Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752310AbbFYRLp (ORCPT ); Thu, 25 Jun 2015 13:11:45 -0400 Received: from mail-ie0-f175.google.com ([209.85.223.175]:33370 "EHLO mail-ie0-f175.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751764AbbFYRLl (ORCPT ); Thu, 25 Jun 2015 13:11:41 -0400 From: bsegall@google.com To: Cong Wang Cc: linux-kernel@vger.kernel.org, Ingo Molnar , Peter Zijlstra , Cong Wang Subject: Re: [PATCH] sched_fair: test list head instead of list entry in throttle_cfs_rq() References: <1435174907-432-1-git-send-email-xiyou.wangcong@gmail.com> Date: Thu, 25 Jun 2015 10:11:38 -0700 In-Reply-To: <1435174907-432-1-git-send-email-xiyou.wangcong@gmail.com> (Cong Wang's message of "Wed, 24 Jun 2015 12:41:47 -0700") Message-ID: User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.3 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1467 Lines: 42 Cong Wang writes: > 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. > > Cc: Ingo Molnar > Cc: Peter Zijlstra > Signed-off-by: Cong Wang > Signed-off-by: Cong Wang Agreed. Reviewed-by: Ben Segall > --- > 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 40a7fcb..ee91917 100644 > --- a/kernel/sched/fair.c > +++ b/kernel/sched/fair.c > @@ -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 -- 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/