debugobjects: fix lockdep warning

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 { ... }

[ daniel.blueman@gmail.com: pool_lock needs to be taken irq safe in fill_pool ]

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>