Re: [RFC PATCH v2 02/10] CPU hotplug: Provide APIs for "full" atomicreaders to prevent CPU offline

From: Tejun Heo
Date: Wed Dec 05 2012 - 15:57:41 EST


On Thu, Dec 06, 2012 at 02:01:35AM +0530, Srivatsa S. Bhat wrote:
> Yes, that _sounds_ sufficient, but IMHO it won't be, in practice. The
> *number* of call-sites that you need to convert from preempt_disable/enable
> to get/put_online_cpus_atomic() won't be too many, however the *frequency*
> of usage of those call-sites can potentially be very high.

I don't think that will be the case and, even if it is, doing it this
way would make it difficult to tell. The right thing to do is
replacing stop_machine with finer grained percpu locking first.
Refining it further should happen iff that isn't enough and there
isn't an simpler solution. So, let's please do the simple conversion


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