pthread_cond

Name

pthread_cond_wait
- wait on a condition variable

Library

libc_r.lib libpthread.lib libthr.lib

Synopsis

#include <pthread.h>

int pthread_cond_wait (pthread_cond_t *cond, pthread_mutex_t *mutex);

Return values

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

Detailed description

The pthread_cond_wait 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, 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;
/* mutex and conditional variable must be initialized */
if (pthread_mutex_lock(&td.mutex) != 0) {
  fprintf(stderr,"Thread failed to acquire mutex\n");
  return -1;
 }
fprintf(stderr,"Thread started\n");
fprintf(stderr,"Thread is waiting for the cond\n");
rc = pthread_cond_wait(&td.cond, &td.mutex);
if (rc != 0) {
  fprintf(stderr,"pthread_cond_wait return %d\n", rc);
  return -1;
}
fprintf(stderr,"Thread wakened\n");
pthread_mutex_unlock(&td.mutex);

Errors

The pthread_cond_wait function will fail if:

[`EINVAL`]
	The value specified by cond or the value specified by mutex is invalid.
[`ENOMEM`]
	This function was not able to acquire a required resource.
[`ETIMEDOUT`]
	The absolute time specified by abstime parameter occurred before the condition variable was signaled.

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