#include <sched.h>
int sched_yield(void);
Threadsafe: Yes
Signal Safe: Yes

The sched_yield() function yields the processor from the currently executing thread to another ready to run, active thread of equal or higher priority.

If there are currently no threads of equal or higher priority that are active and ready to run, sched_yield() will return immediately, and the calling thread will continue to run until its time slice has expired.

Parameters

None.

Authorities and Locks

None.

Return Value

0

sched_yield() was successful.

value

sched_yield() was not successful. value is set to indicate the error condition.

The sched_yield() API does not currently return an error.

Related Information

• The <pthread.h> header file. See Header files for Pthread functions
• pthread_getschedparam()--Get Thread Scheduling Parameters

#define _MULTI_THREADED
#include <pthread.h>
#include <stdio.h>
#include <errno.h>
#include "check.h"

#define            LOOPCONSTANT     1000
#define            THREADS          3

pthread_mutex_t    mutex = PTHREAD_MUTEX_INITIALIZER;
int                i,j,k,l;

void *threadfunc(void *parm)
{
  int   loop = 0;
  int   localProcessingCompleted = 0;
  int   numberOfLocalProcessingBursts = 0;
  int   processingCompletedThisBurst = 0;
  int   rc;

  printf("Entered secondary thread\n");
  for (loop=0; loop<LOOPCONSTANT; ++loop) {
    rc = pthread_mutex_lock(&mutex);
    checkResults("pthread_mutex_lock()\n", rc);
    /* Perform some not so important processing */
    i++, j++, k++, l++;

    rc = pthread_mutex_unlock(&mutex);
    checkResults("pthread_mutex_unlock()\n", rc);
    /* This work isn't too important. Also, we just released a lock
       and would like to ensure that other threads get a chance in
       a more co-operative manner. This is an admittedly contrived
       example with no real purpose for doing the sched_yield().
       */
    sched_yield();
  }
  printf("Finished secondary thread\n");
  return NULL;
}

int main(int argc, char **argv)
{
  pthread_t             threadid[THREADS];
  int                   rc=0;
  int                   loop=0;

  printf("Enter Testcase - %s\n", argv[0]);

  rc = pthread_mutex_lock(&mutex);
  checkResults("pthread_mutex_lock()\n", rc);

  printf("Creating %d threads\n", THREADS);
  for (loop=0; loop<THREADS; ++loop) {
    rc = pthread_create(&threadid[loop], NULL, threadfunc, NULL);
    checkResults("pthread_create()\n", rc);
  }

  sleep(1);
  rc = pthread_mutex_unlock(&mutex);
  checkResults("pthread_mutex_unlock()\n", rc);

  printf("Wait for results\n");
  for (loop=0; loop<THREADS; ++loop) {
    rc = pthread_join(threadid[loop], NULL);
    checkResults("pthread_join()\n", rc);
  }

  pthread_mutex_destroy(&mutex);

  printf("Main completed\n");
  return 0;
}

Enter Testcase - QP0WTEST/TPSCHY0
Creating 3 threads
Entered secondary thread
Entered secondary thread
Entered secondary thread
Wait for results
Finished secondary thread
Finished secondary thread
Finished secondary thread
Main completed