Commit d49db342 authored Jun 24, 2015 by Cong Wang Committed by Ingo Molnar Jul 06, 2015

sched/fair: Test list head instead of list entry in throttle_cfs_rq()



According to the comments, we need to test if this is
the first throttled task, however, list_empty() tests on
the entry cfs_rq->throttled_list, not the head, this is wrong.

This is a bug because we don't re-init the list entry after
removing it from the list, so list_empty() could return false
even if the list is really empty.

Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: Cong Wang <cwang@twopensource.com>
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/1435174907-432-1-git-send-email-xiyou.wangcong@gmail.com


Signed-off-by: Ingo Molnar <mingo@kernel.org>

parent 1c4c7159

kernel/sched/fair.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -3683,7 +3683,7 @@ static void throttle_cfs_rq(struct cfs_rq *cfs_rq)
		cfs_rq->throttled = 1;
		cfs_rq->throttled_clock = rq_clock(rq);
		raw_spin_lock(&cfs_b->lock);
		empty = list_empty(&cfs_rq->throttled_list);
		empty = list_empty(&cfs_b->throttled_cfs_rq);

		/*
		* Add to the _head_ of the list, so that an already-started

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