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[Xen-devel] Re: [PATCH] sched: provide scheduler_ipi() callback in response to smp_send_reschedule()
- To: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx>
- From: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
- Date: Wed, 09 Feb 2011 10:37:24 +0100
- Cc: linux-m32r-ja@xxxxxxxxxxxxxxxxx, linux-mips@xxxxxxxxxxxxxx, linux-m32r@xxxxxxxxxxxxxxxxx, linux-ia64@xxxxxxxxxxxxxxx, linux-sh@xxxxxxxxxxxxxxx, Heiko Carstens <heiko.carstens@xxxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxx, Howells <dhowells@xxxxxxxxxx>, Paul Mackerras <paulus@xxxxxxxxx>, "H. Peter Anvin" <hpa@xxxxxxxxx>, sparclinux@xxxxxxxxxxxxxxx, Linux-Arch <linux-arch@xxxxxxxxxxxxxxx>, linux-s390@xxxxxxxxxxxxxxx, Jesper Nilsson <jesper.nilsson@xxxxxxxx>, Mikael, Russell King <linux@xxxxxxxxxxxxxxxx>, Takata <takata@xxxxxxxxxxxxxx>, x86@xxxxxxxxxx, "James E.J. Bottomley" <jejb@xxxxxxxxxxxxxxxx>, virtualization@xxxxxxxxxxxxxx, Ingo Molnar <mingo@xxxxxxxxxx>, Chris, Matt Turner <mattst88@xxxxxxxxx>, uclinux-dist-devel@xxxxxxxxxxxxxxxxxxxx, Fenghua Yu <fenghua.yu@xxxxxxxxx>, Mike Frysinger <vapier@xxxxxxxxxx>, user-mode-linux-devel@xxxxxxxxxxxxxxxxxxxxx, Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>, Jeff Dike <jdike@xxxxxxxxxxx>, Metcalf <cmetcalf@xxxxxxxxxx>, David, Starvik <starvik@xxxxxxxx>, Schwidefsky <schwidefsky@xxxxxxxxxx>, Jeremy Fitzhardinge <jeremy.fitzhardinge@xxxxxxxxxx>, Ivan Kokshaysky <ink@xxxxxxxxxxxxxxxxxxxx>, user-mode-linux-user@xxxxxxxxxxxxxxxxxxxxx, Martin, Gleixner <tglx@xxxxxxxxxxxxx>, linux-arm-kernel@xxxxxxxxxxxxxxxxxxx, Richard Henderson <rth@xxxxxxxxxxx>, Thomas, Luck <tony.luck@xxxxxxxxx>, linux-parisc@xxxxxxxxxxxxxxx, linux-cris-kernel@xxxxxxxx, Hirokazu, linux-am33-list@xxxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx, Ralf Baechle <ralf@xxxxxxxxxxxxxx>, "David S. Miller" <davem@xxxxxxxxxxxxx>, Kyle McMartin <kyle@xxxxxxxxxxx>, Paul Mundt <lethal@xxxxxxxxxxxx>, linux-alpha@xxxxxxxxxxxxxxx, Tony, linux390@xxxxxxxxxx, Koichi Yasutake <yasutake.koichi@xxxxxxxxxxxxxxxx>, linuxppc-dev@xxxxxxxxxxxxxxxx, Helge Deller <deller@xxxxxx>
- Delivery-date: Wed, 09 Feb 2011 05:33:06 -0800
- List-id: Xen developer discussion <xen-devel.lists.xensource.com>
On Wed, 2011-02-09 at 17:14 +1100, Benjamin Herrenschmidt wrote:
> 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@xxxxxxxxxxxxxxxxxxx>
> >
> > 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 :-)
Hmm, I _think_ that should all work out nicely, but we'll see, if when
this stuff hits the tree powerpc machines start falling over we'd better
put that check in ;-)
Meanwhile I'm going to preserve this comment in the changelog of this
patch so we don't forget.
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