From 9a2239b1174bdf0952a21ed328cd74240d2dd173 Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Wed, 6 Dec 2006 20:36:13 -0800 Subject: [PATCH] [PATCH] lockdep: fix ide/proc interaction 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 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. Alan sayeth: proc_ide_write_settings walks the setting list under ide_setting_sem, read ditto. remove_proc_entry is doing proc side housekeeping. Looks fine to me, although that old code is such a mess anything could be going on. Signed-off-by: Peter Zijlstra Cc: Alan Cox Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- drivers/ide/ide.c | 19 +++++++++++++++---- 1 file changed, 15 insertions(+), 4 deletions(-) diff --git a/drivers/ide/ide.c b/drivers/ide/ide.c index 287a66201150..16890769dca6 100644 --- a/drivers/ide/ide.c +++ b/drivers/ide/ide.c @@ -973,8 +973,8 @@ ide_settings_t *ide_find_setting_by_name (ide_drive_t *drive, char *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_t *drive, ide_driver_t *driver) { 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); -- 2.20.1