Re: CPU Hotplug rework

From: Peter Zijlstra
Date: Mon Mar 26 2012 - 04:02:21 EST

On Mon, 2012-03-26 at 11:11 +1030, Rusty Russell wrote:
> Obviously, having callbacks hanging around until the CPU comes back is
> not viable, nor is blocking preempt during the callbacks. Calling
> get_online_cpus() is too heavy.

-rt has patches (albeit somewhat ugly) to make get_online_cpus() a br
style rw-lock. That is, it makes the read side a per-cpu lock/counter so
that its much faster and only touches cpu-local state in the common

It would be good to clean those up and make get_online_cpus() fast and
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