linux-kernel - Re: [RFC PATCH 02/12] On Tue, 23 Sep 2008, David Miller wrote:

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Message-ID: <48E8D7A5.7060508@linux.intel.com>
Date:	Sun, 05 Oct 2008 08:05:09 -0700
From:	Arjan van de Ven <arjan@...ux.intel.com>
To:	Thomas Gleixner <tglx@...utronix.de>
CC:	Jesse Brandeburg <jesse.brandeburg@...il.com>,
	Jiri Kosina <jkosina@...e.cz>,
	Jesse Barnes <jbarnes@...tuousgeek.org>,
	David Miller <davem@...emloft.net>, jesse.brandeburg@...el.com,
	linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
	kkeil@...e.de, agospoda@...hat.com, david.graham@...el.com,
	bruce.w.allan@...el.com, john.ronciak@...el.com,
	chris.jones@...onical.com, tim.gardner@...onical.com,
	airlied@...il.com, Olaf Kirch <okir@...e.de>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [RFC PATCH 02/12] On Tue, 23 Sep 2008, David Miller wrote:

Thomas Gleixner wrote:
> On Sat, 4 Oct 2008, Jesse Brandeburg wrote:
>>> Exactly. The access to a ro region results in a fault. I have nowhere
>>> seen that trigger, but I can reproduce the trylock() WARN_ON, which
>>> confirms that there is concurrent access to the NVRAM registers. The
>>> backtrace pattern is similar to the one you have seen.
>> are you still getting WARN_ON *with* all the mutex based fixes already applied?
> 
> The WARN_ON triggers with current mainline. Is there any fixlet in
> Linus tree missing ?
> 
>> with the mutex patches in place (without protection patch) we are
>> still reproducing the issue, until we apply the set_memory_ro patch.
> 
> That does not make sense to me. If the memory_ro patch is providing
> _real_ protection then you _must_ run into an access violation. If not,
> then the patch just papers over the real problem in some mysterious
> way.
> 

not if the bad code is doing copy_to_user .... (or similar)
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