linux-kernel - Re: [PATCH] Don't mlock guardpage if the stack is growing up

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Message-ID: <BANLkTim7ATRyJ2NvoCj4Sv=7CLizKMd_WA@mail.gmail.com>
Date:	Mon, 9 May 2011 15:31:42 -0700
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	James Bottomley <James.Bottomley@...senpartnership.com>
Cc:	Mikulas Patocka <mikulas@...ax.karlin.mff.cuni.cz>,
	Tony Luck <tony.luck@...el.com>,
	Fenghua Yu <fenghua.yu@...el.com>,
	Hugh Dickins <hughd@...gle.com>, linux-kernel@...r.kernel.org,
	linux-parisc@...r.kernel.org,
	Michel Lespinasse <walken@...gle.com>,
	Oleg Nesterov <oleg@...hat.com>, linux-ia64@...r.kernel.org
Subject: Re: [PATCH] Don't mlock guardpage if the stack is growing up

On Mon, May 9, 2011 at 3:19 PM, James Bottomley
<James.Bottomley@...senpartnership.com> wrote:
>
> So I can test the patch, if you tell me how.  I don't use lvm2, so it
> would have to be a simple test case.

Something like the attached. Run it as root (it needs root just for
the mlockall), and see whether the stack it shows changes.

With current kernels, I think the stack expands by one page during the
mlockall (for STACK_GROWSUP), with the patch it shouldn't.

                   Linus

View attachment "t.c" of type "text/x-csrc" (400 bytes)