Waits on a condition.
Syntax
#include <prcvar.h> PRStatus PR_WaitCondVar( PRCondVar *cvar, PRIntervalTime timeout);
Parameters
PR_WaitCondVar
has the following parameters:
cvar
- The condition variable on which to wait.
timeout
- The value
PR_INTERVAL_NO_TIMEOUT
requires that a condition be notified (or the thread interrupted) before it will resume from the wait. The valuePR_INTERVAL_NO_WAIT
causes the thread to release the lock, possibly causing a rescheduling within the runtime, then immediately attempt to reacquire the lock and resume.
Returns
The function returns one of the following values:
- If successful,
PR_SUCCESS
. - If unsuccessful (for example, if the caller has not locked the lock associated with the condition variable or the thread was interrupted with
PR_Interrupt
),PR_FAILURE
. The details can be determined withPR_GetError
.
Description
Before the call to PR_WaitCondVar
, the lock associated with the condition variable must be held by the calling thread. After a call to PR_WaitCondVar
, the lock is released and the thread is blocked in a "waiting on condition" state until another thread notifies the condition or a caller-specified amount of time expires.
When the condition variable is notified, a thread waiting on that condition moves from the "waiting on condition" state to the "ready" state. When scheduled, the thread attempts to reacquire the lock that it held when PR_WaitCondVar
was called.
Any value other than PR_INTERVAL_NO_TIMEOUT
or PR_INTERVAL_NO_WAIT
for the timeout parameter will cause the thread to be rescheduled due to either explicit notification or the expiration of the specified interval. The latter must be determined by treating time as one part of the monitored data being protected by the lock and tested explicitly for an expired interval. To detect the expiration of the specified interval, call PR_IntervalNow
before and after the call to PR_WaitCondVar
and compare the elapsed time with the specified interval.