Commit 673d62cc authored by Vegard Nossum's avatar Vegard Nossum Committed by Thomas Gleixner
Browse files

debugobjects: fix lockdep warning 



Daniel J. Blueman reported:
> =======================================================
> [ INFO: possible circular locking dependency detected ]
> 2.6.27-rc4-224c #1
> -------------------------------------------------------
> hald/4680 is trying to acquire lock:
>  (&n->list_lock){++..}, at: [<ffffffff802bfa26>] add_partial+0x26/0x80
>
> but task is already holding lock:
>  (&obj_hash[i].lock){++..}, at: [<ffffffff8041cfdc>]
> debug_object_free+0x5c/0x120

We fix it by moving the actual freeing to outside the lock (the lock
now only protects the list).

The pool lock is also promoted to irq-safe (suggested by Dan). It's
necessary because free_pool is now called outside the irq disabled
region. So we need to protect against an interrupt handler which calls
debug_object_init().

[tglx@linutronix.de: added hlist_move_list helper to avoid looping
		     through the list twice]

Reported-by: default avatarDaniel J Blueman <daniel.blueman@gmail.com>
Signed-off-by: default avatarVegard Nossum <vegard.nossum@gmail.com>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
parent bef69ea0

include/linux/list.h

+13 −0
Original line number Diff line number Diff line
@@ -619,6 +619,19 @@ static inline void hlist_add_after(struct hlist_node *n, 
		next->next->pprev  = &next->next;

}



/*

 * Move a list from one list head to another. Fixup the pprev

 * reference of the first entry if it exists.

 */

static inline void hlist_move_list(struct hlist_head *old,

				   struct hlist_head *new)

{

	new->first = old->first;

	if (new->first)

		new->first->pprev = &new->first;

	old->first = NULL;

}



#define hlist_entry(ptr, type, member) container_of(ptr,type,member)



#define hlist_for_each(pos, head) \

lib/debugobjects.c

+23 −8
Original line number Diff line number Diff line
@@ -112,6 +112,7 @@ static struct debug_obj *lookup_object(void *addr, struct debug_bucket *b) 


/*

 * Allocate a new object. If the pool is empty, switch off the debugger.

 * Must be called with interrupts disabled.

 */

static struct debug_obj *

alloc_object(void *addr, struct debug_bucket *b, struct debug_obj_descr *descr)
@@ -148,17 +149,18 @@ alloc_object(void *addr, struct debug_bucket *b, struct debug_obj_descr *descr) 
static void free_object(struct debug_obj *obj)

{

	unsigned long idx = (unsigned long)(obj - obj_static_pool);

	unsigned long flags;



	if (obj_pool_free < ODEBUG_POOL_SIZE || idx < ODEBUG_POOL_SIZE) {

		spin_lock(&pool_lock);

		spin_lock_irqsave(&pool_lock, flags);

		hlist_add_head(&obj->node, &obj_pool);

		obj_pool_free++;

		obj_pool_used--;

		spin_unlock(&pool_lock);

		spin_unlock_irqrestore(&pool_lock, flags);

	} else {

		spin_lock(&pool_lock);

		spin_lock_irqsave(&pool_lock, flags);

		obj_pool_used--;

		spin_unlock(&pool_lock);

		spin_unlock_irqrestore(&pool_lock, flags);

		kmem_cache_free(obj_cache, obj);

	}

}
@@ -171,6 +173,7 @@ static void debug_objects_oom(void) 
{

	struct debug_bucket *db = obj_hash;

	struct hlist_node *node, *tmp;

	HLIST_HEAD(freelist);

	struct debug_obj *obj;

	unsigned long flags;

	int i;
@@ -179,11 +182,14 @@ static void debug_objects_oom(void) 


	for (i = 0; i < ODEBUG_HASH_SIZE; i++, db++) {

		spin_lock_irqsave(&db->lock, flags);

		hlist_for_each_entry_safe(obj, node, tmp, &db->list, node) {

		hlist_move_list(&db->list, &freelist);

		spin_unlock_irqrestore(&db->lock, flags);



		/* Now free them */

		hlist_for_each_entry_safe(obj, node, tmp, &freelist, node) {

			hlist_del(&obj->node);

			free_object(obj);

		}

		spin_unlock_irqrestore(&db->lock, flags);

	}

}
@@ -498,8 +504,9 @@ void debug_object_free(void *addr, struct debug_obj_descr *descr) 
		return;

	default:

		hlist_del(&obj->node);

		spin_unlock_irqrestore(&db->lock, flags);

		free_object(obj);

		break;

		return;

	}

out_unlock:

	spin_unlock_irqrestore(&db->lock, flags);
@@ -510,6 +517,7 @@ static void __debug_check_no_obj_freed(const void *address, unsigned long size) 
{

	unsigned long flags, oaddr, saddr, eaddr, paddr, chunks;

	struct hlist_node *node, *tmp;

	HLIST_HEAD(freelist);

	struct debug_obj_descr *descr;

	enum debug_obj_state state;

	struct debug_bucket *db;
@@ -545,11 +553,18 @@ repeat: 
				goto repeat;

			default:

				hlist_del(&obj->node);

				free_object(obj);

				hlist_add_head(&obj->node, &freelist);

				break;

			}

		}

		spin_unlock_irqrestore(&db->lock, flags);



		/* Now free them */

		hlist_for_each_entry_safe(obj, node, tmp, &freelist, node) {

			hlist_del(&obj->node);

			free_object(obj);

		}



		if (cnt > debug_objects_maxchain)

			debug_objects_maxchain = cnt;

	}

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