Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753653AbbFSRvs (ORCPT ); Fri, 19 Jun 2015 13:51:48 -0400 Received: from mail.kernel.org ([198.145.29.136]:37029 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753085AbbFSRvj (ORCPT ); Fri, 19 Jun 2015 13:51:39 -0400 MIME-Version: 1.0 In-Reply-To: <20150617083350.GA2433@linutronix.de> References: <1432056298-18738-1-git-send-email-dave@stgolabs.net> <1432056298-18738-2-git-send-email-dave@stgolabs.net> <20150616192911.GA19500@linutronix.de> <1434484226.1903.19.camel@stgolabs.net> <20150617083350.GA2433@linutronix.de> Date: Fri, 19 Jun 2015 10:51:31 -0700 Message-ID: Subject: Re: [PATCH v2] futex: lower the lock contention on the HB lock during wake up From: Kevin Hilman To: Sebastian Andrzej Siewior Cc: Davidlohr Bueso , Thomas Gleixner , Peter Zijlstra , Ingo Molnar , Steven Rostedt , Mike Galbraith , "Paul E. McKenney" , lkml , Tyler Baker , Olof Johansson , Tony Lindgren , linux-omap , Santosh Shilimkar , Felipe Balbi , Nishanth Menon Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1823 Lines: 39 On Wed, Jun 17, 2015 at 1:33 AM, Sebastian Andrzej Siewior wrote: > wake_futex_pi() wakes the task before releasing the hash bucket lock > (HB). The first thing the woken up task usually does is to acquire the > lock which requires the HB lock. On SMP Systems this leads to blocking > on the HB lock which is released by the owner shortly after. > This patch rearranges the unlock path by first releasing the HB lock and > then waking up the task. > > [bigeasy: redo ontop of lockless wake-queues] > Signed-off-by: Thomas Gleixner > Signed-off-by: Sebastian Andrzej Siewior > --- > * Davidlohr Bueso | 2015-06-16 12:50:26 [-0700]: > >>I prefer having two separate patches, thus keeping their own changelog >>for the change justification. > > okay, here it is on top of #1. A handful of boot test failures on ARM/OMAP were found by kernelci.org in next-20150619[1] and were bisected down to this patch, which hit next-20150619 in the form of commit 881bd58d6e9e (futex: Lower the lock contention on the HB lock during wake up). I confirmed that reverting that patch on top of next-20150619 gets things booting again for the affected platforms. I haven't debugged this any further, but full boot logs are available for the boot failures[2][3] and the linux-omap list and maintainer are Cc'd here to help investigate further if needed. Kevin [1] http://kernelci.org/boot/all/job/next/kernel/next-20150619/ [2] http://storage.kernelci.org/next/next-20150619/arm-multi_v7_defconfig/lab-khilman/boot-omap5-uevm.html [3] http://storage.kernelci.org/next/next-20150619/arm-omap2plus_defconfig/lab-tbaker/boot-omap3-beagle-xm.html -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in Please read the FAQ at http://www.tux.org/lkml/