[PATCHv4 4/6] arm64: add CPU_HOTPLUG infrastructure

[mark.rutland@arm.com (Mark Rutland)]

On Fri, Oct 11, 2013 at 11:24:28PM +0100, Stephen Boyd wrote:
> On 10/11/13 11:24, Mark Rutland wrote:
> > diff --git a/arch/arm64/include/asm/cpu_ops.h b/arch/arm64/include/asm/cpu_ops.h
> > index 1720be6..f4a11a3 100644
> > --- a/arch/arm64/include/asm/cpu_ops.h
> > +++ b/arch/arm64/include/asm/cpu_ops.h
> > @@ -34,6 +34,11 @@ struct device_node;
> >   * @cpu_boot:	Boots a cpu into the kernel.
> >   * @cpu_postboot: Optionally, perform any post-boot cleanup or necesary
> >   *		synchronisation. Called from the cpu being booted.
> > + * @cpu_disable: Prepares a cpu to die. May fail for some mechanism-specific
> > + * 		reason, which will cause the hot unplug to be aborted. Called
> > + * 		from the cpu to be killed.
> > + * @cpu_die:	Makes the a leave the kernel. Must not fail. Called from the
> 
> Makes the cpu? Makes a cpu?

Whoops. I've fixed this to "Makes a cpu".

> 
> > + *		cpu being killed.
> >   */
> >  struct cpu_operations {
> >  	const char	*name;
> > @@ -41,6 +46,10 @@ struct cpu_operations {
> >  	int		(*cpu_prepare)(unsigned int);
> >  	int		(*cpu_boot)(unsigned int);
> >  	void		(*cpu_postboot)(void);
> > +#ifdef CONFIG_HOTPLUG_CPU
> > +	int		(*cpu_disable)(unsigned int cpu);
> > +	void		(*cpu_die)(unsigned int cpu);
> > +#endif
> >  };
> >  
> >  extern const struct cpu_operations *cpu_ops[NR_CPUS];
> > diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c
> > index 6806bc4..888776e 100644
> > --- a/arch/arm64/kernel/smp.c
> > +++ b/arch/arm64/kernel/smp.c
> [snip]
> > +
> > +/*
> > + * Called from the idle thread for the CPU which has been shutdown.
> > + *
> > + * Note that we disable IRQs here, but do not re-enable them
> > + * before returning to the caller. This is also the behaviour
> > + * of the other hotplug-cpu capable cores, so presumably coming
> > + * out of idle fixes this.
> > + */
> > +void __ref cpu_die(void)
> 
> __ref is unnecessary now that __cpuinit is gone. I see arm32 needs the
> same treatment.

Good point. Removed.

> 
> > +{
> > +	unsigned int cpu = smp_processor_id();
> > +
> > +	idle_task_exit();
> > +
> > +	local_irq_disable();
> > +	mb();
> 
> Can you please comment this mb().

It looks like the mb is a holdover from an earlier version, and is
superfluous. Removed.

Cheers,
Mark.