From mboxrd@z Thu Jan 1 00:00:00 1970 From: Peter Zijlstra Subject: [PATCH] lockdep: fix ide/proc interaction Date: Wed, 18 Oct 2006 20:49:40 +0200 Message-ID: <1161197380.3036.73.camel@taijtu> Mime-Version: 1.0 Content-Type: text/plain Content-Transfer-Encoding: 7bit Return-path: Received: from amsfep17-int.chello.nl ([213.46.243.15]:42931 "EHLO amsfep16-int.chello.nl") by vger.kernel.org with ESMTP id S1422789AbWJRStM (ORCPT ); Wed, 18 Oct 2006 14:49:12 -0400 Sender: linux-ide-owner@vger.kernel.org List-Id: linux-ide@vger.kernel.org To: linux-kernel , B.Zolnierkiewicz@elka.pw.edu.pl, linux-ide@vger.kernel.org Cc: Andrew Morton , Alan Cox 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); #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); spin_unlock_irqrestore(&ide_lock, flags); up(&ide_setting_sem);