pthread_attr_setschedparam()--Set Thread Attributes Object Scheduling Parameters

 #include <pthread.h>
 #include <sched.h>
 int pthread_attr_setschedparam(pthread_attr_t *attr, 
 		    const struct sched_param *param);

The pthread_attr_setschedparam() function sets the scheduling parameters in the thread attributes object. The supported i5/OS scheduling policy is SCHED_OTHER. Attempting to set the sched_policy field of the param parameter other than SCHED_OTHER causes the EINVAL error. The sched_priority field of the param parameter must range from PRIORITY_MIN to PRIORITY_MAX or the ENOTSUP error occurs.

All reserved fields in the scheduling parameters structure must be binary zero or the EINVAL error occurs.

Note: Do not use pthread_setschedparam() to set the priority of a thread if you also use another mechanism (outside of the pthread APIs) to set the priority of a thread. If you do, pthread_getschedparam() returns only that information that was set by the pthread interfaces (pthread_setschedparam() or modification of the thread attribute using pthread_attr_setschedparam()).

Authorities and Locks

None.

Parameters

attr

(Input/Output) The address of the thread attributes object

param

(Input) Address of the variable containing the scheduling parameters

Return Value

0

pthread_attr_setschedparam() was successful.

value

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

Error Conditions

If pthread_attr_setschedparam() was not successful, the error condition returned usually indicates one of the following errors. Under some conditions, the value returned could indicate an error other than those listed here.

[EINVAL]

The value specified for the argument is not correct.

[ENOTSUP]

The value specified for the priority argument is not supported.

Related Information

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

Example

See Code disclaimer information for information pertaining to code examples.

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

#define BUMP_PRIO 1
static int thePriority = 0;

void showSchedParam(pthread_attr_t *a)
{
  int                 rc=0;
  struct sched_param  param;

  printf("Get scheduling parameters\n");
  rc = pthread_attr_getschedparam(a, &param);
  checkResults("pthread_attr_getschedparam()\n", rc);

  printf("The thread attributes object indicates priority: %d\n",
         param.sched_priority);
  thePriority = param.sched_priority;
  return;
}

int main(int argc, char **argv)
{
  pthread_t             thread;
  int                   rc=0;
  pthread_attr_t        pta;
  struct sched_param    param;

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

  printf("Create a thread attributes object\n");
  rc = pthread_attr_init(&pta);
  checkResults("pthread_attr_init()\n", rc);

  showSchedParam(&pta);

  memset(&param, 0, sizeof(param));
  if (thePriority + BUMP_PRIO <= PRIORITY_MAX_NP) {
  param.sched_priority = thePriority + BUMP_PRIO;
  }

  printf("Setting scheduling parameters\n");
  rc = pthread_attr_setschedparam(&pta, &param);
  checkResults("pthread_attr_setschedparam()\n", rc);

  showSchedParam(&pta);

  printf("Destroy thread attributes object\n");
  rc = pthread_attr_destroy(&pta);
  checkResults("pthread_attr_destroy()\n", rc);

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

Output:

Enter Testcase - QP0WTEST/TASSP0
Create a thread attributes object
Get scheduling parameters
The thread attributes object indicates priority: 0
Setting scheduling parameters
Get scheduling parameters
The thread attributes object indicates priority: 0
Destroy thread attributes object
Main completed