Re: [patch 2/2] sched: dynticks idle load balancing - v2

From: Nick Piggin
Date: Wed Feb 21 2007 - 22:14:32 EST


On Wed, Feb 21, 2007 at 12:23:44PM -0800, Andrew Morton wrote:
> On Fri, 16 Feb 2007 18:08:42 -0800

> > +int select_nohz_load_balancer(int stop_tick)
> > +{
> > + int cpu = smp_processor_id();
> > +
> > + if (stop_tick) {
> > + cpu_set(cpu, nohz.cpu_mask);
> > + cpu_rq(cpu)->in_nohz_recently = 1;
> > +
> > + /*
> > + * If we are going offline and still the leader, give up!
> > + */
> > + if (cpu_is_offline(cpu) && nohz.load_balancer == cpu) {
> > + if (cmpxchg(&nohz.load_balancer, cpu, -1) != cpu)
>
> So we require that architectures which implement CONFIG_NO_HZ also
> implement cmpxchg.

Just use atomic_cmpxchg, please.
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