pthread_setschedparam()--Set Target Thread Scheduling Parameters
Syntax:
#include <pthread.h> #include <sched.h> int pthread_setschedparam(pthread_t thread, int policy, const struct sched_param *param);Service Program Name: QP0WPTHR
Default Public Authority: *USE
Threadsafe: Yes
Signal Safe: No
The pthread_setschedparam() function sets the scheduling parameters of the target thread. The supported IBM® i scheduling policy is SCHED_OTHER. An attempt to set the policy to a value other than this cause 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 0 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
- thread
- (Input) Pthread handle of the target thread
- policy
- (Input) Scheduling policy (must be SCHED_OTHER)
- param
- (Input) Scheduling parameters
Return Value
- 0
- pthread_setschedparam() was successful.
- value
- pthread_setschedparam() was not successful. value is set to indicate the error condition.
Error Conditions
If pthread_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.
- pthread_getschedparam()--Get Thread Scheduling Parameters
Example
Note: By using the code examples, you agree to the terms of the Code license and disclaimer information.
#define _MULTI_THREADED #include <pthread.h> #include <sched.h> #include <stdio.h> #include "check.h" #define BUMP_PRIO 1 int thePriority = 0; int showSchedParam(pthread_t thread) { struct sched_param param; int policy; int rc; printf("Get scheduling parameters\n"); rc = pthread_getschedparam(thread, &policy, ¶m); checkResults("pthread_getschedparam()\n", rc); printf("The thread scheduling parameters indicate:\n" "priority = %d\n", param.sched_priority); return param.sched_priority; } void *threadfunc(void *parm) { int rc; printf("Inside secondary thread\n"); thePriority = showSchedParam(pthread_self()); sleep(5); /* Sleep is not a very robust way to serialize threads */ return NULL; } int main(int argc, char **argv) { pthread_t thread; int rc=0; struct sched_param param; int policy = SCHED_OTHER; int theChangedPriority=0; printf("Enter Testcase - %s\n", argv[0]); printf("Create thread using default attributes\n"); rc = pthread_create(&thread, NULL, threadfunc, NULL); checkResults("pthread_create()\n", rc); sleep(2); /* Sleep is not a very robust way to serialize threads */ memset(¶m, 0, sizeof(param)); /* Bump the priority of the thread a small amount */ if (thePriority - BUMP_PRIO >= PRIORITY_MIN_NP) { param.sched_priority = thePriority - BUMP_PRIO; } printf("Set scheduling parameters, prio=%d\n", param.sched_priority); rc = pthread_setschedparam(thread, policy, ¶m); checkResults("pthread_setschedparam()\n", rc); /* Let the thread fill in its own last priority */ theChangedPriority = showSchedParam(thread); if (thePriority == theChangedPriority || param.sched_priority != theChangedPriority) { printf("The thread did not get priority set correctly, " "first=%d last=%d expected=%d\n", thePriority, theChangedPriority, param.sched_priority); exit(1); } sleep(5); /* Sleep is not a very robust way to serialize threads */ printf("Main completed\n"); return 0; }
Output:
Enter Testcase - QP0WTEST/TPSSP0 Create thread using default attributes Inside secondary thread Get scheduling parameters The thread scheduling parameters indicate: priority = 0 Set scheduling parameters, prio=-1 Get scheduling parameters The thread scheduling parameters indicate: priority = -1 Main completed
API introduced: V4R3
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