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Message-Id: <1418745509-2609-1-git-send-email-pang.xunlei@linaro.org> Date: Tue, 16 Dec 2014 23:58:29 +0800 From: Xunlei Pang <pang.xunlei@...aro.org> To: linux-kernel@...r.kernel.org Cc: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>, Xunlei Pang <pang.xunlei@...aro.org> Subject: [PATCH] sched/fair: Fix the dealing with decay_count in __synchronize_entity_decay() In __synchronize_entity_decay(), if "decays" happens to be zero, se->avg.decay_count will not be zeroed, holding the positive value assigned when dequeued last time. This is problematic in the following case: If this runnable task is CFS-balanced to other CPUs soon afterwards, migrate_task_rq_fair() will treat it as a blocked task due to its non-zero decay_count, thereby adding its load to cfs_rq->removed_load wrongly. Thus, we must zero se->avg.decay_count in this case as well. Signed-off-by: Xunlei Pang <pang.xunlei@...aro.org> --- kernel/sched/fair.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index df2cdf7..ea517cd 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -2574,11 +2574,11 @@ static inline u64 __synchronize_entity_decay(struct sched_entity *se) u64 decays = atomic64_read(&cfs_rq->decay_counter); decays -= se->avg.decay_count; + se->avg.decay_count = 0; if (!decays) return 0; se->avg.load_avg_contrib = decay_load(se->avg.load_avg_contrib, decays); - se->avg.decay_count = 0; return decays; } -- 1.9.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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