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Commit 8cb120d3 authored by Paul Turner's avatar Paul Turner Committed by Ingo Molnar
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sched: Migrate throttled tasks on HOTPLUG 



Throttled tasks are invisisble to cpu-offline since they are not eligible for
selection by pick_next_task().  The regular 'escape' path for a thread that is
blocked at offline is via ttwu->select_task_rq, however this will not handle a
throttled group since there are no individual thread wakeups on an unthrottle.

Resolve this by unthrottling offline cpus so that threads can be migrated.

Signed-off-by: default avatarPaul Turner <pjt@google.com>
Reviewed-by: default avatarHidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>
Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/20110721184757.989000590@google.com


Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 5238cdd3

kernel/sched.c

+27 −0
Original line number Diff line number Diff line
@@ -6335,6 +6335,30 @@ static void calc_global_load_remove(struct rq *rq) 
	rq->calc_load_active = 0;

}



#ifdef CONFIG_CFS_BANDWIDTH

static void unthrottle_offline_cfs_rqs(struct rq *rq)

{

	struct cfs_rq *cfs_rq;



	for_each_leaf_cfs_rq(rq, cfs_rq) {

		struct cfs_bandwidth *cfs_b = tg_cfs_bandwidth(cfs_rq->tg);



		if (!cfs_rq->runtime_enabled)

			continue;



		/*

		 * clock_task is not advancing so we just need to make sure

		 * there's some valid quota amount

		 */

		cfs_rq->runtime_remaining = cfs_b->quota;

		if (cfs_rq_throttled(cfs_rq))

			unthrottle_cfs_rq(cfs_rq);

	}

}

#else

static void unthrottle_offline_cfs_rqs(struct rq *rq) {}

#endif



/*

 * Migrate all tasks from the rq, sleeping tasks will be migrated by

 * try_to_wake_up()->select_task_rq().
@@ -6360,6 +6384,9 @@ static void migrate_tasks(unsigned int dead_cpu) 
	 */

	rq->stop = NULL;



	/* Ensure any throttled groups are reachable by pick_next_task */

	unthrottle_offline_cfs_rqs(rq);



	for ( ; ; ) {

		/*

		 * There's this thread running, bail when that's the only