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

[Daniel Walker]

On Thu, 2006-10-19 at 16:50 +0200, Andi Kleen wrote:
> On Thursday 19 October 2006 16:48, Nick Piggin wrote:
> > Andi Kleen wrote:
> > >>An SMP kernel can boot on UP hardware, in which case I think
> > >>num_possible_cpus() will be 1, won't it?
> > > 
> > > 
> > > 0 was a typo, i meant 1 for UP of course. 0 would be nonsensical.
> > 
> > Sure, I realised that. For a UP kernel, the test will compile away.
> > 
> > But Daniel seems to say there is dead code that could be compiled
> > out for SMP kernels. I just don't think that is possible because the
> > SMP kernel can boot a UP system where num_possible_cpus() is 1.
> 
> I thought he meant !CONFIG_SMP kernels.

definitely CONFIG_SMP=y . The code block I quoted would disable the PIT
clocksource w/ more than one cpu. So the pit clocksource is just dead
weight on SMP systems. However, like Nick was saying it's possible to
boot CONFIG_SMP on a UP system, but removing the pit in that situation
may not hurt anything.

Daniel 

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/