Struct pinned_sync::Condvar

pub struct Condvar { /* fields omitted */ }

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. Note that any attempt to use multiple mutexes on the same condition variable may result in a runtime panic.

Implementations

impl Condvar

pub const fn uninit() -> Self

Create a new, uninitialized condvar.

This is NOT equivalent to MaybeUninit::uninit().assume_init(), which will cause undefined behaviour if used to create a new condvar.

pub fn init(self: Pin<&Self>)

Initialize a condvar, making it ready for use.

Panics

This function may panic if the condvar was already initialized.

pub fn boxed() -> Pin<Box<Self>>

Create a new, initialized condition variable.

The resulting condition variable is wrapped and ready for use.

pub fn arc() -> Pin<Arc<Self>>

Create a new, initialized condition variable.

The resulting condition variable is wrapped and ready for use.

pub fn notify_one(self: Pin<&Self>)

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.

Panics

This function may panic if the condvar is not initialized.

pub fn notify_all(self: Pin<&Self>)

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.

Panics

This function may panic if the condvar is not initialized.

pub fn wait<'a, T>(
    self: Pin<&Self>,
    lock: MutexGuard<'a, T>
) -> LockResult<MutexGuard<'a, T>>

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 may panic! if it is used with more than one mutex over time.

This function may panic if the condvar is not initialized.

pub fn wait_while<'a, T, F>(
    self: Pin<&Self>,
    guard: MutexGuard<'a, T>,
    condition: F
) -> LockResult<MutexGuard<'a, T>> where
    F: FnMut(&mut T) -> bool, 

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.

Panics

This function may panic! if it is used with more than one mutex over time.

This function may panic if the condvar is not initialized.

pub fn wait_timeout<'a, T>(
    self: Pin<&Self>,
    lock: MutexGuard<'a, T>,
    dur: Duration
) -> LockResult<(MutexGuard<'a, T>, WaitTimeoutResult)>

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.

Panics

This function may panic! if it is used with more than one mutex over time.

This function may panic if the condvar is not initialized.

pub fn wait_timeout_while<'a, T, F>(
    self: Pin<&Self>,
    guard: MutexGuard<'a, T>,
    dur: Duration,
    condition: F
) -> LockResult<(MutexGuard<'a, T>, WaitTimeoutResult)> where
    F: FnMut(&mut T) -> bool, 

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.

Panics

This function may panic! if it is used with more than one mutex over time.

This function may panic if the condvar is not initialized.