pthread_cond

Name

pthread_cond_signal
- unblock a thread waiting for a condition variable

Library

libc_r.lib libpthread.lib libthr.lib

Synopsis

#include <pthread.h>

int pthread_cond_signal (pthread_cond_t *cond);

Return values

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

Detailed description

The pthread_cond_signal function unblocks one thread waiting for the condition variable cond.

Examples

 int rc;
struct testdata
{
 pthread_mutex_t mutex;
 pthread_cond_t  cond;
};
static struct testdata td;
int function1()
{
 if (pthread_mutex_init(&td.mutex, NULL) != 0) {
  fprintf(stderr,"Fail to initialize mutex\n");
  return -1;
 }
 if (pthread_cond_init(&td.cond, NULL) != 0) {
  fprintf(stderr,"Fail to initialize cond\n");
  return -1;
 }
 /* ....... other thread wait for signal */
 /* Acquire the mutex to make sure that all waiters are currently 
    blocked on pthread_cond_wait */
 if (pthread_mutex_lock(&td.mutex) != 0) {
  fprintf(stderr,"Main: Fail to acquire mutex\n");
  return -1;
 }
 if (pthread_mutex_unlock(&td.mutex) != 0) {
  fprintf(stderr,"Main: Fail to release mutex\n");
  return -1;
 }
 /* signal the condition to wake up all waiters */
 fprintf(stderr," signal the condition\n");
 rc = pthread_cond_signal(&td.cond);
 if (rc != 0) {
  fprintf(stderr," failed to signal the condition\n");
  return -1;
 }
}

Errors

The pthread_cond_signal function will fail if:

[`EINVAL`]
	The value specified by cond is invalid.

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