Re: + i386-time-avoid-pit-smp-lockups.patch added to -mm tree

[Nick Piggin]

Daniel Walker wrote:
> On Thu, 2006-10-19 at 15:47 +0200, Andi Kleen wrote:
>
> > On Thursday 19 October 2006 15:44, Daniel Walker wrote:
> >
> > > On Wed, 2006-10-11 at 14:26 -0700, akpm@xxxxxxxx wrote:
> > >
> > >
> > > > diff -puN arch/i386/kernel/i8253.c~i386-time-avoid-pit-smp-lockups arch/i386/kernel/i8253.c
> > > > --- a/arch/i386/kernel/i8253.c~i386-time-avoid-pit-smp-lockups
> > > > +++ a/arch/i386/kernel/i8253.c
> > > > @@ -109,7 +109,7 @@ static struct clocksource clocksource_pi
> > > >
> > > > static int __init init_pit_clocksource(void)
> > > > {
> > > > -	if (num_possible_cpus() > 4) /* PIT does not scale! */
> > > > +	if (num_possible_cpus() > 1) /* PIT does not scale! */
> > > > 		return 0;
> > >
> > > Can we ifdef some code here on CONFIG_SMP . It bugs me that there just
> > > dead code laying around on smp systems.
> >
> > The optimizer should optimize it all out since num_possible_cpus() is a 0
> > constant on UP.
>
>
> You just mean the if statement above though? I was talking more about
> the structure above this called "clocksource_pit" which isn't used on
> SMP systems due to this code addition. AFAIK init_pit_clocksource()
> could disappear along with the clocksource structure ..

An SMP kernel can boot on UP hardware, in which case I think
num_possible_cpus() will be 1, won't it?

--
SUSE Labs, Novell Inc.
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