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authorPeter Zijlstra <a.p.zijlstra@chello.nl>2006-12-06 20:36:13 -0800
committerLinus Torvalds <torvalds@woody.osdl.org>2006-12-07 08:39:32 -0800
commit9a2239b1174bdf0952a21ed328cd74240d2dd173 (patch)
tree04082ce82de232a065436ed588edc56eb47018a0 /drivers/ide/ide.c
parent23a1b2a78705caa2ecaccf8422a1e22eaca59574 (diff)
downloadop-kernel-dev-9a2239b1174bdf0952a21ed328cd74240d2dd173.zip
op-kernel-dev-9a2239b1174bdf0952a21ed328cd74240d2dd173.tar.gz
[PATCH] lockdep: fix ide/proc interaction
rmmod/3080 [HC0[0]:SC0[0]:HE0:SE1] is trying to acquire: (proc_subdir_lock){--..}, at: [<c04a33b0>] remove_proc_entry+0x40/0x191 and this task is already holding: (ide_lock){++..}, at: [<c05651a2>] 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: [<c043c458>] lock_acquire+0x4b/0x6b [<c06129d7>] _spin_lock_irqsave+0x22/0x32 [<c0567870>] ide_intr+0x17/0x1a9 [<c044eb31>] handle_IRQ_event+0x20/0x4d [<c044ebf2>] __do_IRQ+0x94/0xef [<c0406771>] do_IRQ+0x9e/0xbd to a hard-irq-unsafe lock: (proc_subdir_lock){--..} ... which became hard-irq-unsafe at: ... [<c043c458>] lock_acquire+0x4b/0x6b [<c06126ab>] _spin_lock+0x19/0x28 [<c04a32f2>] xlate_proc_name+0x1b/0x99 [<c04a3547>] proc_create+0x46/0xdf [<c04a3642>] create_proc_entry+0x62/0xa5 [<c07c1972>] proc_misc_init+0x1c/0x1d2 [<c07c1844>] proc_root_init+0x4c/0xe9 [<c07ad703>] 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 <a.p.zijlstra@chello.nl> Cc: Alan Cox <alan@lxorguk.ukuu.org.uk> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'drivers/ide/ide.c')
-rw-r--r--drivers/ide/ide.c19
1 files changed, 15 insertions, 4 deletions
diff --git a/drivers/ide/ide.c b/drivers/ide/ide.c
index 287a662..1689076 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);
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