From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933625Ab0BEH0G (ORCPT ); Fri, 5 Feb 2010 02:26:06 -0500 Received: from mx1.redhat.com ([209.132.183.28]:42318 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933310Ab0BEH0D (ORCPT ); Fri, 5 Feb 2010 02:26:03 -0500 Message-ID: <4B6BC87D.1090603@redhat.com> Date: Fri, 05 Feb 2010 15:27:57 +0800 From: Cong Wang User-Agent: Thunderbird 2.0.0.23 (X11/20091001) MIME-Version: 1.0 To: Xiaotian Feng CC: linux-kernel@vger.kernel.org, Tejun Heo , Greg Kroah-Hartman , Peter Zijlstra , "Eric W. Biederman" , Miles Lane , Heiko Carstens , Benjamin Herrenschmidt , Larry Finger , akpm@linux-foundation.org Subject: Re: [Patch v2] sysfs: add lockdep class support to s_active References: <20100205064622.4141.72867.sendpatchset@localhost.localdomain> <7b6bb4a51002042309v3ca1dd0p60b9dbcacdafaee6@mail.gmail.com> In-Reply-To: <7b6bb4a51002042309v3ca1dd0p60b9dbcacdafaee6@mail.gmail.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Xiaotian Feng wrote: > On Fri, Feb 5, 2010 at 2:42 PM, Amerigo Wang wrote: >> Recently we met a lockdep warning from sysfs during s2ram or cpu hotplug. >> As reported by several people, it is something like: >> >> [ 6967.926563] ACPI: Preparing to enter system sleep state S3 >> [ 6967.956156] Disabling non-boot CPUs ... >> [ 6967.970401] >> [ 6967.970408] ============================================= >> [ 6967.970419] [ INFO: possible recursive locking detected ] >> [ 6967.970431] 2.6.33-rc2-git6 #27 >> [ 6967.970439] --------------------------------------------- >> [ 6967.970450] pm-suspend/22147 is trying to acquire lock: >> [ 6967.970460] (s_active){++++.+}, at: [] >> sysfs_hash_and_remove+0x3d/0x4f >> [ 6967.970493] >> [ 6967.970497] but task is already holding lock: >> [ 6967.970506] (s_active){++++.+}, at: [] >> sysfs_get_active_two+0x16/0x36 >> [...] >> >> Eric already provides a patch for this[1], but it still can't fix the >> problem. Based on his work and Peter's suggestion, I write this patch, >> hopefully we can fix the warning completely. >> >> This patch put sysfs s_active into two classes, one is for PM, the other >> is for the rest, so lockdep will distinguish them. > > I think this patch does not hit the root cause, we have a similiar > warning which is not related with PM. > Reported by Nick when he's trying to switch evalator. It is > reproducable with "echo deadline >/sys/block/sdx/queue/scheduler" > while kernel is using cfq. > Well, the four reports that I got are all pm-related, this one is new for me. I think adding another class for io_scheduler would fix this. Thanks. > [ INFO: possible recursive locking detected ] > 2.6.33-rc6 #1 > --------------------------------------------- > sh/889 is trying to acquire lock: > (s_active){++++.+}, at: [<7820a975>] sysfs_addrm_finish+0x27/0x4e > > but task is already holding lock: > (s_active){++++.+}, at: [<7820ab82>] sysfs_get_active_two+0x18/0x3e > > other info that might help us debug this: > 4 locks held by sh/889: > #0: (&buffer->mutex){+.+.+.}, at: [<7820984e>] sysfs_write_file+0x20/0x99 > #1: (s_active){++++.+}, at: [<7820ab82>] sysfs_get_active_two+0x18/0x3e > #2: (s_active){++++.+}, at: [<7820ab91>] sysfs_get_active_two+0x27/0x3e > #3: (&q->sysfs_lock){+.+.+.}, at: [<78289e95>] queue_attr_store+0x2e/0x68 > > stack backtrace: > Pid: 889, comm: sh Not tainted 2.6.33-rc6 #1 > Call Trace: > [<784a6966>] ? printk+0xf/0x11 > [<781752a1>] print_deadlock_bug+0x99/0xa3 > [<781753c6>] check_deadlock+0x11b/0x140 > [<781763e5>] validate_chain+0x4ec/0x4f9 > [<78176a68>] __lock_acquire+0x676/0x6cf > [<78176b64>] lock_acquire+0xa3/0xbc > [<7820a975>] ? sysfs_addrm_finish+0x27/0x4e > [<7820a37a>] sysfs_deactivate+0x6c/0xa4 > [<7820a975>] ? sysfs_addrm_finish+0x27/0x4e > [<7820a975>] sysfs_addrm_finish+0x27/0x4e > [<7820aa3a>] sysfs_remove_dir+0x62/0x72 > [<7829d6dd>] kobject_del+0x11/0x32 > [<78283406>] __elv_unregister_queue+0x18/0x20 > [<78283c66>] elevator_switch+0x6d/0x11b > [<78283d92>] elv_iosched_store+0x7e/0x9b > [<78289eb8>] queue_attr_store+0x51/0x68 > [<78209894>] sysfs_write_file+0x66/0x99 > [<781cd460>] vfs_write+0x8a/0x108 > [<781cd578>] sys_write+0x3c/0x63 > [<78125b90>] sysenter_do_call+0x12/0x36 >