From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S935330AbWKZLTt (ORCPT ); Sun, 26 Nov 2006 06:19:49 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S935342AbWKZLTs (ORCPT ); Sun, 26 Nov 2006 06:19:48 -0500 Received: from ogre.sisk.pl ([217.79.144.158]:2206 "EHLO ogre.sisk.pl") by vger.kernel.org with ESMTP id S935330AbWKZLTr (ORCPT ); Sun, 26 Nov 2006 06:19:47 -0500 From: "Rafael J. Wysocki" To: Greg KH Subject: Re: 2.6.19-rc5-mm2 (end earlier): WARNING at lib/kobject.c:172 kobject_init() on resume from disk Date: Sun, 26 Nov 2006 12:11:02 +0100 User-Agent: KMail/1.9.1 Cc: Andrew Morton , LKML , Andi Kleen References: <200611222207.07143.rjw@sisk.pl> <200611260015.53710.rjw@sisk.pl> <20061125234342.GA31413@kroah.com> In-Reply-To: <20061125234342.GA31413@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200611261211.04044.rjw@sisk.pl> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Sunday, 26 November 2006 00:43, Greg KH wrote: > On Sun, Nov 26, 2006 at 12:15:52AM +0100, Rafael J. Wysocki wrote: > > On Saturday, 25 November 2006 23:20, Rafael J. Wysocki wrote: > > > On Wednesday, 22 November 2006 22:44, Andrew Morton wrote: > > > > On Wed, 22 Nov 2006 22:07:06 +0100 > > > > "Rafael J. Wysocki" wrote: > > > > > > > > > Hi, > > > > > > > > > > I get similar traces on every resume from disk on SMP systems: > > > > > > > > > > WARNING at lib/kobject.c:172 kobject_init() > > > > > > > > > > Call Trace: > > > > > [] dump_trace+0xaa/0x3fd > > > > > [] show_trace+0x3c/0x52 > > > > > [] dump_stack+0x15/0x17 > > > > > [] kobject_init+0x3f/0x8a > > > > > [] kobject_register+0x1a/0x3e > > > > > [] sysdev_register+0x5f/0xec > > > > > [] mce_create_device+0x79/0x103 > > > > > [] mce_cpu_callback+0x2a/0xbd > > > > > [] notifier_call_chain+0x29/0x3e > > > > > [] raw_notifier_call_chain+0x9/0xb > > > > > [] _cpu_up+0xc2/0xd5 > > > > > [] cpu_up+0x2b/0x42 > > > > > [] enable_nonboot_cpus+0x4e/0x9b > > > > > [] snapshot_ioctl+0x1a0/0x5d2 > > > > > [] do_ioctl+0x5e/0x77 > > > > > [] vfs_ioctl+0x256/0x273 > > > > > [] sys_ioctl+0x5f/0x82 > > > > > [] system_call+0x7e/0x83 > > > > > DWARF2 unwinder stuck at system_call+0x7e/0x83 > > > > > Leftover inexact backtrace: > > > > > > > > > > False positive? > > > > > > > > > > > > > Don't know. The changelog in > > > > http://www.kernel.org/pub/linux/kernel/people/gregkh/gregkh-2.6/gregkh-01-driver/kobject-warn.patch > > > > is pretty pathetic. > > > > > > > > Perhaps mce_remove_device() isn't being called. > > > > > > I've added some debugging code into mce_remove_device() which shows that it is > > > being called when the CPU is removed. > > > > > > Investigation continues. > > > > Ah, I think the problem is that the last user of a kobject doesn't decrease > > the refcount in kref_put(), so if the same kobject is registered for the > > second time, the refcount is still one and the warning triggers. > > But the last user of the kobject should cause the kobject to be freed > and disappear. It should not hang around, right? > > Oh yuck, this is a static struct device, one per cpu :( > > > So, it seems, this is a false positive and I think we can get rid of it in the > > following way (tested and works): > > > > --- > > Make mce_remove_device() clean up the kobject in per_cpu(device_mce, cpu) > > after it has been unregistered. > > > > Signed-off-by: Rafael J. Wysocki > > --- > > arch/x86_64/kernel/mce.c | 1 + > > 1 file changed, 1 insertion(+) > > > > Index: linux-2.6.19-rc6-mm1/arch/x86_64/kernel/mce.c > > =================================================================== > > --- linux-2.6.19-rc6-mm1.orig/arch/x86_64/kernel/mce.c 2006-11-25 23:56:08.000000000 +0100 > > +++ linux-2.6.19-rc6-mm1/arch/x86_64/kernel/mce.c 2006-11-26 00:15:34.000000000 +0100 > > @@ -651,6 +651,7 @@ static void mce_remove_device(unsigned i > > sysdev_remove_file(&per_cpu(device_mce,cpu), &attr_tolerant); > > sysdev_remove_file(&per_cpu(device_mce,cpu), &attr_check_interval); > > sysdev_unregister(&per_cpu(device_mce,cpu)); > > + per_cpu(device_mce, cpu).kobj = (struct kobject){ 0 }; > > memset the kobj instead perhaps? Yeah, I guess this copy will work, as > the compiler turns it into a memset. Patch with the memset follows. BTW, it seems to me that the WARN_ON in kref_get will never trigger, will it? Greetings, Rafael --- Make mce_remove_device() clean up the kobject in per_cpu(device_mce, cpu) after it has been unregistered. Signed-off-by: Rafael J. Wysocki --- arch/x86_64/kernel/mce.c | 1 + 1 file changed, 1 insertion(+) Index: linux-2.6.19-rc6-mm1/arch/x86_64/kernel/mce.c =================================================================== --- linux-2.6.19-rc6-mm1.orig/arch/x86_64/kernel/mce.c 2006-11-26 11:31:38.000000000 +0100 +++ linux-2.6.19-rc6-mm1/arch/x86_64/kernel/mce.c 2006-11-26 12:02:10.000000000 +0100 @@ -651,6 +651,7 @@ static void mce_remove_device(unsigned i sysdev_remove_file(&per_cpu(device_mce,cpu), &attr_tolerant); sysdev_remove_file(&per_cpu(device_mce,cpu), &attr_check_interval); sysdev_unregister(&per_cpu(device_mce,cpu)); + memset(&per_cpu(device_mce, cpu).kobj, 0, sizeof(struct kobject)); } /* Get notified when a cpu comes on/off. Be hotplug friendly. */