Messages in this thread Patch in this message | | | From | Greg Kroah-Hartman <> | Subject | [PATCH 4.4 050/103] sched/fair: Do not announce throttled next buddy in dequeue_task_fair() | Date | Tue, 23 May 2017 22:09:16 +0200 |
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4.4-stable review patch. If anyone has any objections, please let me know.
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From: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
commit 754bd598be9bbc953bc709a9e8ed7f3188bfb9d7 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>
--- kernel/sched/fair.c | 9 ++++----- 1 file changed, 4 insertions(+), 5 deletions(-)
--- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -4233,15 +4233,14 @@ static void dequeue_task_fair(struct rq /* Don't dequeue parent if it has other entities besides us */ 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 * p is sleeping when it is within its sched_slice. */ - if (task_sleep && parent_entity(se)) - set_next_buddy(parent_entity(se)); - - /* avoid re-evaluating load for this entity */ - se = parent_entity(se); + if (task_sleep && se && !throttled_hierarchy(cfs_rq)) + set_next_buddy(se); break; } flags |= DEQUEUE_SLEEP;
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