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Commit 24600ce8 authored by Rusty Russell's avatar Rusty Russell Committed by Ingo Molnar
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sched: convert check_preempt_equal_prio to cpumask_var_t. 



Impact: stack reduction for large NR_CPUS

Dynamically allocating cpumasks (when CONFIG_CPUMASK_OFFSTACK) saves
stack space.

We simply return if the allocation fails: since we don't use it we
could just pass NULL to cpupri_find and have it handle that.

Signed-off-by: default avatarRusty Russell <rusty@rustcorp.com.au>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 68e74568

kernel/sched_rt.c

+10 −5
Original line number Diff line number Diff line
@@ -805,17 +805,20 @@ static int select_task_rq_rt(struct task_struct *p, int sync) 


static void check_preempt_equal_prio(struct rq *rq, struct task_struct *p)

{

	cpumask_t mask;

	cpumask_var_t mask;



	if (rq->curr->rt.nr_cpus_allowed == 1)

		return;



	if (p->rt.nr_cpus_allowed != 1

	    && cpupri_find(&rq->rd->cpupri, p, &mask))

	if (!alloc_cpumask_var(&mask, GFP_ATOMIC))

		return;



	if (!cpupri_find(&rq->rd->cpupri, rq->curr, &mask))

		return;

	if (p->rt.nr_cpus_allowed != 1

	    && cpupri_find(&rq->rd->cpupri, p, mask))

		goto free;



	if (!cpupri_find(&rq->rd->cpupri, rq->curr, mask))

		goto free;



	/*

	 * There appears to be other cpus that can accept
@@ -824,6 +827,8 @@ static void check_preempt_equal_prio(struct rq *rq, struct task_struct *p) 
	 */

	requeue_task_rt(rq, p, 1);

	resched_task(rq->curr);

free:

	free_cpumask_var(mask);

}



#endif /* CONFIG_SMP */