pthread_setschedparam()

QNX SDP8.0C Library ReferenceAPIDeveloper

Set thread scheduling parameters

Synopsis:

#include <pthread.h>

int pthread_setschedparam(
               pthread_t thread,
               int policy,
               const struct sched_param *param );

Arguments:

thread

The ID of the thread that you want to set the scheduling parameters for. You can get a thread ID by calling pthread_create() or pthread_self().

policy

The new scheduling policy; one of:

SCHED_FIFO — a fixed-priority scheduler in which the highest priority, ready thread runs until it blocks or is preempted by a higher priority thread.
SCHED_RR — the same as SCHED_FIFO, except threads at the same priority level timeslice (round robin) every 4 × the clock period (see ClockPeriod()).
SCHED_OTHER — currently the same as SCHED_RR.
SCHED_SPORADIC — sporadic scheduling. For more information, see pthread_attr_setschedpolicy(), and Scheduling policies in the chapter on the microkernel in the System Architecture guide.
SCHED_HIGH_PRIORITY_IST — a FIFO scheduling policy that allows a thread to go at or above the clock IST, but below 255.
Note:
The SCHED_HIGH_PRIORITY_IST policy is intended only for ISTs. For more information, see Interrupt Service Thread (IST) in the Programmer's Guide.
SCHED_OFFLINING — a FIFO scheduling policy intended for CPU offlining that allows a thread to be of higher priority than the clock IST.
Note:
- To set the SCHED_OFFLINING policy, the process must have the runstate ability enabled. For more information, go to Abilities in the QNX OS System Security Guide.
- The offlining and onlining scheduling feature is experimental.

For more information, see Thread scheduling in the IDE Microkernel chapter of the System Architecture guide.

param

A pointer to a sched_param structure that specifies the scheduling parameters that you want to use.

Library:

libc

Use the -l c option to qcc to link against this library. This library is usually included automatically.

Description:

The pthread_setschedparam() function sets the scheduling policy and associated scheduling parameters of thread thread to the values specified in policy and param.

Note:

In order to change the thread's priority to a value above the maximum permitted for unprivileged processes, your process must have the PROCMGR_AID_PRIORITY ability enabled. For more information, see procmgr_ability().

Returns:

EOK: Success.
EINVAL: Invalid scheduling policy policy or parameters param.
ENOTSUP: Unsupported scheduling policy policy or parameters param.
EPERM: The calling process doesn't have the required permission; see procmgr_ability().
ESRCH: Invalid thread ID thread.

Classification:

POSIX 1003.1 TPS


Safety:
Cancellation point	No
Signal handler	Yes
Thread	Yes

Page updated: August 11, 2025