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

From: Srivatsa S. Bhat
Date: Wed Dec 05 2012 - 23:32:50 EST

On 12/06/2012 02:27 AM, Tejun Heo wrote:
> Hello,
> 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
> first.

Hmm, OK, that sounds like a good plan. So I'll drop the "light" and
"full" variants for now and work on providing a straight-forward
get/put_online_cpus_atomic() APIs.

Thank you!

Srivatsa S. Bhat

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