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'll stick this in there and see what happens.
--- a/include/linux/cpu.h~cpu-hotplug-provide-a-generic-helper-to-disable-enable-cpu-hotplug-fix
+++ a/include/linux/cpu.h
@@ -141,8 +141,6 @@ static inline void unregister_cpu_notifi
}
#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);
@@ -150,7 +148,6 @@ 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)
static inline int register_cpu_notifier(struct notifier_block *nb)
@@ -171,6 +168,15 @@ static inline void cpu_maps_update_done(
}
#endif /* CONFIG_SMP */
+
+#ifdef CONFIG_PM_SLEEP_SMP
+extern void cpu_hotplug_enable(void);
+extern void cpu_hotplug_disable(void);
+#else
+#define cpu_hotplug_enable() do { } while (0)
+#define cpu_hotplug_disable() do { } while (0)
+#endif
+
extern struct bus_type cpu_subsys;
#ifdef CONFIG_HOTPLUG_CPU
--
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