From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sergey Senozhatsky Subject: [PATCH] Battery: sysfs_remove_battery(): possible circular locking Date: Fri, 5 Aug 2011 03:33:22 +0300 Message-ID: <20110805003322.GA8311@swordfish> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from mail-yx0-f174.google.com ([209.85.213.174]:44719 "EHLO mail-yx0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754268Ab1HEAe2 (ORCPT ); Thu, 4 Aug 2011 20:34:28 -0400 Content-Disposition: inline Sender: linux-acpi-owner@vger.kernel.org List-Id: linux-acpi@vger.kernel.org To: Len Brown Cc: Lan Tianyu , linux-acpi@vger.kernel.org, linux-kernel@vger.kernel.org Commit 9c921c22a7f33397a6774d7fa076db9b6a0fd669 Author: Lan Tianyu ACPI / Battery: Resolve the race condition in the sysfs_remove_battery() introduced battery locking to sysfs_remove_battery(). That lead to a possible deadlock warning: [14818.477170] ======================================================= [14818.477200] [ INFO: possible circular locking dependency detected ] [14818.477221] 3.1.0-dbg-07865-g1280ea8-dirty #668 [14818.477236] ------------------------------------------------------- [14818.477257] s2ram/1599 is trying to acquire lock: [14818.477276] (s_active#8){++++.+}, at: [] sysfs_addrm_finish+0x31/0x5a [14818.477323] [14818.477325] but task is already holding lock: [14818.477350] (&battery->lock){+.+.+.}, at: [] sysfs_remove_battery+0x10/0x4b [battery] [14818.477395] [14818.477397] which lock already depends on the new lock. [...] [14818.479121] stack backtrace: [14818.479148] Pid: 1599, comm: s2ram Not tainted 3.1.0-dbg-07865-g1280ea8-dirty #668 [14818.479175] Call Trace: [14818.479198] [] print_circular_bug+0x293/0x2a4 [14818.479228] [] __lock_acquire+0xfe4/0x164b [14818.479260] [] ? sysfs_addrm_finish+0x31/0x5a [14818.479288] [] lock_acquire+0x138/0x1ac [14818.479316] [] ? sysfs_addrm_finish+0x31/0x5a [14818.479345] [] sysfs_deactivate+0x9b/0xec [14818.479373] [] ? sysfs_addrm_finish+0x31/0x5a [14818.479405] [] sysfs_addrm_finish+0x31/0x5a [14818.479433] [] sysfs_hash_and_remove+0x54/0x77 [14818.479461] [] sysfs_remove_file+0x12/0x14 [14818.479488] [] device_remove_file+0x12/0x14 [14818.479516] [] device_del+0x119/0x17c [14818.479542] [] device_unregister+0xe/0x1a [14818.479570] [] power_supply_unregister+0x23/0x27 [14818.479601] [] sysfs_remove_battery+0x34/0x4b [battery] [14818.479632] [] battery_notify+0x2c/0x3a [battery] [14818.479662] [] notifier_call_chain+0x74/0xa1 [14818.479692] [] __blocking_notifier_call_chain+0x6c/0x89 [14818.479722] [] blocking_notifier_call_chain+0xf/0x11 [14818.479751] [] pm_notifier_call_chain+0x15/0x27 [14818.479770] [] enter_state+0xa7/0xd5 [14818.479782] [] state_store+0xaa/0xc0 [14818.479795] [] ? pm_async_store+0x45/0x45 [14818.479807] [] kobj_attr_store+0x17/0x19 [14818.479820] [] sysfs_write_file+0x103/0x13f [14818.479834] [] vfs_write+0xad/0x13d [14818.479847] [] sys_write+0x45/0x6c [14818.479860] [] system_call_fastpath+0x16/0x1b I've changed `the marker' from `battery->bat.dev' to `battery->bat.name', so the basic idea should remain the same, now we just can release battery->lock more quicker, before device_remove_file() call. Signed-off-by: Sergey Senozhatsky --- drivers/acpi/battery.c | 6 ++++-- 1 files changed, 4 insertions(+), 2 deletions(-) diff --git a/drivers/acpi/battery.c b/drivers/acpi/battery.c index 87c0a8d..398cbfb 100644 --- a/drivers/acpi/battery.c +++ b/drivers/acpi/battery.c @@ -574,15 +574,17 @@ static int sysfs_add_battery(struct acpi_battery *battery) static void sysfs_remove_battery(struct acpi_battery *battery) { mutex_lock(&battery->lock); - if (!battery->bat.dev) { + if (!battery->bat.name) { mutex_unlock(&battery->lock); return; } + battery->bat.name = NULL; + mutex_unlock(&battery->lock); + device_remove_file(battery->bat.dev, &alarm_attr); power_supply_unregister(&battery->bat); battery->bat.dev = NULL; - mutex_unlock(&battery->lock); } /*