linux-kernel - Re: Linux 2.6.20-rc7

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Date:	Wed, 31 Jan 2007 08:04:29 -0800 (PST)
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	PaweÅ Sikora <pluto@...k.net>
cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Christoph Hellwig <hch@....de>,
	Pekka Enberg <penberg@...helsinki.fi>,
	"Siddha, Suresh B" <suresh.b.siddha@...el.com>,
	Martin Peschke <mp3@...ibm.com>, Andrew Morton <akpm@...l.org>,
	Adrian Bunk <bunk@...sta.de>
Subject: Re: Linux 2.6.20-rc7

On Wed, 31 Jan 2007, PaweÅ Sikora wrote:
> 
> The 2.6.20-rcX have the same nasty bug as 2.6.19.x.
> 
> [ an oops inside kmem_get_pages ]
> http://bugzilla.kernel.org/show_bug.cgi?id=7889

Pabel, can you detail more exactly which kernels don't work, and which do?

>From bugzilla:

 - 2.6.18.x does work
 - 2.6.19.2 doesn't work.
 - what about plain 2.6.19?
 - can you please test some of the 2.6.19-rcX kernels? Especially 
   2.6.19-rc1 would be good to test.

Since it apparently already happens in 2.6.19 (but it would be really good 
to know exactly when it starts), and considering _where_ it happens, I'd 
be inclined to blame commit d2e7b7d0: "fix potential stack overflow in 
mm/slab.c" by Suresh. 

When do_tune_cpucache() is called at bootup, I'm not sure how safe it is 
to do the kzalloc() thing.

I've added a number of hopefully appropriate people to the Cc. Guys? 
Apparently it only happens with MEMORY_HOTPLUG (and possibly with just an 
SMP kernel on UP), which probably explains why it's been around without 
people really complaining very loudly. 

		Linus