(2012/07/20 17:01), Michal Hocko wrote:

On Fri 20-07-12 10:20:29, KAMEZAWA Hiroyuki wrote:
[...]

quoted

Hmm, can't cgroup_lock() be implemented as


void cgroup_lock()
{
	get_online_cpus()
	lock_memory_hotplug()
	mutex_lock(&cgroup_mutex);
}

This is really ugly and it wouldn't help much anyway. Notifier which
takes the cgroup_lock is called when cpu_hotplug.lock is held already.

Hm ? IIUC, notifer will not work until put_online_cpu() is called.

You would need to call cgroup_lock() before taking the cpu_hotplug.lock
and remove it from notifiers. I think this should be doable but I didn't
have too much time to look deeper into it.

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