[PATCH RESEND v4] reboot: support offline CPUs before reboot

Rob Landley rob at landley.net
Thu Jan 16 20:20:28 PST 2020

On 1/14/20 5:06 AM, Hsin-Yi Wang wrote:
> This patch adds a config ARCH_OFFLINE_CPUS_ON_REBOOT, which would offline cpus in
> migrate_to_reboot_cpu(). If non reboot cpus are all offlined here, the loop for
> checking online cpus would be an empty loop. If architecture don't enable this
> config, or some cpus somehow fails to offline, it would fallback to ipi
> function.

I'm curious:

> +# Select to do a full offline on secondary CPUs before reboot.
> +	bool "Support for offline CPUs before reboot"
> +	depends on HOTPLUG_CPU

The new symbol can't be selected without the other symbol.


And the other symbol automatically selects the new one.

Why are you adding a second symbol that means the same thing as the existing symbol?

> +extern int freeze_secondary_cpus(int primary, bool reboot);
> +#endif

Couldn't that just test HOTPLUG_CPU? What's the second symbol for? (You can have
empty stub functions when architectures don't support a thing...)


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