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sched: Fix switch_from_fair()

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When a task is taken out of the fair class we must ensure the vruntime
is properly normalized because when we put it back in it will assume
to be normalized.

The case that goes wrong is when changing away from the fair class
while sleeping. Sleeping tasks have non-normalized vruntime in order
to make sleeper-fairness work. So treat the switch away from fair as a
wakeup and preserve the relative vruntime.

Also update sysrq-n to call the ->switch_{to,from} methods.

Reported-by: Onkalo Samu <samu.p.onkalo@nokia.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Peter Zijlstra
2011-01-17 17:03:27 +01:00
committed by Ingo Molnar
parent a8941d7ec8
commit da7a735e51
6 changed files with 69 additions and 39 deletions
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25
kernel/sched.c
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@@ -2057,14 +2057,14 @@ inline int task_curr(const struct task_struct *p)
static inline void check_class_changed(struct rq *rq, struct task_struct *p,
const struct sched_class *prev_class,
int oldprio, int running)
int oldprio)
{
if (prev_class != p->sched_class) {
if (prev_class->switched_from)
prev_class->switched_from(rq, p, running);
p->sched_class->switched_to(rq, p, running);
} else
p->sched_class->prio_changed(rq, p, oldprio, running);
prev_class->switched_from(rq, p);
p->sched_class->switched_to(rq, p);
} else if (oldprio != p->prio)
p->sched_class->prio_changed(rq, p, oldprio);
}
static void check_preempt_curr(struct rq *rq, struct task_struct *p, int flags)
@@ -2598,6 +2598,7 @@ static void __sched_fork(struct task_struct *p)
p->se.sum_exec_runtime = 0;
p->se.prev_sum_exec_runtime = 0;
p->se.nr_migrations = 0;
p->se.vruntime = 0;
#ifdef CONFIG_SCHEDSTATS
memset(&p->se.statistics, 0, sizeof(p->se.statistics));
@@ -4696,11 +4697,10 @@ void rt_mutex_setprio(struct task_struct *p, int prio)
if (running)
p->sched_class->set_curr_task(rq);
if (on_rq) {
if (on_rq)
enqueue_task(rq, p, oldprio < prio ? ENQUEUE_HEAD : 0);
check_class_changed(rq, p, prev_class, oldprio, running);
}
check_class_changed(rq, p, prev_class, oldprio);
task_rq_unlock(rq, &flags);
}
@@ -5028,11 +5028,10 @@ recheck:
if (running)
p->sched_class->set_curr_task(rq);
if (on_rq) {
if (on_rq)
activate_task(rq, p, 0);
check_class_changed(rq, p, prev_class, oldprio, running);
}
check_class_changed(rq, p, prev_class, oldprio);
__task_rq_unlock(rq);
raw_spin_unlock_irqrestore(&p->pi_lock, flags);
@@ -8237,6 +8236,8 @@ EXPORT_SYMBOL(__might_sleep);
#ifdef CONFIG_MAGIC_SYSRQ
static void normalize_task(struct rq *rq, struct task_struct *p)
{
const struct sched_class *prev_class = p->sched_class;
int old_prio = p->prio;
int on_rq;
on_rq = p->se.on_rq;
@@ -8247,6 +8248,8 @@ static void normalize_task(struct rq *rq, struct task_struct *p)
activate_task(rq, p, 0);
resched_task(rq->curr);
}
check_class_changed(rq, p, prev_class, old_prio);
}
void normalize_rt_tasks(void)