lkml.org 
[lkml]   [2008]   [Mar]   [25]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [11/14] vcompound: Fallbacks for order 1 stack allocations on IA64 and x86
On Mon, Mar 24, 2008 at 12:53:19PM -0700, Christoph Lameter wrote:
> On Fri, 21 Mar 2008, Andi Kleen wrote:
>
> > The traditional reason this was discouraged (people seem to reinvent
> > variants of this patch all the time) was that there used
> > to be drivers that did __pa() (or equivalent) on stack addresses
> > and that doesn't work with vmalloc pages.
> >
> > I don't know if such drivers still exist, but such a change
> > is certainly not a no-brainer
>
> I thought that had been cleaned up because some arches already have

Someone posted a patch recently that showed that the cdrom layer
does it. Might be more. It is hard to audit a few million lines
of driver code.

> virtually mapped stacks? This could be debugged by testing with
> CONFIG_VFALLBACK_ALWAYS set. Which results in a stack that is always
> vmalloc'ed and thus the driver should fail.

It might be a subtle failure.

Maybe sparse could be taught to check for this if it happens
in a single function? (cc'ing Al who might have some thoughts
on this). Of course if it happens spread out over multiple
functions sparse wouldn't help neither.

-Andi


\
 
 \ /
  Last update: 2008-03-25 08:51    [W:0.122 / U:1.724 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site