On Mon, 21 May 2012 10:25:21 +0200 (CEST), Thomas Gleixner [off-list ref] wrote:

On Mon, 21 May 2012, Rusty Russell wrote:

quoted

On Fri, 20 Apr 2012 16:18:04 +0200 (CEST), Thomas Gleixner [off-list ref] wrote:

quoted

On Fri, 20 Apr 2012, Srivatsa S. Bhat wrote:
The whole notifier business needs a redesign as well, because we don't
have a way to express proper dependencies, we add random notifier
points and the teardown path is ass backwards. The whole thing wants
to be a tree which can be walked in either direction and from any
point. Right now we cut the trunk first and keep the single limb up
with a helicopter and start dismantling it.

But there are two ways to do it.  One is to eliminate the need for
callbacks.  The other is to make a full dependency-based callback

What do you mean with fully eliminating the need for callbacks. Do you
want to put the necessary bringup/shutdown function calls just in the
core code so we get rid of the notifiers or do you have something
different in mind ?

Eliminate is probably too hard, but with park/unpark I can see it
getting less common.  Maybe few enough that we can simplify.

quoted

Not sure whether calling notifiers in parallel is going to be a big win:
they'll end up fighting over the cpu we're taking down.  But I could be
wrong.

I'm not going to aim for parallel in the first place. That was just an
idea and if we chose the right implementation then parallelism can be
added later.

Parallel CPUs going offline/online is probably a bigger win.  Both for
suspend/resume and powersaving.

quoted

The original concept of stopping the machine for cpu hotplug and trying
not to effect any other kernel code has jumped the shark: I think we
need to look seriously at a complete rewrite where we don't use
stop_machine.

Yep. Working on it. :)

I thought you might be :)

I'd love to review once you've got something.

Cheers,
Rusty.