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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: Mike Galbraith <efault@gmx.de>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1311779695.8691.2.camel@marge.simson.net
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Mike Galbraith 2011-07-27 17:14:55 +02:00 committed by Ingo Molnar
parent 2c2efaed9b
commit c350a04efd
1 changed files with 12 additions and 13 deletions
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25
kernel/sched.c
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@ -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;
set_load_weight(p);
}
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;