Messages in this thread Patch in this message | | | Date | Sun, 15 Jun 2008 00:58:26 +0200 | Subject | [PATCH] debugobjects: fix lockdep warning | From | Vegard Nossum <> |
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Hi,
I don't know whether this is truly the Right Fix; if it isn't, feel free to re-use my commit template for when the RF appears... ;-)
Daniel, is there any chance you can try it out? Thanks.
Vegard
From: Vegard Nossum <vegard.nossum@gmail.com> Date: Sun, 15 Jun 2008 00:47:36 +0200 Subject: [PATCH] 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: [<ffffffff802bab03>] deactivate_slab+0x173/0x1e0 | | but task is already holding lock: | (&obj_hash[i].lock){++..}, at: [<ffffffff803fa56f>] | __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 { ... }
Reported-by: Daniel J Blueman <daniel.blueman@gmail.com> Cc: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Vegard Nossum <vegard.nossum@gmail.com> --- lib/debugobjects.c | 10 +++------- 1 files changed, 3 insertions(+), 7 deletions(-)
diff --git a/lib/debugobjects.c b/lib/debugobjects.c index a76a5e1..19acf8c 100644 --- a/lib/debugobjects.c +++ b/lib/debugobjects.c @@ -110,16 +110,13 @@ 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 +138,6 @@ repeat: } spin_unlock(&pool_lock); - if (fill_pool() && !obj && !retry++) - goto repeat; - return obj; } @@ -261,6 +255,8 @@ __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); -- 1.5.4.1
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