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sched/fair: Do not announce throttled next buddy in dequeue_task_fair()

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commit 754bd598be upstream.

Hierarchy could be already throttled at this point. Throttled next
buddy could trigger a NULL pointer dereference in pick_next_task_fair().

Signed-off-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Ben Segall <bsegall@google.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/146608183552.21905.15924473394414832071.stgit@buzz
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: Ben Pineau <benjamin.pineau@mirakl.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Konstantin Khlebnikov
2016-06-16 15:57:15 +03:00
committed by Greg Kroah-Hartman
parent ae3d7b8931
commit f01ae9cb0d
1 changed files with 4 additions and 5 deletions
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9
kernel/sched/fair.c
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@@ -4233,15 +4233,14 @@ static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
/* Don't dequeue parent if it has other entities besides us */ /* Don't dequeue parent if it has other entities besides us */
if (cfs_rq->load.weight) { if (cfs_rq->load.weight) {
/* Avoid re-evaluating load for this entity: */
se = parent_entity(se);
/* /*
* Bias pick_next to pick a task from this cfs_rq, as * Bias pick_next to pick a task from this cfs_rq, as
* p is sleeping when it is within its sched_slice. * p is sleeping when it is within its sched_slice.
*/ */
if (task_sleep && parent_entity(se)) if (task_sleep && se && !throttled_hierarchy(cfs_rq))
set_next_buddy(parent_entity(se)); set_next_buddy(se);
/* avoid re-evaluating load for this entity */
se = parent_entity(se);
break; break;
} }
flags |= DEQUEUE_SLEEP; flags |= DEQUEUE_SLEEP;