From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wi0-f177.google.com (mail-wi0-f177.google.com [209.85.212.177]) by kanga.kvack.org (Postfix) with ESMTP id 30AFD82BDC for ; Thu, 25 Sep 2014 19:47:03 -0400 (EDT) Received: by mail-wi0-f177.google.com with SMTP id q5so10517114wiv.10 for ; Thu, 25 Sep 2014 16:47:02 -0700 (PDT) Received: from mail-we0-x229.google.com (mail-we0-x229.google.com [2a00:1450:400c:c03::229]) by mx.google.com with ESMTPS id eq7si328700wib.67.2014.09.25.16.47.01 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Thu, 25 Sep 2014 16:47:02 -0700 (PDT) Received: by mail-we0-f169.google.com with SMTP id k48so8744811wev.28 for ; Thu, 25 Sep 2014 16:47:01 -0700 (PDT) Date: Fri, 26 Sep 2014 01:46:59 +0200 From: Frederic Weisbecker Subject: Re: hrtimer deadlock caused by nohz_full Message-ID: <20140925234657.GB14870@lerouge> References: <20140925141425.GA21702@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: owner-linux-mm@kvack.org List-ID: To: Thomas Gleixner Cc: Dave Jones , linux-mm@kvack.org, Peter Zijlstra , LKML On Thu, Sep 25, 2014 at 04:35:49PM +0200, Thomas Gleixner wrote: > On Thu, 25 Sep 2014, Dave Jones wrote: > > > Got this on a box that had been fuzzing for 12 hours or so. > > There's also some timer stuff going on htere, so cc'ing the usual suspects. > > And it's a hrtimer lockup > > > [] ? hrtimer_try_to_cancel+0x58/0x1f0 > > [] ? lock_release+0x1d/0x300 > > [] ? lock_release+0x1d/0x300 > > [] ? hrtimer_try_to_cancel+0x58/0x1f0 > > [] ? lock_release+0x1d/0x300 > > <> [] _raw_spin_unlock_irqrestore+0x24/0x70 > > [] hrtimer_try_to_cancel+0x58/0x1f0 > > [] hrtimer_cancel+0x1a/0x30 > > [] tick_nohz_restart+0x17/0x90 > > [] __tick_nohz_full_check+0xc8/0xe0 > > [] nohz_full_kick_work_func+0xe/0x10 > > [] irq_work_run_list+0x4f/0x70 > > [] irq_work_run+0x2a/0x60 > > [] update_process_times+0x5b/0x70 > > [] tick_sched_handle.isra.21+0x25/0x60 > > [] tick_sched_timer+0x41/0x60 > > [] __run_hrtimer+0x81/0x480 > > [] ? tick_sched_do_timer+0x90/0x90 > > [] hrtimer_interrupt+0x107/0x260 > > [] local_apic_timer_interrupt+0x34/0x60 > > [] smp_apic_timer_interrupt+0x3f/0x60 > > [] apic_timer_interrupt+0x6f/0x80 > > hrtimer_interrupt > tick_sched_timer > tick_sched_handle > update_process_times > irq_work_run > irq_work_run_list > nohz_full_kick_work_func > __tick_nohz_full_check > tick_nohz_restart > hrtimer_cancel > > And that hrtimer_cancel is: > > static void tick_nohz_restart(struct tick_sched *ts, ktime_t now) > { > hrtimer_cancel(&ts->sched_timer); > > Now, that's really bad because we are in the timer callback of > ts->sched_timer. So hrtimer_cancel will loop forever waiting for the > callback to complete. > > Frederic !?!? Right, this patchset fixes it: "[PATCH 0/8] nohz: Fix nohz kick irq work on tick v3" I was about to make the pull request, the branch is acked by peterz. Would you like to pull it? It's all merge window material. git://git.kernel.org/pub/scm/linux/kernel/git/frederic/linux-dynticks.git nohz/fixes-v3 Thanks. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org