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    SubjectRe: [PATCH] x86: Document the hotplug code is incompatible with x86 irq handling
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    On Friday, 1 June 2007 21:48, Eric W. Biederman wrote:
    > "Rafael J. Wysocki" <rjw@sisk.pl> writes:
    > >> Cool.
    > >>
    > >> My patch does not change the functionality of the code just complains
    > >> very loudly that it is broken.
    > >>
    > >> Further the code is broken at a design level. The code isn't
    > >> problematic the code is impossible. The cpu hotplug code can not be
    > >> fixed on x86 without a redesign of the generic cpu hotplug code.
    > >>
    > >> Suspend does not need to use cpu hotplug because it already gets in
    > >> deep with the drivers, and can stop interrupts at the source. I know
    > >> there was some talk about this doing this earlier, but I don't know if
    > >> anything came of that discussion.
    > >>
    > >> Regardless if you care about this being a problem feel free to fix the
    > >> relevant code so it attempts to do something that the hardware
    > >> actually supports.
    > >>
    > >> But if the suspend needs this code for smp support it is also broken.
    > >
    > > Well, from the functionality point of view, it's not. We have no problems
    > > with it, at least not that I know of.
    >
    > Luck, or enough other issues someone hasn't tracked their problems
    > down to this. On the pure cpu hotplug path I just got a bug
    > report about it not working: http://lkml.org/lkml/2007/5/31/419

    [Apart from what I said in the other message:]

    In the hibernation/suspend code paths we call the CPU hotplug quite late,
    actually right before we turn off local IRQs on the only CPU that is not
    offlined. I think that at this point the majority of interrupt sources should
    have been turned off already.

    Greetings,
    Rafael


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