From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933159Ab1FACPE (ORCPT ); Tue, 31 May 2011 22:15:04 -0400 Received: from mailout-de.gmx.net ([213.165.64.23]:33059 "HELO mailout-de.gmx.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S933096Ab1FACPC (ORCPT ); Tue, 31 May 2011 22:15:02 -0400 X-Authenticated: #14349625 X-Provags-ID: V01U2FsdGVkX1/tT5ssHm/tSwRf+GGpqn2Qrg9awQeqMevwmuKXtB uDHh8Uek1oidoo Subject: [PATCH] sched, rt: fix rq->rt.pushable_tasks bug in push_rt_task() From: Mike Galbraith To: Steven Rostedt Cc: Hillf Danton , LKML , Yong Zhang , Peter Zijlstra , Ingo Molnar In-Reply-To: <1306854480.11899.29.camel@gandalf.stny.rr.com> References: <1306827397.7536.10.camel@marge.simson.net> <1306854480.11899.29.camel@gandalf.stny.rr.com> Content-Type: text/plain; charset="UTF-8" Date: Wed, 01 Jun 2011 04:14:53 +0200 Message-ID: <1306894493.4791.16.camel@marge.simson.net> Mime-Version: 1.0 X-Mailer: Evolution 2.32.1 Content-Transfer-Encoding: 7bit X-Y-GMX-Trusted: 0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 2011-05-31 at 11:08 -0400, Steven Rostedt wrote: > On Tue, 2011-05-31 at 21:56 +0800, Hillf Danton wrote: > > On Tue, May 31, 2011 at 3:36 PM, Mike Galbraith wrote: > > > On Mon, 2011-05-30 at 21:39 +0800, Hillf Danton wrote: > > >> When pushing, if a pushable task could not be pushed, it is dequeued with no > > >> updating the rt_nr_migratory element of RT run-queue, then rt_nr_migratory is > > >> corrupted, which is fixed by removing the dequeue operation. > > > > > > Hm. I think you're right that this dequeue_pushable_task() call can be > > > removed, at least I didn't see it's reason for existing. I'd word it a > > > bit differently though, and not return 1 unless we really did push. > > > > > > > Hi Mike > > > > Your message shows what is called professional work, but something lost, > > > > > From: Hillf Danton > > > > > > sched, rt: fix rq->rt.pushable_tasks bug in push_rt_task() > > > > > > Do not call dequeue_pushable_task() when failing to push an eligible > > > task, as it remains pushable, merely not at this particular moment. > > > > > > Signed-off-by: Hillf Danton > > > > Signed-off-by: Mike Galbraith > > > > Yeah, Mike, can you remail this adding your SOB too. You can keep > Hillf's SOB as well, since both of you made changes. From: Hillf Danton AuthorDate: Mon, 30 May 2011 21:39:50 +0800 sched, rt: fix rq->rt.pushable_tasks bug in push_rt_task() Do not call dequeue_pushable_task() when failing to push an eligible task, as it remains pushable until either it's cpumask says otherwise, or is selected. It is merely not pushable at this particular moment. Signed-off-by: Hillf Danton Signed-off-by: Mike Galbraith --- kernel/sched_rt.c | 15 ++++++++------- 1 file changed, 8 insertions(+), 7 deletions(-) Index: linux-2.6.40.git/kernel/sched_rt.c =================================================================== --- linux-2.6.40.git.orig/kernel/sched_rt.c +++ linux-2.6.40.git/kernel/sched_rt.c @@ -1378,6 +1378,7 @@ static int push_rt_task(struct rq *rq) { struct task_struct *next_task; struct rq *lowest_rq; + int ret = 0; if (!rq->rt.overloaded) return 0; @@ -1410,7 +1411,7 @@ retry: if (!lowest_rq) { struct task_struct *task; /* - * find lock_lowest_rq releases rq->lock + * find_lock_lowest_rq releases rq->lock * so it is possible that next_task has migrated. * * We need to make sure that the task is still on the same @@ -1420,12 +1421,11 @@ retry: task = pick_next_pushable_task(rq); if (task_cpu(next_task) == rq->cpu && task == next_task) { /* - * If we get here, the task hasn't moved at all, but - * it has failed to push. We will not try again, - * since the other cpus will pull from us when they - * are ready. + * The task hasn't migrated, and is still the next + * eligible task, but we failed to find a run-queue + * to push it to. Do not retry in this case, since + * other cpus will pull from us when ready. */ - dequeue_pushable_task(rq, next_task); goto out; } @@ -1444,6 +1444,7 @@ retry: deactivate_task(rq, next_task, 0); set_task_cpu(next_task, lowest_rq->cpu); activate_task(lowest_rq, next_task, 0); + ret = 1; resched_task(lowest_rq->curr); @@ -1452,7 +1453,7 @@ retry: out: put_task_struct(next_task); - return 1; + return ret; } static void push_rt_tasks(struct rq *rq)