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    SubjectRe: ptrace && fpu_lazy_restore
    On Sun, Apr 15, 2012 at 4:42 PM, Linus Torvalds
    <> wrote:
    > That one is done by design. That fpu_counter=0 in copy_thread() is
    > there explicitly to avoid the problem. Although it's possible that we
    > should reset last_cpu instead. However, that line was actually added
    > before the lazy thing - see commit cea20ca3f318.

    Put another way: I do think it would be a good idea to do the "reset
    last_cpu" in copy_thread() too. It doesn't really cost us anything,
    and it's cleaner to always just make sure that last_cpu is "valid"
    (even if the fpu_owner_task is *also* used to invalidate it, and even
    if we never use the lazy restore if fpu_counter is zero and thus
    fpu.preload isn't set).


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