Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755970AbaDGWIk (ORCPT ); Mon, 7 Apr 2014 18:08:40 -0400 Received: from mail-la0-f48.google.com ([209.85.215.48]:42841 "EHLO mail-la0-f48.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755919AbaDGWIh (ORCPT ); Mon, 7 Apr 2014 18:08:37 -0400 MIME-Version: 1.0 In-Reply-To: <1396630873-17372-1-git-send-email-sasha.levin@oracle.com> References: <1396630873-17372-1-git-send-email-sasha.levin@oracle.com> From: Bryan Wu Date: Mon, 7 Apr 2014 15:08:15 -0700 Message-ID: Subject: Re: [PATCH] leds: make sure we unregister a trigger only once To: Sasha Levin Cc: "rpurdie@rpsys.net" , Linux LED Subsystem , lkml Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. Thanks, -Bryan > Signed-off-by: Sasha Levin > --- > drivers/leds/led-triggers.c | 5 ++++- > 1 file changed, 4 insertions(+), 1 deletion(-) > > diff --git a/drivers/leds/led-triggers.c b/drivers/leds/led-triggers.c > index df1a7c1..c3734f1 100644 > --- a/drivers/leds/led-triggers.c > +++ b/drivers/leds/led-triggers.c > @@ -219,9 +219,12 @@ void led_trigger_unregister(struct led_trigger *trig) > { > struct led_classdev *led_cdev; > > + if (list_empty_careful(&trig->next_trig)) > + return; > + > /* Remove from the list of led triggers */ > down_write(&triggers_list_lock); > - list_del(&trig->next_trig); > + list_del_init(&trig->next_trig); > up_write(&triggers_list_lock); > > /* Remove anyone actively using this trigger */ > -- > 1.7.10.4 > -- 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/