linux-kernel - Re: [BUG] Lockdep recursive locking in kmem_cache

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Date:	Fri, 28 Jul 2006 07:53:56 -0700 (PDT)
From:	Christoph Lameter <clameter@....com>
To:	Pekka Enberg <penberg@...helsinki.fi>
cc:	alokk@...softinc.com, tglx@...utronix.de,
	LKML <linux-kernel@...r.kernel.org>, Ingo Molnar <mingo@...e.hu>,
	Arjan van de Ven <arjan@...radead.org>
Subject: Re: [BUG] Lockdep recursive locking in kmem_cache_free

On Fri, 28 Jul 2006, Pekka Enberg wrote:

> > [   57.976447]  [<ffffffff802542fc>] __lock_acquire+0x8cc/0xcb0
> > [   57.976562]  [<ffffffff80254a02>] lock_acquire+0x52/0x70
> > [   57.976675]  [<ffffffff8028f201>] kmem_cache_free+0x141/0x210
> > [   57.976790]  [<ffffffff804a6b74>] _spin_lock+0x34/0x50
> > [   57.976903]  [<ffffffff8028f201>] kmem_cache_free+0x141/0x210
> > [   57.977018]  [<ffffffff8028f388>] slab_destroy+0xb8/0xf0

Huh? _spin_lock calls kmem_cache_free?

>  cache_reap
>  reap_alien	(grabs l3->alien[node]->lock)
>  __drain_alien_cache
>  free_block
>  slab_destroy	(slab management off slab)
>  kmem_cache_free
>  __cache_free
>  cache_free_alien (recursive attempt on l3->alien[node] lock)
> 
> Christoph?

This should not happen. __drain_alien_cache frees node local elements
thus cache_free_alien should not be called. However, if the slab 
management was allocated on a different node from the slab data then we 
may have an issue. However, both slab managemnt and the slab data are 
allocated on the same node (with alloc_pages_node() and kmalloc_node).

If something went wrong with kmalloc_node or alloc_pages_node (fallback?) 
then we may have an issue. Guess we need to look into this some more.
Alok,  have you thought about this issue before?
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