From mboxrd@z Thu Jan  1 00:00:00 1970
From: Benjamin Herrenschmidt <benh-XVmvHMARGAS8U2dJNN8I7kB+6BGkLq7r@public.gmane.org>
Subject: Re: [PATCH] sched: provide scheduler_ipi()
 callback in response to smp_send_reschedule()
Date: Wed, 09 Feb 2011 17:14:14 +1100
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To: Peter Zijlstra <peterz-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>
Cc: linux-m32r-ja-rQhvJZKUsGBRYuoOT4C5/9i2O/JbrIOy@public.gmane.org, linux-mips-6z/3iImG2C8G8FEW9MqTrA@public.gmane.org, linux-m32r-rQhvJZKUsGBRYuoOT4C5/9i2O/JbrIOy@public.gmane.org, linux-ia64-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-sh-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Heiko Carstens <heiko.carstens-tA70FqPdS9bQT0dZR+AlfA@public.gmane.org>, Howells <dhowells-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>, Paul Mackerras <paulus-eUNUBHrolfbYtjvyW6yDsg@public.gmane.org>, "H. Peter
	Anvin" <hpa-YMNOUZJC4hwAvxtiuMwx3w@public.gmane.org>, sparclinux-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Linux-Arch <linux-arch-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>, linux-s390-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Jesper Nilsson <jesper.nilsson-VrBV9hrLPhE@public.gmane.org>, Mikael-ZG0+EudsQA8dtHy/vicBwGD2FQJk+8+b@public.gmane.org, Russell King <linux-lFZ/pmaqli7XmaaqVzeoHQ@public.gmane.org>, Takata <takata-TMSiXQfHlQjsTix1lMzHGQ@public.gmane.org>, x86-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org, "James E.J. Bottomley" <jejb-6jwH94ZQLHl74goWV3ctuw@public.gmane.org>, virtualization-qjLDD68F18O7TbgM5vRIOg@public.gmane.org, Ingo Molnar <mingo-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>, xen-devel-GuqFBffKawuULHF6PoxzQEEOCMrvLtNR@public.gmane.org, Chris-ZG0+EudsQA8dtHy/vicBwGD2FQJk+8+b@public.gmane.org, Matt Turner <mattst88-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>, uclinux-dist-devel-ZG0+EudsQA8dtHy/vicBwGD2FQJk+8+b@public.gmane.org, Fen
List-Id: virtualization@lists.linuxfoundation.org

On Mon, 2011-02-07 at 14:54 +0100, Peter Zijlstra wrote:
> On Mon, 2011-02-07 at 10:26 +1100, Benjamin Herrenschmidt wrote:
> > You missed:
> > 
> > diff --git a/arch/powerpc/kernel/smp.c b/arch/powerpc/kernel/smp.c
> > index 9813605..467d122 100644
> > --- a/arch/powerpc/kernel/smp.c
> > +++ b/arch/powerpc/kernel/smp.c
> > @@ -98,6 +98,7 @@ void smp_message_recv(int msg)
> >                 break;
> >         case PPC_MSG_RESCHEDULE:
> >                 /* we notice need_resched on exit */
> > +               scheduler_ipi();
> >                 break;
> >         case PPC_MSG_CALL_FUNC_SINGLE:
> >                 generic_smp_call_function_single_interrupt();
> > 
> > Fold that in and add:
> > 
> > Acked-by: Benjamin Herrenschmidt <benh-XVmvHMARGAS8U2dJNN8I7kB+6BGkLq7r@public.gmane.org>
> 
> Thanks Ben!

BTW. I we lurking at some of our CPU hotplug code and I think I cannot
totally guarantee that this won't be called on an offline CPU. If that's
a problem, you may want to add a test for that.

IE. The call function IPIs are normally not going to be sent to an
offlined CPU, and stop_machine should be a good enough fence here, but
we do abuse reschedule for a number of things (including in some case
to wake up a sleeping CPU that was pseudo-offlined :-)

Cheers,
Ben.