Re: early kernel crash when kmemleak is enabled

[Tejun Heo]

Hello,

On Sun, May 15, 2011 at 12:55:05PM +0200, Marcin Slusarz wrote:
> [    0.100047] BUG: unable to handle kernel NULL pointer dereference at           (null)
> [    0.101416] IP: [<ffffffff810854d1>] __queue_work+0x29/0x41a
...
> [    0.110000] Call Trace:
> [    0.110000]  <IRQ> 
> [    0.110000]  [<ffffffff81085910>] queue_work_on+0x16/0x1d
> [    0.110000]  [<ffffffff81085abc>] queue_work+0x29/0x55
> [    0.110000]  [<ffffffff81085afb>] schedule_work+0x13/0x15
> [    0.110000]  [<ffffffff81242de1>] free_object+0x90/0x95
> [    0.110000]  [<ffffffff81242f6d>] debug_check_no_obj_freed+0x187/0x1d3
> [    0.110000]  [<ffffffff814b6504>] ? _raw_spin_unlock_irqrestore+0x30/0x4d
> [    0.110000]  [<ffffffff8110bd14>] ? free_object_rcu+0x68/0x6d
> [    0.110000]  [<ffffffff8110890c>] kmem_cache_free+0x64/0x12c
> [    0.110000]  [<ffffffff8110bd14>] free_object_rcu+0x68/0x6d
> [    0.110000]  [<ffffffff810b58bc>] __rcu_process_callbacks+0x1b6/0x2d9
> [    0.110000]  [<ffffffff81095c9f>] ? tick_handle_periodic+0x1f/0x6c
> [    0.110000]  [<ffffffff810b5a5a>] rcu_process_callbacks+0x7b/0x83
> [    0.110000]  [<ffffffff810733b2>] __do_softirq+0x117/0x207
> [    0.110000]  [<ffffffff810b05d3>] ? handle_irq_event+0x47/0x5c
> [    0.110000]  [<ffffffff814bd0cc>] call_softirq+0x1c/0x30
> [    0.110000]  [<ffffffff81034bc4>] do_softirq+0x38/0x80
> [    0.110000]  [<ffffffff810730ed>] irq_exit+0x4e/0xa0
> [    0.110000]  [<ffffffff8103429a>] do_IRQ+0x97/0xae
> [    0.110000]  [<ffffffff814b6853>] common_interrupt+0x13/0x13

I can reproduce this reliably with your config too.  From a quick
glance, the cause seems to be debug objects using RCU callback
free_object() to free objects, which ends up being called before
workqueue is initialized.  The offending object type is "rcu_head" and
turning off CONFIG_DEBUG_OBJECTS_RCU_HEAD makes the problem go away.

Any ideas on how to fix this?

Thanks.

-- 
tejun
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