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Commit 381a2292 authored by Jarek Poplawski's avatar Jarek Poplawski Committed by Linus Torvalds
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[PATCH] lockdep: more unlock-on-error fixes 



- returns after DEBUG_LOCKS_WARN_ON added in 3 places

- debug_locks checking after lookup_chain_cache() added in
  __lock_acquire()

- locking for testing and changing global variable max_lockdep_depth
  added in __lock_acquire()

From: Ingo Molnar <mingo@elte.hu>

My __acquire_lock() cleanup introduced a locking bug: on SMP systems we'd
release a non-owned graph lock.  Fix this by moving the graph unlock back,
and by leaving the max_lockdep_depth variable update possibly racy.  (we
dont care, it's just statistics)

Also add some minimal debugging code to graph_unlock()/graph_lock(),
which caught this locking bug.

Signed-off-by: default avatarJarek Poplawski <jarkao2@o2.pl>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 898552c9

kernel/lockdep.c

+19 −4
Original line number Diff line number Diff line
@@ -70,6 +70,9 @@ static int graph_lock(void) 


static inline int graph_unlock(void)

{

	if (debug_locks && !__raw_spin_is_locked(&lockdep_lock))

		return DEBUG_LOCKS_WARN_ON(1);



	__raw_spin_unlock(&lockdep_lock);

	return 0;

}
@@ -712,6 +715,9 @@ find_usage_backwards(struct lock_class *source, unsigned int depth) 
	struct lock_list *entry;

	int ret;



	if (!__raw_spin_is_locked(&lockdep_lock))

		return DEBUG_LOCKS_WARN_ON(1);



	if (depth > max_recursion_depth)

		max_recursion_depth = depth;

	if (depth >= RECURSION_LIMIT)
@@ -1293,7 +1299,8 @@ register_lock_class(struct lockdep_map *lock, unsigned int subclass, int force) 
	if (!subclass || force)

		lock->class_cache = class;



	DEBUG_LOCKS_WARN_ON(class->subclass != subclass);

	if (DEBUG_LOCKS_WARN_ON(class->subclass != subclass))

		return NULL;



	return class;

}
@@ -1308,7 +1315,8 @@ static inline int lookup_chain_cache(u64 chain_key, struct lock_class *class) 
	struct list_head *hash_head = chainhashentry(chain_key);

	struct lock_chain *chain;



	DEBUG_LOCKS_WARN_ON(!irqs_disabled());

	if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))

		return 0;

	/*

	 * We can walk it lock-free, because entries only get added

	 * to the hash:
@@ -1394,7 +1402,9 @@ static void check_chain_key(struct task_struct *curr) 
			return;

		}

		id = hlock->class - lock_classes;

		DEBUG_LOCKS_WARN_ON(id >= MAX_LOCKDEP_KEYS);

		if (DEBUG_LOCKS_WARN_ON(id >= MAX_LOCKDEP_KEYS))

			return;



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

							hlock->irq_context))

			chain_key = 0;
@@ -2205,7 +2215,11 @@ static int __lock_acquire(struct lockdep_map *lock, unsigned int subclass, 
			if (!check_prevs_add(curr, hlock))

				return 0;

		graph_unlock();

	}

	} else

		/* after lookup_chain_cache(): */

		if (unlikely(!debug_locks))

			return 0;



	curr->lockdep_depth++;

	check_chain_key(curr);

	if (unlikely(curr->lockdep_depth >= MAX_LOCK_DEPTH)) {
@@ -2214,6 +2228,7 @@ static int __lock_acquire(struct lockdep_map *lock, unsigned int subclass, 
		printk("turning off the locking correctness validator.\n");

		return 0;

	}



	if (unlikely(curr->lockdep_depth > max_lockdep_depth))

		max_lockdep_depth = curr->lockdep_depth;