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Commit d5f9f942 authored by Andrew Morton's avatar Andrew Morton Committed by Linus Torvalds
Browse files

revert 'sched: redundant reschedule when set_user_nice() boosts a prio of a... 


revert 'sched: redundant reschedule when set_user_nice() boosts a prio of a task from the "expired" array'

Revert commit bd53f96c.

Con says:

This is no good, sorry. The one I saw originally was with the staircase
deadline cpu scheduler in situ and was different.

  #define TASK_PREEMPTS_CURR(p, rq) \
     ((p)->prio < (rq)->curr->prio)
     (((p)->prio < (rq)->curr->prio) && ((p)->array == (rq)->active))

This will fail to wake up a runqueue for a task that has been migrated to the
expired array of a runqueue which is otherwise idle which can happen with smp
balancing,

Cc: Dmitry Adamushko <dmitry.adamushko@gmail.com>
Cc: Con Kolivas <kernel@kolivas.org>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent da4e8ca3

kernel/sched.c

+18 −16
Original line number Diff line number Diff line
@@ -169,7 +169,7 @@ unsigned long long __attribute__((weak)) sched_clock(void) 
		(MAX_BONUS / 2 + DELTA((p)) + 1) / MAX_BONUS - 1))



#define TASK_PREEMPTS_CURR(p, rq) \

	(((p)->prio < (rq)->curr->prio) && ((p)->array == (rq)->active))

	((p)->prio < (rq)->curr->prio)



#define SCALE_PRIO(x, prio) \

	max(x * (MAX_PRIO - prio) / (MAX_USER_PRIO / 2), MIN_TIMESLICE)
@@ -4076,13 +4076,13 @@ void rt_mutex_setprio(struct task_struct *p, int prio) 
	struct prio_array *array;

	unsigned long flags;

	struct rq *rq;

	int delta;

	int oldprio;



	BUG_ON(prio < 0 || prio > MAX_PRIO);



	rq = task_rq_lock(p, &flags);



	delta = prio - p->prio;

	oldprio = p->prio;

	array = p->array;

	if (array)

		dequeue_task(p, array);
@@ -4098,11 +4098,13 @@ void rt_mutex_setprio(struct task_struct *p, int prio) 
		enqueue_task(p, array);

		/*

		 * Reschedule if we are currently running on this runqueue and

		 * our priority decreased, or if our priority became higher

		 * than the current's.

		 * our priority decreased, or if we are not currently running on

		 * this runqueue and our priority is higher than the current's

		 */

		if (TASK_PREEMPTS_CURR(p, rq) ||

				(delta > 0 && task_running(rq, p)))

		if (task_running(rq, p)) {

			if (p->prio > oldprio)

				resched_task(rq->curr);

		} else if (TASK_PREEMPTS_CURR(p, rq))

			resched_task(rq->curr);

	}

	task_rq_unlock(rq, &flags);
@@ -4150,12 +4152,10 @@ void set_user_nice(struct task_struct *p, long nice) 
		enqueue_task(p, array);

		inc_raw_weighted_load(rq, p);

		/*

		 * Reschedule if we are currently running on this runqueue and

		 * our priority decreased, or if our priority became higher

		 * than the current's.

		 * If the task increased its priority or is running and

		 * lowered its priority, then reschedule its CPU:

		 */

		if (TASK_PREEMPTS_CURR(p, rq) ||

				(delta > 0 && task_running(rq, p)))

		if (delta < 0 || (delta > 0 && task_running(rq, p)))

			resched_task(rq->curr);

	}

out_unlock:
@@ -4382,11 +4382,13 @@ int sched_setscheduler(struct task_struct *p, int policy, 
		__activate_task(p, rq);

		/*

		 * Reschedule if we are currently running on this runqueue and

		 * our priority decreased, or our priority became higher

		 * than the current's.

		 * our priority decreased, or if we are not currently running on

		 * this runqueue and our priority is higher than the current's

		 */

		if (TASK_PREEMPTS_CURR(p, rq) ||

				(task_running(rq, p) && p->prio > oldprio))

		if (task_running(rq, p)) {

			if (p->prio > oldprio)

				resched_task(rq->curr);

		} else if (TASK_PREEMPTS_CURR(p, rq))

			resched_task(rq->curr);

	}

	__task_rq_unlock(rq);