,
&mut queue,
|state| state.items.len() < max_queue_size,
&timeout,
);
let should_notify = queue.items.is_empty();
queue.items.push_back(message);
std::mem::drop(queue);
should_notify
};
notify(notify_style, &*empty_condition, should_notify);
}
})
}
macro_rules! run_queue_tests {
( $( $name:ident(
num_producers: $num_producers:expr,
num_consumers: $num_consumers:expr,
max_queue_size: $max_queue_size:expr,
messages_per_producer: $messages_per_producer:expr,
notification_style: $notification_style:expr,
timeout: $timeout:expr,
delay_seconds: $delay_seconds:expr);
)* ) => {
$(#[test]
fn $name() {
let delay = Duration::from_secs($delay_seconds);
run_queue_test(
$num_producers,
$num_consumers,
$max_queue_size,
$messages_per_producer,
$notification_style,
$timeout,
delay,
);
})*
};
}
run_queue_tests! {
sanity_check_queue(
num_producers: 1,
num_consumers: 1,
max_queue_size: 1,
messages_per_producer: 100_000,
notification_style: NotifyStyle::All,
timeout: Timeout::Bounded(Duration::from_secs(1)),
delay_seconds: 0
);
sanity_check_queue_timeout(
num_producers: 1,
num_consumers: 1,
max_queue_size: 1,
messages_per_producer: 100_000,
notification_style: NotifyStyle::All,
timeout: Timeout::Forever,
delay_seconds: 0
);
new_test_without_timeout_5(
num_producers: 1,
num_consumers: 5,
max_queue_size: 1,
messages_per_producer: 100_000,
notification_style: NotifyStyle::All,
timeout: Timeout::Forever,
delay_seconds: 0
);
one_producer_one_consumer_one_slot(
num_producers: 1,
num_consumers: 1,
max_queue_size: 1,
messages_per_producer: 100_000,
notification_style: NotifyStyle::All,
timeout: Timeout::Forever,
delay_seconds: 0
);
one_producer_one_consumer_one_slot_timeout(
num_producers: 1,
num_consumers: 1,
max_queue_size: 1,
messages_per_producer: 100_000,
notification_style: NotifyStyle::All,
timeout: Timeout::Forever,
delay_seconds: 1
);
one_producer_one_consumer_hundred_slots(
num_producers: 1,
num_consumers: 1,
max_queue_size: 100,
messages_per_producer: 1_000_000,
notification_style: NotifyStyle::All,
timeout: Timeout::Forever,
delay_seconds: 0
);
ten_producers_one_consumer_one_slot(
num_producers: 10,
num_consumers: 1,
max_queue_size: 1,
messages_per_producer: 10000,
notification_style: NotifyStyle::All,
timeout: Timeout::Forever,
delay_seconds: 0
);
ten_producers_one_consumer_hundred_slots_notify_all(
num_producers: 10,
num_consumers: 1,
max_queue_size: 100,
messages_per_producer: 10000,
notification_style: NotifyStyle::All,
timeout: Timeout::Forever,
delay_seconds: 0
);
ten_producers_one_consumer_hundred_slots_notify_one(
num_producers: 10,
num_consumers: 1,
max_queue_size: 100,
messages_per_producer: 10000,
notification_style: NotifyStyle::One,
timeout: Timeout::Forever,
delay_seconds: 0
);
one_producer_ten_consumers_one_slot(
num_producers: 1,
num_consumers: 10,
max_queue_size: 1,
messages_per_producer: 10000,
notification_style: NotifyStyle::All,
timeout: Timeout::Forever,
delay_seconds: 0
);
one_producer_ten_consumers_hundred_slots_notify_all(
num_producers: 1,
num_consumers: 10,
max_queue_size: 100,
messages_per_producer: 100_000,
notification_style: NotifyStyle::All,
timeout: Timeout::Forever,
delay_seconds: 0
);
one_producer_ten_consumers_hundred_slots_notify_one(
num_producers: 1,
num_consumers: 10,
max_queue_size: 100,
messages_per_producer: 100_000,
notification_style: NotifyStyle::One,
timeout: Timeout::Forever,
delay_seconds: 0
);
ten_producers_ten_consumers_one_slot(
num_producers: 10,
num_consumers: 10,
max_queue_size: 1,
messages_per_producer: 50000,
notification_style: NotifyStyle::All,
timeout: Timeout::Forever,
delay_seconds: 0
);
ten_producers_ten_consumers_hundred_slots_notify_all(
num_producers: 10,
num_consumers: 10,
max_queue_size: 100,
messages_per_producer: 50000,
notification_style: NotifyStyle::All,
timeout: Timeout::Forever,
delay_seconds: 0
);
ten_producers_ten_consumers_hundred_slots_notify_one(
num_producers: 10,
num_consumers: 10,
max_queue_size: 100,
messages_per_producer: 50000,
notification_style: NotifyStyle::One,
timeout: Timeout::Forever,
delay_seconds: 0
);
}
}