pthread_cond_timedwait

Name

pthread_cond_timedwait
- wait on a condition variable for a specific amount of time

Library

libc_r.lib libpthread.lib libthr.lib

Synopsis

#include <pthread.h>

int pthread_cond_timedwait (pthread_cond_t *cond, pthread_mutex_t *mutex, const struct timespec *abstime);

Return values

If successful, the pthread_cond_timedwait function will return zero. Otherwise an error number will be returned to indicate the error.

Detailed description

The pthread_cond_timedwait function atomically blocks the current thread waiting on the condition variable specified by cond, and unblocks the mutex specified by mutex. The waiting thread unblocks only after another thread calls pthread_cond_signal, or pthread_cond_broadcast with the same condition variable, or if the system time reaches the time specified in abstime, and the current thread reacquires the lock on mutex.

Examples

struct testdata
{
 pthread_mutex_t mutex;
 pthread_cond_t  cond;
};
static struct testdata td;
 int rc;
 struct timespec timeout;
 struct timeval  curtime;
/* mutex and conditional variable must be initialized */
 if (pthread_mutex_lock(&td.mutex) != 0) {
  fprintf(stderr,"Thread: Fail to acquire mutex\n");
  return -1;
 }
 if (gettimeofday(&curtime, NULL) !=0 ) {
  fprintf(stderr,"Fail to get current time\n");
  return -1;
 }
 timeout.tv_sec = curtime.tv_sec;
 timeout.tv_nsec = curtime.tv_usec * 1000;
 timeout.tv_sec += TIMEOUT;
 fprintf(stderr,"Thread is waiting for the cond\n");
 rc = pthread_cond_timedwait(&td.cond, &td.mutex, &timeout);
 if(rc != 0) {
  if (rc == ETIMEDOUT) {
   fprintf(stderr,"Thread stops waiting when time is out\n");
   return -1;
  }
  else {
   fprintf(stderr,"pthread_cond_timedwait return %d\n", rc);
   return -1;
  }
 }
 fprintf(stderr,"Thread wakened up\n");
 pthread_mutex_unlock(&td.mutex);

Errors

The pthread_cond_timedwait function will fail if:

[`EINVAL`]
	The value specified by cond, mutex or abstime is invalid.
[`ETIMEDOUT`]
	The system time has reached or exceeded the time specified in abstime.
[`ENOMEM`]
	If this function was not able to acquire a required resource.

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