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    SubjectRe: [patch 1/2] x86_64 page fault NMI-safe
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    On Fri, 2010-07-16 at 14:00 +0200, Frederic Weisbecker wrote:
    > On Thu, Jul 15, 2010 at 07:51:55AM -0700, Linus Torvalds wrote:

    >
    > Such new page table created that might race is only about top level page
    > right? Otherwise it wouldn't race since the top level entries are shared
    > and then updates inside lower level pages are naturally propagated, if
    > I understood you well.
    >
    > So, if only top level pages that gets added can generate such lazily
    > mapping update, I wonder why I experienced this fault everytime with
    > my patches.
    >
    > I allocated 8192 bytes per cpu in a x86-32 system that has only 2 GB.
    > I doubt there is a top level page table update there at this time with
    > such a small amount of available memory. But still it faults once on
    > access.
    >
    > I have troubles to visualize the race and the problem here.
    >

    A few trace_printks and a tracing_off() on fault would probably show
    exactly what was happening ;-)

    -- Steve




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