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    SubjectRe: [REGRESSION] x86: support for new UV apic
    Andi Kleen wrote:
    > Ingo Molnar <mingo@elte.hu> writes:
    >
    >> * Priit Laes <plaes@plaes.org> wrote:
    >>
    >>> Hey,
    >>>
    >>> I am getting two following warnings (probable one per each CPU core)
    >>> using the latest Linus's git:
    >>>
    >>> WARNING: at arch/x86/kernel/genapic_64.c:86 read_apic_id+0x30/0x62()
    >>> Modules linked in:
    >>> Pid: 1, comm: swapper Not tainted 2.6.25-03563-gf7288b1 #20
    >> thanks - could you check the patch below, does it fix the warnings?
    >
    > I think it would have been better to change the WARN_ON to
    >
    > WARN_ON(preemptible() && num_online_cpus() > 1)

    Hmm , I think you are right , Ingo's patch fixes the warning on boot but now I get one when I reboot the box.

    >
    > Preemption is actually ok here because this runs before the other
    > CPUs are started
    >
    > Alternative patch appended.

    I will test your patch in some minutes.

    >
    > -Andi

    Gabriel

    >
    > ---
    >
    > Don't warn in read_apic_id() when preemptible but only one CPU online.
    >
    > Signed-off-by: Andi Kleen <andi@firstfloor.org>
    >
    > Index: linux/arch/x86/kernel/genapic_64.c
    > ===================================================================
    > --- linux.orig/arch/x86/kernel/genapic_64.c
    > +++ linux/arch/x86/kernel/genapic_64.c
    > @@ -83,7 +83,7 @@ unsigned int read_apic_id(void)
    > {
    > unsigned int id;
    >
    > - WARN_ON(preemptible());
    > + WARN_ON(preemptible() && num_online_cpus() > 1);
    > id = apic_read(APIC_ID);
    > if (uv_system_type >= UV_X2APIC)
    > id |= __get_cpu_var(x2apic_extra_bits);



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