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

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Date:	Sun, 22 Aug 2010 08:33:06 +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 Sun, 2010-08-22 at 07:57 +0100, Ian Campbell wrote:
> On Sat, 2010-08-21 at 08:48 -0700, Linus Torvalds wrote:
> > On Sat, Aug 21, 2010 at 4:56 AM, Ian Campbell <ijc@...lion.org.uk> wrote:
> > >
> > > 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?
> > 
> > mlock itself isn't very interesting, I think more interesting is
> > testing that the doubly linked list handles all the cases correctly.
> > Something that splits mappings, unmaps partial ones etc etc. Running
> > something like Electric Fence is probably a good idea.
> 
> EF_DISABLE_BANNER=1 EF_ALLOW_MALLOC_0=1 LD_PRELOAD=libefence.so.0.0 make
> 
> craps out pretty quickly with:
> 
>           CC      init/main.o
>         
>         ElectricFence Exiting: mprotect() failed: Cannot allocate memory
>         make[1]: *** [init/main.o] Error 255
>         make: *** [init] Error 2
> 
> but it does that with 2.6.35.3, 2.6.35.2, 2.6.35.1 and 2.6.35 too so it
> doesn't seem to be breakage relating to any of the stack guard stuff

I increased the vm.max_map_count sysctl and now things are rolling
along. Will let you know how I get on.

-- 
Ian Campbell

Arithmetic:
	An obscure art no longer practiced in the world's developed countries.

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