From 50db04dd9c74178e68a981a7127c37252ffb3242 Mon Sep 17 00:00:00 2001 From: Vegard Nossum Date: Sun, 15 Jun 2008 00:47:36 +0200 Subject: debugobjects: fix lockdep warning Daniel J Blueman reported: | ======================================================= | [ INFO: possible circular locking dependency detected ] | 2.6.26-rc5-201c #1 | ------------------------------------------------------- | nscd/3669 is trying to acquire lock: | (&n->list_lock){.+..}, at: [] deactivate_slab+0x173/0x1e0 | | but task is already holding lock: | (&obj_hash[i].lock){++..}, at: [] | __debug_object_init+0x2f/0x350 | | which lock already depends on the new lock. There are two locks involved here; the first is a SLUB-local lock, and the second is a debugobjects-local lock. They are basically taken in two different orders: 1. SLUB { debugobjects { ... } } 2. debugobjects { SLUB { ... } } This patch changes pattern #2 by trying to fill the memory pool (e.g. the call into SLUB/kmalloc()) outside the debugobjects lock, so now the two patterns look like this: 1. SLUB { debugobjects { ... } } 2. SLUB { } debugobjects { ... } [ daniel.blueman@gmail.com: pool_lock needs to be taken irq safe in fill_pool ] Reported-by: Daniel J Blueman Signed-off-by: Vegard Nossum Signed-off-by: Thomas Gleixner diff --git a/lib/debugobjects.c b/lib/debugobjects.c index a76a5e1..85b18d7 100644 --- a/lib/debugobjects.c +++ b/lib/debugobjects.c @@ -68,6 +68,7 @@ static int fill_pool(void) { gfp_t gfp = GFP_ATOMIC | __GFP_NORETRY | __GFP_NOWARN; struct debug_obj *new; + unsigned long flags; if (likely(obj_pool_free >= ODEBUG_POOL_MIN_LEVEL)) return obj_pool_free; @@ -81,10 +82,10 @@ static int fill_pool(void) if (!new) return obj_pool_free; - spin_lock(&pool_lock); + spin_lock_irqsave(&pool_lock, flags); hlist_add_head(&new->node, &obj_pool); obj_pool_free++; - spin_unlock(&pool_lock); + spin_unlock_irqrestore(&pool_lock, flags); } return obj_pool_free; } @@ -110,16 +111,13 @@ static struct debug_obj *lookup_object(void *addr, struct debug_bucket *b) } /* - * Allocate a new object. If the pool is empty and no refill possible, - * switch off the debugger. + * Allocate a new object. If the pool is empty, switch off the debugger. */ static struct debug_obj * alloc_object(void *addr, struct debug_bucket *b, struct debug_obj_descr *descr) { struct debug_obj *obj = NULL; - int retry = 0; -repeat: spin_lock(&pool_lock); if (obj_pool.first) { obj = hlist_entry(obj_pool.first, typeof(*obj), node); @@ -141,9 +139,6 @@ repeat: } spin_unlock(&pool_lock); - if (fill_pool() && !obj && !retry++) - goto repeat; - return obj; } @@ -261,6 +256,8 @@ __debug_object_init(void *addr, struct debug_obj_descr *descr, int onstack) struct debug_obj *obj; unsigned long flags; + fill_pool(); + db = get_bucket((unsigned long) addr); spin_lock_irqsave(&db->lock, flags); -- cgit v0.10.2