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Commit 311e800e authored by Hillf Danton's avatar Hillf Danton Committed by Ingo Molnar
Browse files

sched, rt: Fix rq->rt.pushable_tasks bug in push_rt_task() 



Do not call dequeue_pushable_task() when failing to push an eligible
task, as it remains pushable, merely not at this particular moment.

Signed-off-by: default avatarHillf Danton <dhillf@gmail.com>
Signed-off-by: default avatarMike Galbraith <mgalbraith@gmx.de>
Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Yong Zhang <yong.zhang0@gmail.com>
Link: http://lkml.kernel.org/r/1306895385.4791.26.camel@marge.simson.net


Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 08354716

kernel/sched_rt.c

+8 −7
Original line number Diff line number Diff line
@@ -1394,6 +1394,7 @@ static int push_rt_task(struct rq *rq) 
{

	struct task_struct *next_task;

	struct rq *lowest_rq;

	int ret = 0;



	if (!rq->rt.overloaded)

		return 0;
@@ -1426,7 +1427,7 @@ static int push_rt_task(struct rq *rq) 
	if (!lowest_rq) {

		struct task_struct *task;

		/*

		 * find lock_lowest_rq releases rq->lock

		 * find_lock_lowest_rq releases rq->lock

		 * so it is possible that next_task has migrated.

		 *

		 * We need to make sure that the task is still on the same
@@ -1436,12 +1437,11 @@ static int push_rt_task(struct rq *rq) 
		task = pick_next_pushable_task(rq);

		if (task_cpu(next_task) == rq->cpu && task == next_task) {

			/*

			 * If we get here, the task hasn't moved at all, but

			 * it has failed to push.  We will not try again,

			 * since the other cpus will pull from us when they

			 * are ready.

			 * The task hasn't migrated, and is still the next

			 * eligible task, but we failed to find a run-queue

			 * to push it to.  Do not retry in this case, since

			 * other cpus will pull from us when ready.

			 */

			dequeue_pushable_task(rq, next_task);

			goto out;

		}
@@ -1460,6 +1460,7 @@ static int push_rt_task(struct rq *rq) 
	deactivate_task(rq, next_task, 0);

	set_task_cpu(next_task, lowest_rq->cpu);

	activate_task(lowest_rq, next_task, 0);

	ret = 1;



	resched_task(lowest_rq->curr);
@@ -1468,7 +1469,7 @@ static int push_rt_task(struct rq *rq) 
out:

	put_task_struct(next_task);



	return 1;

	return ret;

}



static void push_rt_tasks(struct rq *rq)