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sched: Migrate throttled tasks on HOTPLUG

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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: Paul Turner <pjt@google.com>
Reviewed-by: Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/20110721184757.989000590@google.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Paul Turner 2011-07-21 09:43:38 -07:00 committed by Ingo Molnar
parent 5238cdd387
commit 8cb120d3e4
1 changed files with 27 additions and 0 deletions
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27
kernel/sched.c
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@ -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