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    SubjectRe: [patch 2/4] introduce the mechanism of disabling cpu hotplug control
    On Tue, 7 Nov 2006 17:40:25 -0800
    "Siddha, Suresh B" <suresh.b.siddha@intel.com> wrote:

    > Add 'cpu_hotplug_no_control' and when set, the hotplug control file("online")
    > will not be added under /sys/devices/system/cpu/cpuX/
    >
    > Next patch doing PCI quirks will use this.
    >

    I don't understand what this (ugly) patch has to do with the overall
    bugfix. We're fixing the APCI initialisation - what does that have to do
    with presenting cpu-hotplug files in sysfs?


    > ---
    >
    > diff --git a/arch/i386/kernel/topology.c b/arch/i386/kernel/topology.c
    > index 07d6da3..9b766e7 100644
    > --- a/arch/i386/kernel/topology.c
    > +++ b/arch/i386/kernel/topology.c
    > @@ -40,14 +40,22 @@ int arch_register_cpu(int num)
    > * restrictions and assumptions in kernel. This basically
    > * doesnt add a control file, one cannot attempt to offline
    > * BSP.
    > + *
    > + * Also certain PCI quirks require to remove this control file
    > + * for all CPU's.
    > */
    > +#ifdef CONFIG_HOTPLUG_CPU
    > + if (!num || cpu_hotplug_no_control)
    > +#else
    > if (!num)
    > +#endif

    This ifdef could be removed

    > cpu_devices[num].cpu.no_control = 1;
    >
    > return register_cpu(&cpu_devices[num].cpu, num);
    > }
    >
    > #ifdef CONFIG_HOTPLUG_CPU
    > +int cpu_hotplug_no_control;
    >
    > void arch_unregister_cpu(int num) {
    > return unregister_cpu(&cpu_devices[num].cpu);
    > diff --git a/include/asm-i386/cpu.h b/include/asm-i386/cpu.h
    > index b1bc7b1..3c5da33 100644
    > --- a/include/asm-i386/cpu.h
    > +++ b/include/asm-i386/cpu.h
    > @@ -13,6 +13,7 @@ struct i386_cpu {
    > extern int arch_register_cpu(int num);
    > #ifdef CONFIG_HOTPLUG_CPU
    > extern void arch_unregister_cpu(int);
    > +extern int cpu_hotplug_no_control;

    via:

    #else
    #define cpu_hotplug_no_control 1

    here.


    But does this variable _have_ to be a negative like this? The code would
    be simpler if it had the opposite sense and was called, say,
    cpu_hotplug_enable_control_file.

    Are these patches considered 2.6.19 material? They look a bit big, ugly
    and scary for that.

    -
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