Re: [PATCH] x86 page fault handler not interrupt safe
Brian Gerst (firstname.lastname@example.org)
Sun, 06 May 2001 23:54:16 -0400
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.
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.
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