Re: [PATCH] x86 page fault handler not interrupt safe

[Brian Gerst <bgerst@didntduck.org>]

Linus Torvalds wrote:
> 
> On Sat, 5 May 2001, Brian Gerst wrote:
> >
> > Currently the page fault handler on the x86 can get a clobbered value
> > for %cr2 if an interrupt occurs and causes another page fault (interrupt
> > handler touches a vmalloced area for example) before %cr2 is read.
> 
> That should be ok.
> 
> Yes, we'll get a clobbered value, but we'll get a _valid_ clobbered value,
> and we'll just end up doing the fixups twice (and returning to the user
> process that didn't get the page it wanted, which will end up re-doing the
> page fault).
> 
> [ Looks closer.. ]
> 
> Actually, the second time we'd do the fixup we'd be unhappy, because it
> has already been done. That test should probably be removed. Hmm.
> 
> Hmm.. The threading people wanted this same thing. Maybe we should just
> make it so.
> 
>                 Linus

I think it's better to be on the side of correctness.  I designed the
patch to have interrupts disabled for the minimum time possible, so
there should be nearly no impact.

--
					Brian Gerst