linux-kernel - Re: Linux 2.6.25-rc2

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Message-ID: <20080219102700.GC14092@elte.hu>
Date:	Tue, 19 Feb 2008 11:27:00 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Pekka Enberg <penberg@...helsinki.fi>
Cc:	Torsten Kaiser <just.for.lkml@...glemail.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>,
	Christoph Lameter <clameter@....com>
Subject: Re: Linux 2.6.25-rc2


* Pekka Enberg <penberg@...helsinki.fi> wrote:

> Mathieu, Christoph is on vacation and I'm not at all that familiar 
> with this cmpxchg_local() optimization, so if you could take a peek at 
> this bug report to see if you can spot something obviously wrong with 
> it, I would much appreciate that.

hm, it's bad for at least one other reason as well (which is probably 
unrelated to this crash):

 /*
  * Currently fastpath is not supported if preemption is enabled.
  */
 #if defined(CONFIG_FAST_CMPXCHG_LOCAL) && !defined(CONFIG_PREEMPT)
 #define SLUB_FASTPATH
 #endif

such !PREEMPT exceptions tend to show "i didnt want to think too hard 
about the preemptible case so just turn it off" thinking.

Also, why isnt this "SLUB_FASTPATH" flag done in the Kconfig space?

	Ingo
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