cpu stopping

[Mitsuru IWASAKI]

Hi,

I've created the patches of experimental implementation based on
discussion so far.

http://people.freebsd.org/~iwasaki/acpi/cpustop_hook-20120606.diff

In acpi_wakeup.c, cpususpend_handler() and susppcbs are replaced with
cpustop_handler() and stoppcbs.

This is for RELENG_9 and only for i386 but I think it's enough for the
start.


From: Andriy Gapon <avg at FreeBSD.org>
Subject: Re: cpu stopping
Date: Sun, 03 Jun 2012 22:45:33 +0300
Message-ID: <4FCBBEDD.5000604 at FreeBSD.org>

> > Never mind :) What I'm trying to do in the patches is just to unify
> > amd64/i386 independent part (acpi_wakeup.c) for the code maintenance,
> > so please let's commit it first, then start re-design the
> > cpususpend_handler().
> 
> In no way I am trying to delay your work :)
> Just shared my view on the design of cpu stopping code.

I got it :)

> >> My view of how this should work is:
> >> - there can be only one master CPU that controls all other (slave) CPUs
> >> - the master sets entry and exit hooks
> > 
> > Entry hook for suspending might be
> > ----
> >                 ctx_fpusave(suspfpusave[cpu]);
> >                 wbinvd();
> >                 CPU_SET_ATOMIC(cpu, &stopped_cpus);
> > ----
> > 
> > and for stopping is
> > ----
> >         /* Indicate that we are stopped */
> >         CPU_SET_ATOMIC(cpu, &stopped_cpus);
> > ----
> > 
> > Correct?
> 
> Yes.  The only nit is that CPU_SET_ATOMIC(cpu, &stopped_cpus) could be part of
> the wait loop prologue.  No need to duplicate it in each hook.

OK, I did so.

I hope the patch is not far from your idea.

Thanks!