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    SubjectRe: [PATCH] Do not force shutdown/reboot to boot cpu.
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    On Wed, Apr 10, 2013 at 4:16 AM, Ingo Molnar <mingo@kernel.org> wrote:
    >
    > I think rebooting on the same CPU where we booted up is something worth having in
    > general, as a firmware robustness feature. (assuming the CPU in question is still
    > online)

    Yeah, we've had issues with ACPI in the past, so I do think we should
    always reboot using the BP. Even if it almost certainly works on 99+%
    of all machines on any random CPU.

    The optimal solution would be to just speed up the
    disable_nonboot_cpus() code so much that it isn't an issue. That would
    be good for suspending too, although I guess suspend isn't a big issue
    if you have a thousand CPU's.

    Has anybody checked whether we could do the cpu_down() on non-boot
    CPU's in parallel? Right now we serialize the thing completely, with
    one single

    for_each_online_cpu(cpu) {
    ...

    loop that does a synchrinous _cpu_down() for each CPU. No wonder it
    takes forever. We do __stop_machine() over and over and over again:
    the whole thing is basically O(n**2) in CPU's.

    Linus


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