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[PATCH] lockdep: avoid lockdep warning in md 

md_open takes ->reconfig_mutex which causes lockdep to complain.  This
(normally) doesn't have deadlock potential as the possible conflict is with a
reconfig_mutex in a different device.

I say "normally" because if a loop were created in the array->member hierarchy
a deadlock could happen.  However that causes bigger problems than a deadlock
and should be fixed independently.

So we flag the lock in md_open as a nested lock.  This requires defining
mutex_lock_interruptible_nested.

Cc: Ingo Molnar <mingo@elte.hu>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
NeilBrown 2006-12-08 02:36:17 -08:00 committed by Linus Torvalds
parent 6796bf54a6
commit d63a5a74de
3 changed files with 12 additions and 1 deletions
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2
drivers/md/md.c
View File

@ -4423,7 +4423,7 @@ static int md_open(struct inode *inode, struct file *file)
mddev_t *mddev = inode->i_bdev->bd_disk->private_data;
int err;
if ((err = mddev_lock(mddev)))
if ((err = mutex_lock_interruptible_nested(&mddev->reconfig_mutex, 1)))
goto out;
err = 0;

2
include/linux/mutex.h
View File

@ -125,8 +125,10 @@ extern int fastcall mutex_lock_interruptible(struct mutex *lock);
#ifdef CONFIG_DEBUG_LOCK_ALLOC
extern void mutex_lock_nested(struct mutex *lock, unsigned int subclass);
extern int mutex_lock_interruptible_nested(struct mutex *lock, unsigned int subclass);
#else
# define mutex_lock_nested(lock, subclass) mutex_lock(lock)
# define mutex_lock_interruptible_nested(lock, subclass) mutex_lock_interruptible(lock)
#endif
/*

9
kernel/mutex.c
View File

@ -206,6 +206,15 @@ mutex_lock_nested(struct mutex *lock, unsigned int subclass)
}
EXPORT_SYMBOL_GPL(mutex_lock_nested);
int __sched
mutex_lock_interruptible_nested(struct mutex *lock, unsigned int subclass)
{
might_sleep();
return __mutex_lock_common(lock, TASK_INTERRUPTIBLE, subclass);
}
EXPORT_SYMBOL_GPL(mutex_lock_interruptible_nested);
#endif
/*