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Commit c350a04e authored by Mike Galbraith's avatar Mike Galbraith Committed by Ingo Molnar
Browse files

sched: fix broken SCHED_RESET_ON_FORK handling 



Setting child->prio = current->normal_prio _after_ SCHED_RESET_ON_FORK has
been handled for an RT parent gives birth to a deranged mutant child with
non-RT policy, but RT prio and sched_class.

Move PI leakage protection up, always set priorities and weight, and if the
child is leaving RT class, reset rt_priority to the proper value.

Signed-off-by: default avatarMike Galbraith <efault@gmx.de>
Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1311779695.8691.2.camel@marge.simson.net


Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 2c2efaed

kernel/sched.c

+12 −13
Original line number Diff line number Diff line
@@ -2843,20 +2843,24 @@ void sched_fork(struct task_struct *p) 
	 */

	p->state = TASK_RUNNING;



	/*

	 * Make sure we do not leak PI boosting priority to the child.

	 */

	p->prio = current->normal_prio;



	/*

	 * Revert to default priority/policy on fork if requested.

	 */

	if (unlikely(p->sched_reset_on_fork)) {

		if (p->policy == SCHED_FIFO || p->policy == SCHED_RR) {

		if (task_has_rt_policy(p)) {

			p->policy = SCHED_NORMAL;

			p->normal_prio = p->static_prio;

		}



		if (PRIO_TO_NICE(p->static_prio) < 0) {

			p->static_prio = NICE_TO_PRIO(0);

			p->normal_prio = p->static_prio;

			p->rt_priority = 0;

		} else if (PRIO_TO_NICE(p->static_prio) < 0)

			p->static_prio = NICE_TO_PRIO(0);



		p->prio = p->normal_prio = __normal_prio(p);

		set_load_weight(p);

		}



		/*

		 * We don't need the reset flag anymore after the fork. It has
@@ -2865,11 +2869,6 @@ void sched_fork(struct task_struct *p) 
		p->sched_reset_on_fork = 0;

	}



	/*

	 * Make sure we do not leak PI boosting priority to the child.

	 */

	p->prio = current->normal_prio;



	if (!rt_prio(p->prio))

		p->sched_class = &fair_sched_class;