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SubjectRe: [PATCH] Force rcutorture tasks to spread over CPUs
On Wed, Jun 27, 2007 at 08:30:55AM +0200, Ingo Molnar wrote:
>
> * Andrew Morton <akpm@linux-foundation.org> wrote:
>
> > On Tue, 12 Jun 2007 21:28:04 -0700
> > "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> wrote:
> >
> > > + while (!startwriters)
> > > + barrier(); /* Force scheduler to spread over CPUs. */
> >
> > one wonders whether a cpu_relax() would be a bit nicer here. That
> > implicitly does a barrier().
> >
> > This patch doesn't make much sense for non-SMP builds?
>
> i think this patch should be unnecessary because we found the real SMP
> balancing bug in the upstream scheduler causing this rcu problem, see:
>
> commit 92c4ca5c3a5e180e9762438db235f41d192cb955
> Author: Christoph Lameter <clameter@sgi.com>
> Date: Sat Jun 23 17:16:33 2007 -0700
>
> sched: fix next_interval determination in idle_balance()

Ingo is correct -- applying the above patch caused the scheduler to
correctly balance the rcutorture tasks, so that my patch to rcutorture
is no longer needed. Which is a very good thing! ;-)

Thanx, Paul
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