From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756032Ab0IUONn (ORCPT ); Tue, 21 Sep 2010 10:13:43 -0400 Received: from hera.kernel.org ([140.211.167.34]:46444 "EHLO hera.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754647Ab0IUONm (ORCPT ); Tue, 21 Sep 2010 10:13:42 -0400 Date: Tue, 21 Sep 2010 14:13:01 GMT From: tip-bot for Suresh Siddha Cc: linux-kernel@vger.kernel.org, hpa@zytor.com, mingo@redhat.com, a.p.zijlstra@chello.nl, suresh.b.siddha@intel.com, tglx@linutronix.de, mingo@elte.hu Reply-To: mingo@redhat.com, hpa@zytor.com, linux-kernel@vger.kernel.org, a.p.zijlstra@chello.nl, suresh.b.siddha@intel.com, tglx@linutronix.de, mingo@elte.hu In-Reply-To: <1284400941.2684.19.camel@sbsiddha-MOBL3.sc.intel.com> References: <1284400941.2684.19.camel@sbsiddha-MOBL3.sc.intel.com> To: linux-tip-commits@vger.kernel.org Subject: [tip:sched/urgent] sched: Fix nohz balance kick Message-ID: Git-Commit-ID: f6c3f1686e7ec1dd8725a9a3dcb857dfd0c7a5bf X-Mailer: tip-git-log-daemon MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.2.3 (hera.kernel.org [127.0.0.1]); Tue, 21 Sep 2010 14:13:03 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: f6c3f1686e7ec1dd8725a9a3dcb857dfd0c7a5bf Gitweb: http://git.kernel.org/tip/f6c3f1686e7ec1dd8725a9a3dcb857dfd0c7a5bf Author: Suresh Siddha AuthorDate: Mon, 13 Sep 2010 11:02:21 -0700 Committer: Ingo Molnar CommitDate: Tue, 21 Sep 2010 13:50:50 +0200 sched: Fix nohz balance kick There's a situation where the nohz balancer will try to wake itself: cpu-x is idle which is also ilb_cpu got a scheduler tick during idle and the nohz_kick_needed() in trigger_load_balance() checks for rq_x->nr_running which might not be zero (because of someone waking a task on this rq etc) and this leads to the situation of the cpu-x sending a kick to itself. And this can cause a lockup. Avoid this by not marking ourself eligible for kicking. Signed-off-by: Suresh Siddha Signed-off-by: Peter Zijlstra LKML-Reference: <1284400941.2684.19.camel@sbsiddha-MOBL3.sc.intel.com> Signed-off-by: Ingo Molnar --- kernel/sched_fair.c | 2 +- 1 files changed, 1 insertions(+), 1 deletions(-) diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c index a171138..db3f674 100644 --- a/kernel/sched_fair.c +++ b/kernel/sched_fair.c @@ -3630,7 +3630,7 @@ static inline int nohz_kick_needed(struct rq *rq, int cpu) if (time_before(now, nohz.next_balance)) return 0; - if (!rq->nr_running) + if (rq->idle_at_tick) return 0; first_pick_cpu = atomic_read(&nohz.first_pick_cpu);