Re: [Xen-devel] [PATCH 1/6] xen/sched: call cpu_disable_scheduler() via cpu notifier

[Dario Faggioli <dfaggioli@xxxxxxxx>]

On Wed, 2019-03-27 at 17:31 +0100, Juergen Gross wrote:
> On 27/03/2019 17:24, Dario Faggioli wrote:
> > On Mon, 2019-03-18 at 14:11 +0100, Juergen Gross wrote:
> > > cpu_disable_scheduler() is being called from __cpu_disable()
> > > today.
> > > There is no need to call it on the cpu just being disabled, so
> > > use
> > > the CPU_DEAD case of the cpu notifier chain.
> > > 
> > So, what do you mean with "There is no need to call it on the cpu
> > just
> > being disabled"?
> > 
> > Because we still (even after this patch, I mean) call
> > cpu_disable_scheduler() on all non-boot CPUs, aren't we? It's just
> > that
> > right now we call it from __cpu_disable(), with the patch we call
> > it
> > slightly later.
> 
> The CPU_DEAD notifier chain is called on the CPU requesting the other
> one to go down (so on the boot CPU in suspend case). So we call it
> _for_
> all non-boot CPUs in the boot CPU.
> 
Mmm... ok, I see what you mean now.

I guess part of "the problem" is that "call func on cpu A" reads, at
least to me, as both 1) call func so that it acts on and change the
state of cpu A, and 2) call func in such a way that it executes on cpu
A.

But I'm no native speaker, so it may very well be that the confusion is
all and only mine.

Dario
-- 
<<This happens because I choose it to happen!>> (Raistlin Majere)
-----------------------------------------------------------------
Dario Faggioli, Ph.D, http://about.me/dario.faggioli
Software Engineer @ SUSE https://www.suse.com/

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