From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756300Ab0CJT6H (ORCPT ); Wed, 10 Mar 2010 14:58:07 -0500 Received: from gir.skynet.ie ([193.1.99.77]:43388 "EHLO gir.skynet.ie" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754811Ab0CJT6G (ORCPT ); Wed, 10 Mar 2010 14:58:06 -0500 Date: Wed, 10 Mar 2010 19:57:46 +0000 From: Mel Gorman To: akpm@linux-foundation.org Cc: linux-kernel@vger.kernel.org, Neil Horman , Andi Kleen , "Paul E. McKenney" Subject: mmotm 2010-03-09-19-15: Lot of scheduling while atomic warnings related to RCU Message-ID: <20100310195745.GP4883@csn.ul.ie> References: <201003100342.o2A3gKvA022440@imap1.linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <201003100342.o2A3gKvA022440@imap1.linux-foundation.org> User-Agent: Mutt/1.5.17+20080114 (2008-01-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Mar 09, 2010 at 07:16:03PM -0800, akpm@linux-foundation.org wrote: > The mm-of-the-moment snapshot 2010-03-09-19-15 has been uploaded to > > http://userweb.kernel.org/~akpm/mmotm/ > > and will soon be available at > > git://zen-kernel.org/kernel/mmotm.git > > It contains the following patches against 2.6.34-rc1: > With preempt and sleeping spinlock debugging on, I'm seeing a lot of warnings about scheduling while atomic. Starts off with messages like [ 0.572278] BUG: scheduling while atomic: swapper/1/0x00000002 [ 0.576004] 1 lock held by swapper/1: [ 0.580002] #0: (rcu_read_lock){.+.+.+}, at: [] kobject_uevent_env+0x363/0x4d0 [ 0.600001] Modules linked in: [ 0.608003] Pid: 1, comm: swapper Not tainted 2.6.34-rc1-mm1-vanilla #1 [ 0.612001] Call Trace: [ 0.616005] [] ? __debug_show_held_locks+0x22/0x24 [ 0.620005] [] __schedule_bug+0x77/0x7c [ 0.624004] [] schedule+0xcc/0x723 [ 0.628003] [] schedule_timeout+0x2d/0x28d [ 0.632003] [] ? mark_held_locks+0x4d/0x6b [ 0.636004] [] ? _raw_spin_unlock_irq+0x30/0x5d [ 0.640003] [] ? trace_hardirqs_on_caller+0x110/0x134 [ 0.644003] [] wait_for_common+0xdc/0x152 [ 0.648003] [] ? default_wake_function+0x0/0x14 [ 0.652004] [] wait_for_completion+0x1d/0x1f [ 0.656004] [] call_usermodehelper_exec+0xad/0xfa [ 0.660004] [] ? prepare_usermodehelper_creds+0x136/0x168 [ 0.664003] [] kobject_uevent_env+0x44a/0x4d0 [ 0.668003] [] ? kobject_uevent_env+0x363/0x4d0 [ 0.672003] [] kobject_uevent+0xb/0xd [ 0.676002] [] kset_register+0x37/0x3f [ 0.680004] [] bus_register+0x11f/0x2b1 [ 0.684005] [] platform_bus_init+0x2c/0x44 [ 0.688003] [] driver_init+0x1d/0x29 [ 0.692004] [] kernel_init+0x12e/0x1e3 [ 0.696003] [] kernel_thread_helper+0x4/0x10 [ 0.700004] [] ? restore_args+0x0/0x30 [ 0.704003] [] ? kernel_init+0x0/0x1e3 [ 0.708002] [] ? kernel_thread_helper+0x0/0x10 There are a lot of warnings along these lines during boot. This system did boot *eventually* but it was in obvious trouble. The warnings appear to be all around kobject_uevent_env acquiring the RCU lock and then going to sleep. Most likely candidate problem patches in mmotm are sysctl-fix-up-remaining-references-to-uevent_helper sysctl-fix-up-remaining-references-to-uevent_helper-fix But there are also a whole host of other sysctl-related changes around RCU in there. The changelog implies that these patches are part of some long-lived review process so I didn't delve too deeply. The people most likely to be involved based on comments in the changelog are cc'd. -- Mel Gorman Part-time Phd Student Linux Technology Center University of Limerick IBM Dublin Software Lab