Messages in this thread |  | | | Date | Tue, 25 Mar 2008 08:51:06 +0100 | | From | Andi Kleen <> | | Subject | Re: [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
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