linux-kernel - Re: SLOB lockup (was: Re: [tip:core/locking] lockdep: annotate reclaim context (__GFP

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Date:	Sun, 15 Mar 2009 10:47:04 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Nick Piggin <nickpiggin@...oo.com.au>,
	Thomas Gleixner <tglx@...utronix.de>
Cc:	linux-tip-commits@...r.kernel.org, Nick Piggin <npiggin@...e.de>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Pekka Enberg <penberg@...helsinki.fi>,
	Matt Mackall <mpm@...enic.com>, linux-kernel@...r.kernel.org,
	hpa@...or.com, mingo@...hat.com
Subject: Re: SLOB lockup (was: Re: [tip:core/locking] lockdep: annotate
	reclaim context (__GFP_NOFS), fix SLOB)


* Nick Piggin <nickpiggin@...oo.com.au> wrote:

> On Sunday 15 March 2009 17:48:18 Ingo Molnar wrote:
> 
> > > Cc: Nick Piggin <npiggin@...e.de>
> > > Cc: Peter Zijlstra <a.p.zijlstra@...llo.nl>
> > > LKML-Reference: <20090128135457.350751756@...llo.nl>
> > > Signed-off-by: Ingo Molnar <mingo@...e.hu>
> >
> > and with this fixed, and with SLOB now being tested in -tip, the
> > new lockdep assert attached below (followed by a real lockup)
> > pops up.
> >
> > Seems like a genuine SLOB bug, probably present upstream as
> > well.
> 
> Hmmf. debugobjects calls back into the slab allocator from the 
> page allocator. The following patch would improve SLOB, but I 
> think it would be a good idea to avoid a dependency in that 
> direction. Can debugobjects defer this freeing?

dunno - that's a question for Thomas.

this lockup does not trigger under any of the other allocators.

	Ingo
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