Re: [PATCH V3] cpu/hotplug: Cache number of online CPUs

[Mathieu Desnoyers]

----- On Jul 9, 2019, at 10:23 AM, Thomas Gleixner tglx@xxxxxxxxxxxxx wrote:
[...]
> +void set_cpu_online(unsigned int cpu, bool online)
> +{
> +	/*
> +	 * atomic_inc/dec() is required to handle the horrid abuse of this
> +	 * function by the reboot and kexec code which invokes it from

invokes -> invoke

> +	 * IPI/NMI broadcasts when shutting down CPUs. Inocation from

Inocation -> Invocation

The rest looks good!

Reviewed-by: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx>

> +	 * regular CPU hotplug is properly serialized.
> +	 *
> +	 * Note, that the fact that __num_online_cpus is of type atomic_t
> +	 * does not protect readers which are not serialized against
> +	 * concurrent hotplug operations.
> +	 */
> +	if (online) {
> +		if (!cpumask_test_and_set_cpu(cpu, &__cpu_online_mask))
> +			atomic_inc(&__num_online_cpus);
> +	} else {
> +		if (cpumask_test_and_clear_cpu(cpu, &__cpu_online_mask))
> +			atomic_dec(&__num_online_cpus);
> +	}
> +}
> +
> /*
>  * Activate the first processor.
>   */

-- 
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com