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Subject[34-longterm 087/179] debugobjects: Fix boot crash when kmemleak and debugobjects enabled
From: Marcin Slusarz <>

This is a commit scheduled for the next v2.6.34 longterm release.
If you see a problem with using this for longterm, please comment.

commit 161b6ae0e067e421b20bb35caf66bdb405c929ac upstream.

Order of initialization look like this:
...(lots of other subsystems)...
workqueues (through early initcall)

debugobjects use schedule_work for batch freeing of its data and kmemleak
heavily use debugobjects, so when it comes to freeing and workqueues were
not initialized yet, kernel crashes:

BUG: unable to handle kernel NULL pointer dereference at (null)
IP: [<ffffffff810854d1>] __queue_work+0x29/0x41a
[<ffffffff81085910>] queue_work_on+0x16/0x1d
[<ffffffff81085abc>] queue_work+0x29/0x55
[<ffffffff81085afb>] schedule_work+0x13/0x15
[<ffffffff81242de1>] free_object+0x90/0x95
[<ffffffff81242f6d>] debug_check_no_obj_freed+0x187/0x1d3
[<ffffffff814b6504>] ? _raw_spin_unlock_irqrestore+0x30/0x4d
[<ffffffff8110bd14>] ? free_object_rcu+0x68/0x6d
[<ffffffff8110890c>] kmem_cache_free+0x64/0x12c
[<ffffffff8110bd14>] free_object_rcu+0x68/0x6d
[<ffffffff810b58bc>] __rcu_process_callbacks+0x1b6/0x2d9

because system_wq is NULL.

Fix it by checking if workqueues susbystem was initialized before using.

Signed-off-by: Marcin Slusarz <>
Cc: Catalin Marinas <>
Cc: Tejun Heo <>
Cc: Dipankar Sarma <>
Cc: Paul E. McKenney <>
Signed-off-by: Thomas Gleixner <>
Signed-off-by: Paul Gortmaker <>
lib/debugobjects.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/debugobjects.c b/lib/debugobjects.c
index b862b30..e60bd59 100644
--- a/lib/debugobjects.c
+++ b/lib/debugobjects.c
@@ -197,7 +197,7 @@ static void free_object(struct debug_obj *obj)
* initialized:
if (obj_pool_free > ODEBUG_POOL_SIZE && obj_cache)
- sched = !work_pending(&debug_obj_work);
+ sched = keventd_up() && !work_pending(&debug_obj_work);
hlist_add_head(&obj->node, &obj_pool);

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