On Thursday, May 09, 2013 03:01:21 PM Andrew Morton wrote:
> On Tue, 7 May 2013 09:39:45 -0500 Robin Holt <holt@xxxxxxx> wrote:
>
> > From: "Srivatsa S. Bhat" <srivatsa.bhat@xxxxxxxxxxxxxxxxxx>
> >
> > There are instances in the kernel where we would like to disable
> > CPU hotplug (from sysfs) during some important operation. Today
> > the freezer code depends on this and the code to do it was kinda
> > tailor-made for that.
> >
> > Restructure the code and make it generic enough to be useful for
> > other usecases too.
> >
> > ...
> >
> > --- a/include/linux/cpu.h
> > +++ b/include/linux/cpu.h
> > @@ -141,6 +141,8 @@ static inline void unregister_cpu_notifier(struct notifier_block *nb)
> > }
> > #endif
> >
> > +extern void cpu_hotplug_disable(void);
> > +extern void cpu_hotplug_enable(void);
> > int cpu_up(unsigned int cpu);
> > void notify_cpu_starting(unsigned int cpu);
> > extern void cpu_maps_update_begin(void);
> > @@ -148,6 +150,7 @@ extern void cpu_maps_update_done(void);
> >
> > #else /* CONFIG_SMP */
> >
> > +#define cpu_hotplug_disable() do { } while (0)
> > #define cpu_notifier(fn, pri) do { (void)(fn); } while (0)
> >
>
> Breaks alpha allmodconfig because cpu_hotplug_disable() is absent from
> vmlinux.
>
> cpu_hotplug_disable() doesn't get compiled unless we've defined
> CONFIG_PM_SLEEP_SMP. I cannot begin to imagine what the logic is
> behind that!
I suppose it was only used by suspend/hibernate code paths when this was
introduced.
Thanks,
Rafael
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