Struct ConditionVariable 

pub struct ConditionVariable {
    waiters: SpinLock<VecDeque<ParkHandle>>,
}

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.

Fields

waiters: SpinLock<VecDeque<ParkHandle>>

Implementations

impl ConditionVariable

pub fn new() -> Self

Creates a new condition variable which is ready to be waited on and signaled.

pub fn wait_while<'a, T>( &self, mutex: &'a Mutex<T>, predicate: impl Fn(&mut T) -> bool, ) -> MutexGuard<'a, T>

Blocks the current thread while predicate returns true.

This function takes reference of a Mutex and checks the predicate. If it returns true, the thread is blocked and the mutex is temporarily released. When the thread is signaled and wakes up, it reacquires the mutex and re-evaluates the predicate. This loop continues until the predicate returns false.

Example

let guard = condvar.wait_while(&mutex, |state| state.count == 0);

There is no need to check the predicate before calling wait_while. It performs the entire check-and-sleep logic internally.

pub fn signal<'a, T>(&self, guard: MutexGuard<'a, T>)

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_while. Calls to signal are not buffered in any way.

To wake up all threads, see broadcast.

pub fn broadcast<'a, T>(&self, guard: MutexGuard<'a, T>)

Wakes up all blocked threads on this condvar.

This method will ensure that any current waiters on the condition variable are awoken. Calls to broadcast() are not buffered in any way.

To wake up only one thread, see signal.

Trait Implementations

impl Default for ConditionVariable

fn default() -> ConditionVariable

Returns the “default value” for a type.