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]

Vegard Nossum committed 18 years ago

Commit 673d62c1 parent bef69ea2 files · +36 −8Browse files

Showing the changes to lib/debugobjects.c (1 of 2 files). Show all

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lib/debugobjects.c+23−8

@@ -112,6 +112,7 @@ static struct debug_obj lookup_object(void addr, struct debug_bucket *b) · 111 unmodified lines
112	112
113	113	/*
114	114	* Allocate a new object. If the pool is empty, switch off the debugger.
	115	+ * Must be called with interrupts disabled.
115	116	*/
116	117	static struct debug_obj *
117	118	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) · 30 unmodified lines
148	149	static void free_object(struct debug_obj *obj)
149	150	{
150	151	unsigned long idx = (unsigned long)(obj - obj_static_pool);
	152	+ unsigned long flags;
151	153
152	154	if (obj_pool_free < ODEBUG_POOL_SIZE \|\| idx < ODEBUG_POOL_SIZE) {
153		− spin_lock(&pool_lock);
	155	+ spin_lock_irqsave(&pool_lock, flags);
154	156	hlist_add_head(&obj->node, &obj_pool);
155	157	obj_pool_free++;
156	158	obj_pool_used--;
157		− spin_unlock(&pool_lock);
	159	+ spin_unlock_irqrestore(&pool_lock, flags);
158	160	} else {
159		− spin_lock(&pool_lock);
	161	+ spin_lock_irqsave(&pool_lock, flags);
160	162	obj_pool_used--;
161		− spin_unlock(&pool_lock);
	163	+ spin_unlock_irqrestore(&pool_lock, flags);
162	164	kmem_cache_free(obj_cache, obj);
163	165	}
164	166	}
@@ -171,6 +173,7 @@ static void debug_objects_oom(void) · 6 unmodified lines
171	173	{
172	174	struct debug_bucket *db = obj_hash;
173	175	struct hlist_node node, tmp;
	176	+ HLIST_HEAD(freelist);
174	177	struct debug_obj *obj;
175	178	unsigned long flags;
176	179	int i;
@@ -179,11 +182,14 @@ static void debug_objects_oom(void) · 2 unmodified lines
179	182
180	183	for (i = 0; i < ODEBUG_HASH_SIZE; i++, db++) {
181	184	spin_lock_irqsave(&db->lock, flags);
182		− hlist_for_each_entry_safe(obj, node, tmp, &db->list, node) {
	185	+ hlist_move_list(&db->list, &freelist);
	186	+ spin_unlock_irqrestore(&db->lock, flags);
	187	+
	188	+ /* Now free them */
	189	+ hlist_for_each_entry_safe(obj, node, tmp, &freelist, node) {
183	190	hlist_del(&obj->node);
184	191	free_object(obj);
185	192	}
186		− spin_unlock_irqrestore(&db->lock, flags);
187	193	}
188	194	}
189	195
@@ -498,8 +504,9 @@ void debug_object_free(void addr, struct debug_obj_descr descr) · 308 unmodified lines
498	504	return;
499	505	default:
500	506	hlist_del(&obj->node);
	507	+ spin_unlock_irqrestore(&db->lock, flags);
501	508	free_object(obj);
502		− break;
	509	+ return;
503	510	}
504	511	out_unlock:
505	512	spin_unlock_irqrestore(&db->lock, flags);
@@ -510,6 +517,7 @@ static void __debug_check_no_obj_freed(const void *address, unsigned long size) · 4 unmodified lines
510	517	{
511	518	unsigned long flags, oaddr, saddr, eaddr, paddr, chunks;
512	519	struct hlist_node node, tmp;
	520	+ HLIST_HEAD(freelist);
513	521	struct debug_obj_descr *descr;
514	522	enum debug_obj_state state;
515	523	struct debug_bucket *db;
@@ -545,11 +553,18 @@ repeat: · 29 unmodified lines
545	553	goto repeat;
546	554	default:
547	555	hlist_del(&obj->node);
548		− free_object(obj);
	556	+ hlist_add_head(&obj->node, &freelist);
549	557	break;
550	558	}
551	559	}
552	560	spin_unlock_irqrestore(&db->lock, flags);
	561	+
	562	+ /* Now free them */
	563	+ hlist_for_each_entry_safe(obj, node, tmp, &freelist, node) {
	564	+ hlist_del(&obj->node);
	565	+ free_object(obj);
	566	+ }
	567	+
553	568	if (cnt > debug_objects_maxchain)
554	569	debug_objects_maxchain = cnt;
555	570	}