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Subject2.6.26-rc5: SLUB debug, lockdep warning...
When enabling lockdep + SLUB debugging, I spotted this recursive
lock-acquisition warning [1] when booting, however it doesn't always
pop out.

Let me know if you need further information etc.

Daniel

--- [1]
=======================================================
[ 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.

the existing dependency chain (in reverse order) is:

-> #1 (&obj_hash[i].lock){++..}:
[<ffffffff80278dad>] __lock_acquire+0xbdd/0x1020
[<ffffffff80279255>] lock_acquire+0x65/0x90
[<ffffffff805e1027>] _spin_lock_irqsave+0x47/0x80
[<ffffffff803f9eec>] __debug_check_no_obj_freed+0x6c/0x160
[<ffffffff803f9ff5>] debug_check_no_obj_freed+0x15/0x20
[<ffffffff80296b6d>] free_hot_cold_page+0x10d/0x250
[<ffffffff80296cfb>] free_hot_page+0xb/0x10
[<ffffffff80296d25>] __free_pages+0x25/0x40
[<ffffffff802ba886>] __free_slab+0x96/0x150
[<ffffffff802ba96f>] discard_slab+0x2f/0x50
[<ffffffff802bebe0>] kmem_cache_shrink+0x150/0x280
[<ffffffff8040a8ae>] acpi_os_purge_cache+0x9/0xd
[<ffffffff804217b0>] acpi_purge_cached_objects+0x10/0x38
[<ffffffff80421836>] acpi_initialize_objects+0x49/0x54
[<ffffffff8082ba27>] acpi_init+0x8c/0x221
[<ffffffff80812a98>] kernel_init+0x138/0x320
[<ffffffff80227418>] child_rip+0xa/0x12
[<ffffffffffffffff>] 0xffffffffffffffff
-> #0 (&n->list_lock){.+..}:
[<ffffffff80278c17>] __lock_acquire+0xa47/0x1020
[<ffffffff80279255>] lock_acquire+0x65/0x90
[<ffffffff805e0c41>] _spin_lock+0x31/0x60
[<ffffffff802bab03>] deactivate_slab+0x173/0x1e0
[<ffffffff802bbb12>] __slab_alloc+0x132/0x550
[<ffffffff802bc0d0>] kmem_cache_alloc+0xc0/0xd0
[<ffffffff803fa7f4>] __debug_object_init+0x2b4/0x350
[<ffffffff803fa8ac>] debug_object_init_on_stack+0x1c/0x30
[<ffffffff8026ce59>] hrtimer_init_on_stack+0x29/0x50
[<ffffffff8027ae09>] futex_wait+0x249/0x480
[<ffffffff8027c248>] do_futex+0xb8/0xad0
[<ffffffff8027cd05>] sys_futex+0xa5/0x120
[<ffffffff802264ab>] system_call_after_swapgs+0x7b/0x80
[<ffffffffffffffff>] 0xffffffffffffffff
other info that might help us debug this:

1 lock held by nscd/3669:
#0: (&obj_hash[i].lock){++..}, at: [<ffffffff803fa56f>]
__debug_object_init+0x2f/0x350
stack backtrace:
Pid: 3669, comm: nscd Not tainted 2.6.26-rc5-201c #1

Call Trace:
[<ffffffff80276683>] print_circular_bug_tail+0x83/0x90
[<ffffffff80278c17>] __lock_acquire+0xa47/0x1020
[<ffffffff80279255>] lock_acquire+0x65/0x90
[<ffffffff802bab03>] ? deactivate_slab+0x173/0x1e0
[<ffffffff805e0c41>] _spin_lock+0x31/0x60
[<ffffffff802bab03>] deactivate_slab+0x173/0x1e0
[<ffffffff802bbb12>] __slab_alloc+0x132/0x550
[<ffffffff803fa7f4>] ? __debug_object_init+0x2b4/0x350
[<ffffffff803fa7f4>] ? __debug_object_init+0x2b4/0x350
[<ffffffff802bc0d0>] kmem_cache_alloc+0xc0/0xd0
[<ffffffff803fa7f4>] __debug_object_init+0x2b4/0x350
[<ffffffff803fa8ac>] debug_object_init_on_stack+0x1c/0x30
[<ffffffff8026ce59>] hrtimer_init_on_stack+0x29/0x50
[<ffffffff8027ae09>] futex_wait+0x249/0x480
[<ffffffff80275103>] ? get_lock_stats+0x23/0x70
[<ffffffff8023c815>] ? flat_send_IPI_mask+0x55/0x90
[<ffffffff8023711e>] ? native_smp_send_reschedule+0x2e/0x50
[<ffffffff8024740b>] ? __resched_task+0x6b/0x80
[<ffffffff8024782c>] ? hrtick_start_fair+0x11c/0x160
[<ffffffff80249e20>] ? default_wake_function+0x0/0x10
[<ffffffff8027c248>] do_futex+0xb8/0xad0
[<ffffffff80275103>] ? get_lock_stats+0x23/0x70
[<ffffffff802751e6>] ? lock_release_holdtime+0x66/0x80
[<ffffffff803f246d>] ? __up_read+0x4d/0xb0
[<ffffffff805e1475>] ? _spin_unlock_irqrestore+0x65/0x80
[<ffffffff80277c8f>] ? trace_hardirqs_on+0xbf/0x150
[<ffffffff8022d059>] ? read_tsc+0x9/0x20
[<ffffffff8026f266>] ? getnstimeofday+0x36/0xb0
[<ffffffff8026d04a>] ? ktime_get_ts+0x4a/0x60
[<ffffffff8027cd05>] sys_futex+0xa5/0x120
[<ffffffff802264ab>] system_call_after_swapgs+0x7b/0x80
--
Daniel J Blueman

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