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Commit 64aa348e authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
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lockdep: lock_set_subclass - reset a held lock's subclass 



this can be used to reset a held lock's subclass, for arbitrary-depth
iterated data structures such as trees or lists which have per-node
locks.

Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 5e710e37

include/linux/lockdep.h

+4 −0
Original line number Diff line number Diff line
@@ -300,6 +300,9 @@ extern void lock_acquire(struct lockdep_map *lock, unsigned int subclass, 
extern void lock_release(struct lockdep_map *lock, int nested,

			 unsigned long ip);



extern void lock_set_subclass(struct lockdep_map *lock, unsigned int subclass,

			      unsigned long ip);



# define INIT_LOCKDEP				.lockdep_recursion = 0,



#define lockdep_depth(tsk)	(debug_locks ? (tsk)->lockdep_depth : 0)
@@ -316,6 +319,7 @@ static inline void lockdep_on(void) 


# define lock_acquire(l, s, t, r, c, i)		do { } while (0)

# define lock_release(l, n, i)			do { } while (0)

# define lock_set_subclass(l, s, i)		do { } while (0)

# define lockdep_init()				do { } while (0)

# define lockdep_info()				do { } while (0)

# define lockdep_init_map(lock, name, key, sub)	do { (void)(key); } while (0)

kernel/lockdep.c

+69 −0
Original line number Diff line number Diff line
@@ -2660,6 +2660,55 @@ static int check_unlock(struct task_struct *curr, struct lockdep_map *lock, 
	return 1;

}



static int

__lock_set_subclass(struct lockdep_map *lock,

		    unsigned int subclass, unsigned long ip)

{

	struct task_struct *curr = current;

	struct held_lock *hlock, *prev_hlock;

	struct lock_class *class;

	unsigned int depth;

	int i;



	depth = curr->lockdep_depth;

	if (DEBUG_LOCKS_WARN_ON(!depth))

		return 0;



	prev_hlock = NULL;

	for (i = depth-1; i >= 0; i--) {

		hlock = curr->held_locks + i;

		/*

		 * We must not cross into another context:

		 */

		if (prev_hlock && prev_hlock->irq_context != hlock->irq_context)

			break;

		if (hlock->instance == lock)

			goto found_it;

		prev_hlock = hlock;

	}

	return print_unlock_inbalance_bug(curr, lock, ip);



found_it:

	class = register_lock_class(lock, subclass, 0);

	hlock->class = class;



	curr->lockdep_depth = i;

	curr->curr_chain_key = hlock->prev_chain_key;



	for (; i < depth; i++) {

		hlock = curr->held_locks + i;

		if (!__lock_acquire(hlock->instance,

			hlock->class->subclass, hlock->trylock,

				hlock->read, hlock->check, hlock->hardirqs_off,

				hlock->acquire_ip))

			return 0;

	}



	if (DEBUG_LOCKS_WARN_ON(curr->lockdep_depth != depth))

		return 0;

	return 1;

}



/*

 * Remove the lock to the list of currently held locks in a

 * potentially non-nested (out of order) manner. This is a
@@ -2824,6 +2873,26 @@ static void check_flags(unsigned long flags) 
#endif

}



void

lock_set_subclass(struct lockdep_map *lock,

		  unsigned int subclass, unsigned long ip)

{

	unsigned long flags;



	if (unlikely(current->lockdep_recursion))

		return;



	raw_local_irq_save(flags);

	current->lockdep_recursion = 1;

	check_flags(flags);

	if (__lock_set_subclass(lock, subclass, ip))

		check_chain_key(current);

	current->lockdep_recursion = 0;

	raw_local_irq_restore(flags);

}



EXPORT_SYMBOL_GPL(lock_set_subclass);



/*

 * We are not always called with irqs disabled - do that here,

 * and also avoid lockdep recursion: