linux-kernel - Re: [PATCH] Fix crash in viafb due to 4k stack overflow

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Message-ID: <20081109122515.1deb9ec2@infradead.org>
Date:	Sun, 9 Nov 2008 12:25:15 -0800
From:	Arjan van de Ven <arjan@...radead.org>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Bruno Prémont <bonbons@...ux-vserver.org>,
	JosephChan@....com.tw, <linux-fbdev-devel@...ts.sourceforge.net>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] Fix crash in viafb due to 4k stack overflow

On Sun, 9 Nov 2008 11:36:03 -0800
Andrew Morton <akpm@...ux-foundation.org> wrote:

> On Sun, 9 Nov 2008 20:25:37 +0100 Bruno Pr__mont
> <bonbons@...ux-vserver.org> wrote:
> 
> > The function viafb_cursor() uses 2 stack-variables of CURSOR_SIZE
> > bits; CURSOR_SIZE is defined as (8 * 1024). Using up twice 1k on
> > stack is too much for 4k-stack (though it works with 8k-stacks).
> 
> >  
> >  	if (viacursor.enable)
> 
> Is the ->fb_cursor handler allowed to perform GFP_KERNEL memory
> allocations?  It's never called from atomic contexts?

if it's allowed to do GFP_KERNEL memory allocations the statement that
it works with 8k stacks is a bit overstated... since irq's can come in
and take several KB of stack as well ;)

-- 
Arjan van de Ven 	Intel Open Source Technology Centre
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