Re: [PATCH] [CPU-HOTPLUG] convert cpucontrol to be a rwsem

Zwane Mwaikambo
2004-11-02T00:17:35Z

On Mon, 1 Nov 2004, Lee Revell wrote:

> On Mon, 2004-11-01 at 07:00 -0700, Zwane Mwaikambo wrote:
> > Agreed it makes a lot more sense, i think there could be some places where
> > we use preempt_disable to protect against cpu offline which could
> > converted, but that can come later.
> >
>
> You know I picked up Robert Love's book the other day and was surprised
> to read we are not supposed to be using preempt_disable, there is a
> per_cpu interface for exactly this kind of thing. Which is currently
> recommended?

It's on a case by case basis, preempt_disable has the side effect of
ensuring that you run through that specific critical section without being
interrupted by scheduling, this happens to also block out various things
like RCU and the stop_machine (used by cpu hotplug) code amongst others.
I'm curious what is the excert that you're referring to?

Thanks,
Zwane