From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1030320AbWJSIfs (ORCPT ); Thu, 19 Oct 2006 04:35:48 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1030321AbWJSIfs (ORCPT ); Thu, 19 Oct 2006 04:35:48 -0400 Received: from mx.go2.pl ([193.17.41.41]:51682 "EHLO poczta.o2.pl") by vger.kernel.org with ESMTP id S1030320AbWJSIfr (ORCPT ); Thu, 19 Oct 2006 04:35:47 -0400 Date: Thu, 19 Oct 2006 10:40:51 +0200 From: Jarek Poplawski To: Peter Zijlstra Cc: linux-kernel@vger.kernel.org, Andrew Morton , Alan Cox Subject: Re: [PATCH] lockdep: fix ide/proc interaction Message-ID: <20061019084051.GB1872@ff.dom.local> Mail-Followup-To: Jarek Poplawski , Peter Zijlstra , linux-kernel@vger.kernel.org, Andrew Morton , Alan Cox Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1161197380.3036.73.camel@taijtu> User-Agent: Mutt/1.4.2.2i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On 18-10-2006 20:49, Peter Zijlstra wrote: > rmmod/3080 [HC0[0]:SC0[0]:HE0:SE1] is trying to acquire: > (proc_subdir_lock){--..}, at: [] remove_proc_entry+0x40/0x191 > > and this task is already holding: > (ide_lock){++..}, at: [] ide_unregister_subdriver+0x39/0xc8 > which would create a new lock dependency: > (ide_lock){++..} -> (proc_subdir_lock){--..} > > but this new dependency connects a hard-irq-safe lock: > (ide_lock){++..} > ... which became hard-irq-safe at: > [] lock_acquire+0x4b/0x6b > [] _spin_lock_irqsave+0x22/0x32 > [] ide_intr+0x17/0x1a9 > [] handle_IRQ_event+0x20/0x4d > [] __do_IRQ+0x94/0xef > [] do_IRQ+0x9e/0xbd > > to a hard-irq-unsafe lock: > (proc_subdir_lock){--..} > ... which became hard-irq-unsafe at: > ... [] lock_acquire+0x4b/0x6b > [] _spin_lock+0x19/0x28 > [] xlate_proc_name+0x1b/0x99 > [] proc_create+0x46/0xdf > [] create_proc_entry+0x62/0xa5 > [] proc_misc_init+0x1c/0x1d2 > [] proc_root_init+0x4c/0xe9 > [] start_kernel+0x294/0x3b3 > [<00000000>] 0x0 > > Move ide_remove_proc_entries() out from under ide_lock; there is nothing > that indicates that this is needed. > > In specific, the call to ide_add_proc_entries() is unprotected, and there > is nothing else in the file using the respective ->proc fields. Also the > lock order around destroy_proc_ide_interface() suggests this. > > Signed-off-by: Peter Zijlstra > --- > drivers/ide/ide.c | 19 +++++++++++++++---- > 1 file changed, 15 insertions(+), 4 deletions(-) > > Index: linux-2.6/drivers/ide/ide.c > =================================================================== > --- linux-2.6.orig/drivers/ide/ide.c > +++ linux-2.6/drivers/ide/ide.c > @@ -973,8 +973,8 @@ ide_settings_t *ide_find_setting_by_name > * @drive: drive > * > * Automatically remove all the driver specific settings for this > - * drive. This function may sleep and must not be called from IRQ > - * context. The caller must hold ide_setting_sem. > + * drive. This function may not be called from IRQ context. The > + * caller must hold ide_setting_sem. > */ > > static void auto_remove_settings (ide_drive_t *drive) > @@ -1874,11 +1874,22 @@ void ide_unregister_subdriver(ide_drive_ > { > unsigned long flags; > > - down(&ide_setting_sem); > - spin_lock_irqsave(&ide_lock, flags); > #ifdef CONFIG_PROC_FS > ide_remove_proc_entries(drive->proc, driver->proc); But now: > (proc_subdir_lock){--..}, at: [] remove_proc_entry+0x40/0x191 is taken here with irqs and bhs enabled (btw. this: {--..} looks as if it wasn't called from here with spin_lock_irqsave?) IMHO it is hard to believe this lock isn't anywhere used in hard or soft irq context so probably local_irq_disable/enable or local_bh_disable/enable is needed around this. > #endif > + down(&ide_setting_sem); > + spin_lock_irqsave(&ide_lock, flags); > + /* > + * ide_setting_sem protects the settings list > + * ide_lock protects the use of settings > + * > + * so we need to hold both, ide_settings_sem because we want to > + * modify the settings list, and ide_lock because we cannot take > + * a setting out that is being used. > + * > + * OTOH both ide_{read,write}_setting are only ever used under > + * ide_setting_sem. > + */ > auto_remove_settings(drive); But why auto_remove_settings and __ide_remove_setting comments don't mention this ide_lock? > spin_unlock_irqrestore(&ide_lock, flags); > up(&ide_setting_sem); > Regards, Jarek P.