Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754258Ab1E0PXM (ORCPT ); Fri, 27 May 2011 11:23:12 -0400 Received: from na3sys009aog109.obsmtp.com ([74.125.149.201]:46796 "EHLO na3sys009aog109.obsmtp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750922Ab1E0PXK (ORCPT ); Fri, 27 May 2011 11:23:10 -0400 Message-ID: <4DDFC1D6.4010303@ti.com> Date: Fri, 27 May 2011 20:53:02 +0530 From: Santosh Shilimkar User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.2.15) Gecko/20110303 Thunderbird/3.1.9 MIME-Version: 1.0 To: Peter Zijlstra CC: Oleg Nesterov , Marc Zyngier , Frank Rowand , linux-kernel@vger.kernel.org, Yong Zhang , Ingo Molnar , linux-arm-kernel@lists.infradead.org Subject: Re: [BUG] "sched: Remove rq->lock from the first half of ttwu()" locks up on ARM References: <1306343335.21578.65.camel@twins> <1306358128.21578.107.camel@twins> <1306405979.1200.63.camel@twins> <1306407759.27474.207.camel@e102391-lin.cambridge.arm.com> <1306409575.1200.71.camel@twins> <1306412511.1200.90.camel@twins> <20110526154508.GA13788@redhat.com> <1306425584.2497.81.camel@laptop> <1306426148.2497.83.camel@laptop> <20110526170422.GA18413@redhat.com> <1306430264.2497.88.camel@laptop> <1306430633.2497.91.camel@laptop> In-Reply-To: <1306430633.2497.91.camel@laptop> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1468 Lines: 40 Peter, On 5/26/2011 10:53 PM, Peter Zijlstra wrote: > On Thu, 2011-05-26 at 19:17 +0200, Peter Zijlstra wrote: >> On Thu, 2011-05-26 at 19:04 +0200, Oleg Nesterov wrote: >>> On 05/26, Peter Zijlstra wrote: >>>> >>>> @@ -2636,7 +2636,8 @@ try_to_wake_up(struct task_struct *p, unsigned int state, int wake_flags) >>>> * to spin on ->on_cpu if p is current, since that would >>>> * deadlock. >>>> */ >>>> - if (p == current) { >>>> + if (cpu == smp_processor_id()) { >>>> + p->sched_contributes_to_load = 0; >>>> ttwu_queue(p, cpu); >>> >>> Btw. I do not pretend I really understand se->vruntime, but in this >>> case we are doing enqueue_task() without ->task_waking(), however we >>> pass ENQUEUE_WAKING. Is it correct? >> >> No its not, that's the thing that I got wrong the first time and caused >> these pauses. > > We'd end up with something like the below, which isn't too different > from what I've now got queued. > > It has the extra cpu == smp_processor_id() check, but I'm not sure this > whole case is worth the trouble. I could go stick some counters in to > verify how often all this happens I guess. > Are you planning send version of this patch for stable .39 too ? Regards Santosh -- 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/