Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751647AbaLPP67 (ORCPT ); Tue, 16 Dec 2014 10:58:59 -0500 Received: from mail-pd0-f169.google.com ([209.85.192.169]:59254 "EHLO mail-pd0-f169.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750949AbaLPP65 (ORCPT ); Tue, 16 Dec 2014 10:58:57 -0500 From: Xunlei Pang To: linux-kernel@vger.kernel.org Cc: Peter Zijlstra , Ingo Molnar , Xunlei Pang Subject: [PATCH] sched/fair: Fix the dealing with decay_count in __synchronize_entity_decay() Date: Tue, 16 Dec 2014 23:58:29 +0800 Message-Id: <1418745509-2609-1-git-send-email-pang.xunlei@linaro.org> X-Mailer: git-send-email 1.9.1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 --- 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@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/