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Diffstat (limited to 'ctr-std/src/sync/condvar.rs')
| -rw-r--r-- | ctr-std/src/sync/condvar.rs | 589 |
1 files changed, 589 insertions, 0 deletions
diff --git a/ctr-std/src/sync/condvar.rs b/ctr-std/src/sync/condvar.rs new file mode 100644 index 0000000..68c7e88 --- /dev/null +++ b/ctr-std/src/sync/condvar.rs @@ -0,0 +1,589 @@ +// Copyright 2014 The Rust Project Developers. See the COPYRIGHT +// file at the top-level directory of this distribution and at +// http://rust-lang.org/COPYRIGHT. +// +// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or +// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license +// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your +// option. This file may not be copied, modified, or distributed +// except according to those terms. + +use fmt; +use sync::atomic::{AtomicUsize, Ordering}; +use sync::{mutex, MutexGuard, PoisonError}; +use sys_common::condvar as sys; +use sys_common::mutex as sys_mutex; +use sys_common::poison::{self, LockResult}; +use time::Duration; + +/// 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 whether 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, 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 &(ref lock, ref cvar) = &*pair2; + /// let mut started = lock.lock().unwrap(); + /// // We update the boolean value. + /// *started = true; + /// // Let's wait 20 milliseconds before notifying the condvar. + /// thread::sleep(Duration::from_millis(20)); + /// cvar.notify_one(); + /// }); + /// + /// // Wait for the thread to start up. + /// let &(ref lock, ref 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 &(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 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 &(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 mut started = lock.lock().unwrap(); + /// // As long as the value inside the `Mutex` 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) + } + } + + /// 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 &(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 mut started = lock.lock().unwrap(); + /// // As long as the value inside the `Mutex` 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. + /// + /// 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 + /// [`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 &(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 mut started = lock.lock().unwrap(); + /// // as long as the value inside the `Mutex` 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)) + } + } + + /// 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 &(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 mut started = lock.lock().unwrap(); + /// // As long as the value inside the `Mutex` 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 &(ref lock, ref 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 &(ref lock, ref cvar) = &*pair; + /// let mut started = lock.lock().unwrap(); + /// // As long as the value inside the `Mutex` 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 = "1.9.0")] +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 sync::mpsc::channel; + use sync::{Condvar, Mutex, Arc}; + use thread; + use time::Duration; + use u32; + + #[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_timeout_ms() { + 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 (g, _no_timeout) = c.wait_timeout(g, Duration::from_millis(1)).unwrap(); + // spurious wakeups mean this isn't necessarily true + // assert!(!no_timeout); + let _t = thread::spawn(move || { + let _g = m2.lock().unwrap(); + c2.notify_one(); + }); + let (g, timeout_res) = c.wait_timeout(g, Duration::from_millis(u32::MAX as u64)).unwrap(); + assert!(!timeout_res.timed_out()); + drop(g); + } + + #[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(); + } +} |