Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755434AbbHYIOx (ORCPT ); Tue, 25 Aug 2015 04:14:53 -0400 Received: from mail-pa0-f51.google.com ([209.85.220.51]:34378 "EHLO mail-pa0-f51.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754950AbbHYIOG (ORCPT ); Tue, 25 Aug 2015 04:14:06 -0400 Date: Tue, 25 Aug 2015 16:13:58 +0800 From: Leo Yan To: Wanpeng Li Cc: Ingo Molnar , Peter Zijlstra , linux-kernel@vger.kernel.org Subject: Re: [PATCH] sched: fix tsk->pi_lock isn't held when do_set_cpus_allowed() Message-ID: <20150825081358.GA13299@leoy-linaro> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4053 Lines: 89 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? ;) 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/