Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751593AbaDZIij (ORCPT ); Sat, 26 Apr 2014 04:38:39 -0400 Received: from mail-ee0-f43.google.com ([74.125.83.43]:41417 "EHLO mail-ee0-f43.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751522AbaDZIiP (ORCPT ); Sat, 26 Apr 2014 04:38:15 -0400 Message-ID: <1398501491.12941.5.camel@marge.simpson.net> Subject: Re: [ANNOUNCE] 3.14-rt1 From: Mike Galbraith To: Sebastian Andrzej Siewior Cc: linux-rt-users , LKML , Thomas Gleixner , rostedt@goodmis.org, John Kacur Date: Sat, 26 Apr 2014 10:38:11 +0200 In-Reply-To: <1398411635.11930.45.camel@marge.simpson.net> References: <20140411185739.GA6644@linutronix.de> <1397918766.5436.16.camel@marge.simpson.net> <1398411635.11930.45.camel@marge.simpson.net> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.2.3 Content-Transfer-Encoding: 7bit Mime-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 2014-04-25 at 09:40 +0200, Mike Galbraith wrote: > Hotplug can still deadlock in rt trees too, and will if you beat it > hard. Box actually deadlocks like so. CPU3 boot.kdump sys_wait4 do_wait read_lock(&tasklist_lock) rt_read_lock __rt_spin_lock(lock) migrate_disable() pin_current_cpu() if (hp->grab_lock) { preempt_enable(); <== hmm hotplug_lock(hp); hp = &__get_cpu_var(hotplug_pcp); <== hmm struct hotplug_pcp { unplug = 0xffff8800b7d0e540, sync_tsk = 0x0, refcount = 0, <== hmm grab_lock = 1, ... lock = { ... owner = 0xffff8802039f0001, stress-cpu-hotplug_stress.sh?!? <=== he's way over yonder. Yo, dude, would you please NOT take percpu locks with you? CPU0 stress-cpu-hotplug_stress.sh sysfs_write_file dev_attr_store online_store device_offline cpu_subsys_offline cpu_down _cpu_down cpu_hotplug_begin mutex_lock(&cpu_hotplug.lock); ... check_for_tasks write_lock_irq(&tasklist_lock); held by CPU3 boot.kdump over there ===> CPU0 kworker/0:0 cpuset_hotplug_workfn+0x23e/0x380 rebuild_sched_domains+0x15/0x30 rebuild_sched_domains_locked+0x17/0x80 get_online_cpus+0x35/0x50 mutex_lock(&cpu_hotplug.lock); held by stress-cpu-hotplug_stress.sh twiddle twiddle twiddle... INFO: task kworker/0:0:4 blocked for more than 120 seconds. -- 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/