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: Daniel J Blueman <daniel.blueman@gmail.com>
Signed-off-by: Vegard Nossum <vegard.nossum@gmail.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
diff --git a/lib/debugobjects.c b/lib/debugobjects.c
index 45a6bde..e3ab374 100644
--- a/lib/debugobjects.c
+++ b/lib/debugobjects.c
@@ -112,6 +112,7 @@
/*
* 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 @@
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 @@
{
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 @@
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 @@
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 @@
{
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 @@
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;
}