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debugobjects: fix lockdep warning

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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>
This commit is contained in:
Vegard Nossum 2008-08-31 23:39:21 +02:00 committed by Thomas Gleixner
parent bef69ea0dc
commit 673d62cc5e
2 changed files with 36 additions and 8 deletions
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13
include/linux/list.h
View file

@ -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) \

31
lib/debugobjects.c
View file

@ -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;
}