PR_WaitCondVar

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 value PR_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 with PR_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.