SCHED_SETPRIO is used for pthread_setschedprio() - for some reason this is not doc'd

http://www.opengroup.org/onlinepubs/009695399/functions/pthread_setschedprio.html

The rationale says it all...

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(), 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.

Sönke Nielsen wrote:
> In ker/nano_sched.c sched_thread() 
> 
> Why does a thread goes to the head of the priority queue in case of a lower priority?
> 
> if (new_prio != thp->priority) {
> 	int	lowered = (new_prio < thp->priority);
> 
> 		adjust_priority(thp, new_prio, thp->dpp, 0);
> 
> 	// If we lowered priority, ensure we will be head of priority list
> 	if (lowered && thp->state == STATE_READY) {
> 		LINK3_REM(DISPATCH_LST(thp->dpp, thp->priority), thp, THREAD);
> 		LINK3_BEG(DISPATCH_LST(thp->dpp, thp->priority), thp, THREAD);
> 	}
> }
> 
> Thanks
> Sönke
> 
> 
> 
> _______________________________________________
> 
> OSTech
> http://community.qnx.com/sf/go/post36495

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