linux-kernel - Re: [RFC] mlock/stack guard interaction fixup

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Message-ID: <1282391770.29609.1223.camel@localhost.localdomain>
Date:	Sat, 21 Aug 2010 12:56:10 +0100
From:	Ian Campbell <ijc@...lion.org.uk>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	linux-kernel@...r.kernel.org, stable@...nel.org,
	stable-review@...nel.org, akpm@...ux-foundation.org,
	alan@...rguk.ukuu.org.uk, Greg KH <gregkh@...e.de>,
	Peter Zijlstra <peterz@...radead.org>,
	Jeremy Fitzhardinge <jeremy@...p.org>
Subject: Re: [RFC] mlock/stack guard interaction fixup

On Fri, 2010-08-20 at 16:59 -0700, Linus Torvalds wrote:
> Ian (and others),
>  here's a three-patch series that uses the doubly linked list to do
> your mlock() case hopefully correctly.

Thanks Linus.

> NOTE! It's untested. The first patch (which is the slightly scary one)
> is tested to some degree, the two other ones I checked that they
> compile, but that's it.

I applied on top of 2.6.35.3 and it fixes the simple test case I posted
yesterday as well as the original issue I was seeing with the Xen
toolstack on 2.6.32.20.

I don't know that they are particularly good tests for this change but I
also ran allmodconfig kernel build and ltp on 2.6.35.3+fixes without
issue. Are there any good mlock heavy workloads?

Out of interest, why is there no guard page for the VM_GROWSUP stack
case? Is it just that the memory layout on PA-RISC makes the stack grows
into the heap scenario impossible?

> I'm not going to apply them to my main tree unless they get testing
> and acks.

Tested-by: Ian Campbell <ijc@...lion.org.uk>

>  And as mentioned, I've not done any of the changes that
> having a vm_prev pointer can allow in other places.
> 
> Comments? Fixes? Braindamage?
> 
>                                Linus

-- 
Ian Campbell

Providence, New Jersey, is one of the few cities where Velveeta cheese
appears on the gourmet shelf.

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