From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-we0-f179.google.com (mail-we0-f179.google.com [74.125.82.179]) by kanga.kvack.org (Postfix) with ESMTP id 3B4F16B0036 for ; Thu, 25 Sep 2014 10:35:53 -0400 (EDT) Received: by mail-we0-f179.google.com with SMTP id u56so153969wes.38 for ; Thu, 25 Sep 2014 07:35:52 -0700 (PDT) Received: from Galois.linutronix.de (Galois.linutronix.de. [2001:470:1f0b:db:abcd:42:0:1]) by mx.google.com with ESMTPS id xt8si2991154wjb.55.2014.09.25.07.35.51 for (version=TLSv1.2 cipher=RC4-SHA bits=128/128); Thu, 25 Sep 2014 07:35:52 -0700 (PDT) Date: Thu, 25 Sep 2014 16:35:49 +0200 (CEST) From: Thomas Gleixner Subject: Re: hrtimer deadlock caused by nohz_full In-Reply-To: <20140925141425.GA21702@redhat.com> Message-ID: References: <20140925141425.GA21702@redhat.com> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org List-ID: To: Dave Jones Cc: linux-mm@kvack.org, Frederic Weisbecker , Peter Zijlstra , LKML 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 !?!? Thanks, tglx -- 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