Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755593AbbHYIZG (ORCPT ); Tue, 25 Aug 2015 04:25:06 -0400 Received: from blu004-omc1s14.hotmail.com ([65.55.116.25]:52928 "EHLO BLU004-OMC1S14.hotmail.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751974AbbHYIZA (ORCPT ); Tue, 25 Aug 2015 04:25:00 -0400 X-TMN: [wg4CsUJBxG2XdreJ38nZXL9QTiYN1HeA] X-Originating-Email: [wanpeng.li@hotmail.com] Message-ID: Subject: Re: [PATCH] sched: fix tsk->pi_lock isn't held when do_set_cpus_allowed() To: Leo Yan References: <20150825081358.GA13299@leoy-linaro> CC: Ingo Molnar , Peter Zijlstra , linux-kernel@vger.kernel.org From: Wanpeng Li Date: Tue, 25 Aug 2015 16:24:54 +0800 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.10; rv:38.0) Gecko/20100101 Thunderbird/38.2.0 MIME-Version: 1.0 In-Reply-To: <20150825081358.GA13299@leoy-linaro> Content-Type: text/plain; charset="windows-1252"; format=flowed Content-Transfer-Encoding: 7bit X-OriginalArrivalTime: 25 Aug 2015 08:24:58.0783 (UTC) FILETIME=[87B1E2F0:01D0DF0F] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4504 Lines: 101 On 8/25/15 4:13 PM, Leo Yan wrote: > Hi Wanpeng, > > On Tue, Aug 25, 2015 at 03:59:54PM +0800, Wanpeng Li wrote: >> [ 15.273708] ------------[ cut here ]------------ >> [ 15.274097] WARNING: CPU: 0 PID: 13 at kernel/sched/core.c:1156 do_set_cpus_allowed+0x7e/0x80() >> [ 15.274857] Modules linked in: >> [ 15.275101] CPU: 0 PID: 13 Comm: migration/0 Not tainted 4.2.0-rc1-00049-g25834c7 #2 >> [ 15.275674] 00000000 00000000 d21f1d24 c19228b2 00000000 d21f1d58 c1056a3b c1ba00e4 >> [ 15.276084] 00000000 0000000d c1ba17d8 00000484 c10838be 00000484 c10838be d21e5000 >> [ 15.276084] d2121900 d21e5158 d21f1d68 c1056b12 00000009 00000000 d21f1d7c c10838be >> [ 15.276084] Call Trace: >> [ 15.276084] [] dump_stack+0x4b/0x75 >> [ 15.276084] [] warn_slowpath_common+0x8b/0xc0 >> [ 15.276084] [] ? do_set_cpus_allowed+0x7e/0x80 >> [ 15.276084] [] ? do_set_cpus_allowed+0x7e/0x80 >> [ 15.276084] [] warn_slowpath_null+0x22/0x30 >> [ 15.276084] [] do_set_cpus_allowed+0x7e/0x80 >> [ 15.276084] [] cpuset_cpus_allowed_fallback+0x7c/0x170 >> [ 15.276084] [] ? cpuset_cpus_allowed+0x180/0x180 >> [ 15.276084] [] select_fallback_rq+0x221/0x280 >> [ 15.276084] [] migration_call+0xe3/0x250 >> [ 15.276084] [] notifier_call_chain+0x53/0x70 >> [ 15.276084] [] __raw_notifier_call_chain+0x1e/0x30 >> [ 15.276084] [] cpu_notify+0x28/0x50 >> [ 15.276084] [] take_cpu_down+0x22/0x40 >> [ 15.276084] [] multi_cpu_stop+0xd5/0x140 >> [ 15.276084] [] ? __stop_cpus+0x80/0x80 >> [ 15.276084] [] cpu_stopper_thread+0xbc/0x170 >> [ 15.276084] [] ? preempt_count_sub+0x9/0x50 >> [ 15.276084] [] ? _raw_spin_unlock_irq+0x37/0x50 >> [ 15.276084] [] ? _raw_spin_unlock_irqrestore+0x55/0x70 >> [ 15.276084] [] ? trace_hardirqs_on_caller+0x144/0x1e0 >> [ 15.276084] [] ? cpu_stop_should_run+0x35/0x40 >> [ 15.276084] [] ? preempt_count_sub+0x9/0x50 >> [ 15.276084] [] ? _raw_spin_unlock_irqrestore+0x41/0x70 >> [ 15.276084] [] smpboot_thread_fn+0x174/0x2f0 >> [ 15.276084] [] ? sort_range+0x30/0x30 >> [ 15.276084] [] kthread+0xc4/0xe0 >> [ 15.276084] [] ret_from_kernel_thread+0x21/0x30 >> [ 15.276084] [] ? kthread_create_on_node+0x180/0x180 >> [ 15.276084] ---[ end trace 15f4c86d404693b0 ]--- >> >> After commit (25834c73f93: sched: Fix a race between __kthread_bind() >> and sched_setaffinity()) do_set_cpus_allowed() should be called w/ >> p->pi_lock held, however, it is not true in cpuset path currently. >> >> This patch fix it by holding p->pi_lock in cpuset path. >> >> Signed-off-by: Wanpeng Li >> --- >> kernel/cpuset.c | 4 ++++ >> 1 files changed, 4 insertions(+), 0 deletions(-) >> >> diff --git a/kernel/cpuset.c b/kernel/cpuset.c >> index e414ae9..605ed66 100644 >> --- a/kernel/cpuset.c >> +++ b/kernel/cpuset.c >> @@ -2376,8 +2376,12 @@ void cpuset_cpus_allowed(struct task_struct *tsk, struct cpumask *pmask) >> >> void cpuset_cpus_allowed_fallback(struct task_struct *tsk) >> { >> + unsigned long flags; >> + >> rcu_read_lock(); >> + raw_spin_lock_irqsave(&tsk->pi_lock, flags); >> do_set_cpus_allowed(tsk, task_cs(tsk)->effective_cpus); >> + raw_spin_lock_irqsave(&tsk->pi_lock, flags); > Just curious, Will introduce deadlock after acquire lock twice? ;) Could you point out where acquires lock twice? Regards, Wanpeng Li > > Thanks, > Leo Yan > >> rcu_read_unlock(); >> >> /* >> -- >> 1.7.1 >> >> -- >> 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/ > -- > 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/ -- 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/