AIX Version 4.3 Base Operating System and Extensions Technical Reference, Volume

pthread_setschedparam Subroutine


Returns the current schedpolicy and schedparam attributes of a thread.


Threads Library (libpthreads.a)




int pthread_setschedparam (thread, schedpolicy, schedparam)

pthread_t thread;

int schedpolicy;

const struct sched_param *schedparam;


The pthread_setschedparam subroutine dynamically sets the schedpolicy and
schedparam attributes of the thread thread. The schedpolicy attibute specifies
the scheduling policy of the thread. The schedparam attribute specifies the
scheduling parameters of a thread created with this attributes object. The
sched_priority field of the sched_param structure contains the priority of the
thread. It is an integer value.

If the target thread has system contention scope, the process must have root
authority to set the scheduling policy to either SCHED_FIFO or SCHED_RR.

    Note: The pthread.h header file must be the first included file of each
    source file using the threads library. Otherwise, the -D_THREAD_SAFE
    compilation flag should be used, or the cc_r compiler used. In this case, the
    flag is automatically set.


thread Specifies the target thread.

schedpolicy Points to the schedpolicy attribute to set. It must have one of the
following values:

SCHED_FIFO Denotes first-in first-out scheduling.

SCHED_RR Denotes round-robin scheduling.

SCHED_OTHER Denotes the default AIX scheduling policy. It is the default value.

    Note: It is not permitted to change the priority of a thread when setting its
    scheduling policy to SCHED_OTHER. In this case, the priority is managed
    directly by the kernel, and the only legal value that can be passed to
    pthread_setschedparam is DEFAULT_PRIO, which is defined in pthread.h as 1.

schedparam Points to where the scheduling parameters to set are stored. The
sched_priority field must be in the range from 1 to 127, where 1 is the least
favored priority, and 127 the most favored.

Return Values

Upon successful completion, 0 is returned. Otherwise, an error code is returned.

Error Codes

The pthread_setschedparam subroutine is unsuccessful if the following is true:

EINVAL The thread or schedparam parameters are not valid.

ENOSYS The priority scheduling POSIX option is not implemented.

ENOTSUP The value of the schedpolicy or schedparam attributes are not supported.

EPERM The target thread has insufficient permission to perform the operation or
is already engaged in a mutex protocol.

ESRCH The thread thread does not exist.

Implementation Specifics

This subroutine is part of the Base Operating System (BOS) Runtime. The
implementation of this subroutine is dependent on the priority scheduling POSIX
option. The priority scheduling POSIX option is implemented in AIX.

Related Information

The pthread_getschedparam subroutine, pthread_attr_setschedpolicy subroutine,
pthread_attr_setschedparam subroutine.

Threads Scheduling in AIX Version 4.3 General Programming Concepts: Writing and
Debugging Programs.

Threads Library Options in AIX Version 4.3 General Programming Concepts: Writing
and Debugging Programs.

Threads Library Quick Reference in AIX Version 4.3 General Programming Concepts:
Writing and Debugging Programs.