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Commit d63a5a74 authored by NeilBrown's avatar NeilBrown Committed by Linus Torvalds
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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: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: default avatarIngo Molnar <mingo@elte.hu>
Signed-off-by: default avatarNeil Brown <neilb@suse.de>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 6796bf54

drivers/md/md.c

+1 −1
Original line number Diff line number Diff line
@@ -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;

include/linux/mutex.h

+2 −0
Original line number Diff line number Diff line
@@ -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



/*

kernel/mutex.c

+9 −0
Original line number Diff line number Diff line
@@ -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



/*