Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755641AbaDGWao (ORCPT ); Mon, 7 Apr 2014 18:30:44 -0400 Received: from aserp1040.oracle.com ([141.146.126.69]:16468 "EHLO aserp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754698AbaDGWaj (ORCPT ); Mon, 7 Apr 2014 18:30:39 -0400 Message-ID: <53432701.8020403@oracle.com> Date: Mon, 07 Apr 2014 18:30:25 -0400 From: Sasha Levin User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.4.0 MIME-Version: 1.0 To: Bryan Wu CC: "rpurdie@rpsys.net" , Linux LED Subsystem , lkml Subject: Re: [PATCH] leds: make sure we unregister a trigger only once References: <1396630873-17372-1-git-send-email-sasha.levin@oracle.com> In-Reply-To: X-Enigmail-Version: 1.6 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit X-Source-IP: acsinet21.oracle.com [141.146.126.237] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 04/07/2014 06:08 PM, Bryan Wu wrote: > On Fri, Apr 4, 2014 at 10:01 AM, Sasha Levin wrote: >> Currently, we may attempt to unregister a trigger more than once, for >> example when we receive two consecutive reboot notifications, or when >> we do a regular unregistration plus reboot notification. >> >> This leads to the following error since we try to delete the list node >> twice: >> >> [ 2780.254922] WARNING: CPU: 0 PID: 13764 at lib/list_debug.c:53 __list_del_entry+0x3e/0xe0() >> [ 2780.265559] list_del corruption, ffffffffa5eb6470->next is LIST_POISON1 (dead000000100100) >> [ 2780.271710] Modules linked in: >> [ 2780.274156] CPU: 0 PID: 13764 Comm: kworker/0:2 Tainted: G W 3.14.0-next-20140403-sasha-00012-gef5fa7d-dirty #373 >> [ 2780.283063] Workqueue: events do_poweroff >> [ 2780.285644] 0000000000000009 ffff8800330dbb38 ffffffffa34bfa33 0000000000002fe0 >> [ 2780.291571] ffff8800330dbb88 ffff8800330dbb78 ffffffffa015a37c ffff8800330dbb68 >> [ 2780.296670] ffffffffa5eb6470 0000000000000000 ffffffffa5eb6400 ffffffffa5ad7430 >> [ 2780.299756] Call Trace: >> [ 2780.301530] dump_stack (lib/dump_stack.c:52) >> [ 2780.303802] warn_slowpath_common (kernel/panic.c:418) >> [ 2780.306151] warn_slowpath_fmt (kernel/panic.c:433) >> [ 2780.308156] __list_del_entry (lib/list_debug.c:51 (discriminator 1)) >> [ 2780.310800] list_del (lib/list_debug.c:78) >> [ 2780.313175] led_trigger_unregister (drivers/leds/led-triggers.c:225) >> [ 2780.315599] heartbeat_reboot_notifier (drivers/leds/trigger/ledtrig-heartbeat.c:119) >> [ 2780.317247] notifier_call_chain (kernel/notifier.c:95) >> [ 2780.320014] __blocking_notifier_call_chain (kernel/notifier.c:316) >> [ 2780.323263] blocking_notifier_call_chain (kernel/notifier.c:326) >> [ 2780.326096] kernel_power_off (include/linux/kmod.h:95 kernel/reboot.c:153 kernel/reboot.c:179) >> [ 2780.327883] do_poweroff (kernel/power/poweroff.c:23) >> [ 2780.330748] process_one_work (kernel/workqueue.c:2221 include/linux/jump_label.h:105 include/trace/events/workqueue.h:111 kernel/workqueue.c:2226) >> [ 2780.333027] ? process_one_work (include/linux/workqueue.h:186 kernel/workqueue.c:611 kernel/workqueue.c:638 kernel/workqueue.c:2214) >> [ 2780.335487] process_scheduled_works (include/linux/list.h:188 kernel/workqueue.c:2277) >> [ 2780.337101] worker_thread (kernel/workqueue.c:2352) >> [ 2780.338712] ? rescuer_thread (kernel/workqueue.c:2297) >> [ 2780.341326] kthread (kernel/kthread.c:219) >> [ 2780.343446] ? kthread_create_on_node (kernel/kthread.c:185) >> [ 2780.345733] ret_from_fork (arch/x86/kernel/entry_64.S:555) >> [ 2780.347168] ? kthread_create_on_node (kernel/kthread.c:185) >> >> Prevent it by making sure we don't attempt to unregister a trigger that >> is not in the triggers list. >> > > Looks good to me literally, could you please provide some simple test > case for me? I need verify it on my side. First, make sure you test it on a kernel with list debugging enabled, otherwise there won't be noticeable result unless you end up corrupting something important in the memory. Try calling reboot() and unregistering a device that has a led trigger at the same time (from two different threads) and hope you hit that race. Thanks, Sasha -- 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/