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    SubjectRe: [PATCH] Fix preemptible lazy mode bug
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    On Thu, 2007-08-23 at 22:46 -0700, Zachary Amsden wrote:
    > I recently sent off a fix for lazy vmalloc faults which can happen under
    > paravirt when lazy mode is enabled. Unfortunately, I jumped the gun a
    > bit on fixing this. I neglected to notice that since the new call to
    > flush the MMU update queue is called from the page fault handler, it can
    > be pre-empted. Both VMI and Xen use per-cpu variables to track lazy
    > mode state, as all previous calls to set, disable, or flush lazy mode
    > happened from a non-preemptable state.

    Hi Zach,

    I don't think this patch does anything. The flush is because we want
    the just-completed "set_pte" to have immediate effect, so if preempt is
    enabled we're already screwed because we can be moved between set_pte
    and the arch_flush_lazy_mmu_mode() call.

    Now, where's the problem caller? By my reading or rc4, vmalloc faults
    are fixed up before enabling interrupts.

    Confused,
    Rusty.


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