Re: [RFC][PATCH 12/13] stop_machine: Remove lglock

[Oleg Nesterov]

On 06/23, Oleg Nesterov wrote:
>
>
> It would be nice to remove stop_cpus_mutex, it actually protects
> stop_cpus_work... Then probably stop_two_cpus() can just use
> stop_cpus(). We could simply make stop_cpus_mutex per-cpu too,
> but this doesn't look nice.

IOW. Suppose we add ->work_mutex into struct cpu_stopper. Btw,
I think we should move all per-cpu variables there...

Now,

	lock_stop_cpus_works(cpumask)
	{
		for_each_cpu(cpu, cpumask)
			mutex_lock(per_cpu(cpu_stopper_task, cpu).work_mutex);
	}

	unlock_stop_cpus_works(cpumask)
	{
		for_each_cpu(cpu, cpumask)
			mutex_lock(...);
	}

which should be used instead of stop_cpus_mutex. After this change
stop_two_cpus() can just use stop_cpus().


Off-topic. Can't we make __stop_machine() static? The only caller,
_cpu_down() can safely call stop_machine(), get_online_cpus() is
fine under cpu_hotplug_begin().

Oleg.

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