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Commit 7855a35a authored by Byungchul Park's avatar Byungchul Park Committed by Ingo Molnar
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sched: Ensure a task has a non-normalized vruntime when returning back to CFS 



Current code ensures that a task has a normalized vruntime when switching away
from the fair class, but it does not ensure the task has a non-normalized
vruntime when switching back to the fair class.

This is an example breaking this consistency:

  1. a task is in fair class and !queued
  2. changes its class to RT class (still !queued)
  3. changes its class to fair class again (still !queued)

Signed-off-by: default avatarByungchul Park <byungchul.park@lge.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1439197375-27927-1-git-send-email-byungchul.park@lge.com


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent e237882b

kernel/sched/fair.c

+17 −2
Original line number Diff line number Diff line
@@ -7930,16 +7930,31 @@ static void switched_from_fair(struct rq *rq, struct task_struct *p) 
 */

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

{

#ifdef CONFIG_FAIR_GROUP_SCHED

	struct sched_entity *se = &p->se;



#ifdef CONFIG_FAIR_GROUP_SCHED

	/*

	 * Since the real-depth could have been changed (only FAIR

	 * class maintain depth value), reset depth properly.

	 */

	se->depth = se->parent ? se->parent->depth + 1 : 0;

#endif

	if (!task_on_rq_queued(p))



	if (!task_on_rq_queued(p)) {



		/*

		 * Ensure the task has a non-normalized vruntime when it is switched

		 * back to the fair class with !queued, so that enqueue_entity() at

		 * wake-up time will do the right thing.

		 *

		 * If it's queued, then the enqueue_entity(.flags=0) makes the task

		 * has non-normalized vruntime, if it's !queued, then it still has

		 * normalized vruntime.

		 */

		if (p->state != TASK_RUNNING)

			se->vruntime += cfs_rq_of(se)->min_vruntime;

		return;

	}



	/*

	 * We were most likely switched from sched_rt, so