NAME
pthread_setschedprio —
dynamic thread scheduling parameters access (REALTIME
THREADS)
SYNOPSIS
int pthread_setschedprio(pthread_t thread, int prio);
DESCRIPTION
The pthread_setschedprio () function shall
set the scheduling priority for the thread whose thread ID is given by
thread
to the value given by
prio. See
V2_chap02(3) for a description on how this function call
affects the ordering of the thread in the thread list for its new
priority.
If the pthread_setschedprio () function
fails, the scheduling priority of the target thread shall not be
changed.
RETURN VALUE
If successful, the pthread_setschedprio ()
function shall return zero; otherwise, an error number shall be returned to
indicate the error.
ERRORS
The pthread_setschedprio () function may
fail if:
- [EINVAL]
- The value of prio is invalid for the scheduling policy of the specified thread.
- [ENOTSUP]
- An attempt was made to set the priority to an unsupported value.
- [EPERM]
- The caller does not have appropriate privileges to set the scheduling priority of the specified thread.
The pthread_setschedprio () function shall
not return an error code of [EINTR].
EXAMPLES
None.
APPLICATION USAGE
None.
RATIONALE
The pthread_setschedprio () function
provides a way for an application to temporarily raise its priority and then
lower it again, without having the undesired side-effect of yielding to
other threads of the same priority. This is necessary if the application is
to implement its own strategies for bounding priority inversion, such as
priority inheritance or priority ceilings. This capability is especially
important if the implementation does not support the Thread Priority
Protection or Thread Priority Inheritance options, but even if those options
are supported it is needed if the application is to bound priority
inheritance for other resources, such as semaphores.
The standard developers considered that while it might be preferable conceptually to solve this problem by modifying the specification of pthread_setschedparam(3), it was too late to make such a change, as there may be implementations that would need to be changed. Therefore, this new function was introduced.
If an implementation detects use of a thread ID after the end of its lifetime, it is recommended that the function should fail and report an [ESRCH] error.
FUTURE DIRECTIONS
None.
SEE ALSO
V2_chap02(3) , pthread_getschedparam(3)
XBD <pthread.h>
CHANGE HISTORY
First released in Issue 6. Included as a response to IEEE PASC Interpretation 1003.1 #96.
Issue 7
The pthread_setschedprio () function is
moved from the Threads option.
Austin Group Interpretation 1003.1-2001 #069 is applied, updating the [EPERM] error.
Austin Group Interpretation 1003.1-2001 #142 is applied, removing the [ESRCH] error condition.