On Wed, 2008-06-04 at 08:28 -0600, Gregory Haskins wrote:
> >> diff --git a/include/linux/sched.h b/include/linux/sched.h
> >> index bb71371..9c5b8c9 100644
> >> --- a/include/linux/sched.h
> >> +++ b/include/linux/sched.h
> >> @@ -970,6 +970,8 @@ struct sched_class {
> >>
> >> void (*join_domain)(struct rq *rq);
> >> void (*leave_domain)(struct rq *rq);
> >> + void (*online)(struct rq *rq);
> >> + void (*offline)(struct rq *rq);
> >
> > Rather unfortunate to add yet another two callbacks, can't this be done
> > with a creative use of leave/join?
>
> Yeah, I was debating how to do this. In fact, as you can see the
> implementation of join/online and leave/offline is identical. I wasnt
> sure if putting a join/leave in the hotplug code made sense, so I
> added a new callback that maps to the same logic. Perhaps what I
> should have done was to s/join/online and s/leave/offline and fixed
> the root-domain code to use the online/offline variant. I like this
> better so I will put out a v2 patch in a few minutes.
>
> I think you are misinterpreting that part. leave/join is fully
> functional and intact. I just merged the two implementations to call
> one function (see the sched_class assignment below)
>
> >
> >> @@ -1278,8 +1284,10 @@ const struct sched_class rt_sched_class = {
> >> .load_balance = load_balance_rt,
> >> .move_one_task = move_one_task_rt,
> >> .set_cpus_allowed = set_cpus_allowed_rt,
> >> - .join_domain = join_domain_rt,
> >> - .leave_domain = leave_domain_rt,
> >> + .join_domain = rq_online_rt,
> >> + .leave_domain = rq_offline_rt,
> >> + .online = rq_online_rt,
> >> + .offline = rq_offline_rt,
> >> .pre_schedule = pre_schedule_rt,
> >> .post_schedule = post_schedule_rt,
> >> .task_wake_up = task_wake_up_rt,
Ah, right - I missed that.
Right - I was just looking to get the cpu-down path to do one ->leave()
extra (aside from leave/join the def_root_domain) so it's basically
unattached - which makes sense for a downed cpu.
Conversely the cpu-up should start with an extra ->join() attaching the
downed cpu again.
I'm thinking doing it that way saves us the extra callbacks. We can do
those if and when the leave/offline behaviour actually divert.
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