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

Rusty Russell
2004-11-02T09:41:10Z

On Mon, 2004-11-01 at 13:04 -0500, 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?

get_cpu() both ensures that this CPU won't go down, and ensures we won't
get scheduled off it. It returns the current processor ID, as well.
put_cpu() puts the CPU back.

In my experience it's usually clearer than preempt_disable().

Cheers,
Rusty.
--
A bad analogy is like a leaky screwdriver -- Richard Braakman