linux-kernel - Re: [PATCH] Force rcutorture tasks to spread over CPUs

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Message-ID: <20070627063055.GB3186@elte.hu>
Date:	Wed, 27 Jun 2007 08:30:55 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	paulmck@...ux.vnet.ibm.com, linux-kernel@...r.kernel.org,
	josh@...edesktop.org, dipankar@...ibm.com
Subject: Re: [PATCH] Force rcutorture tasks to spread over CPUs


* Andrew Morton <akpm@...ux-foundation.org> wrote:

> On Tue, 12 Jun 2007 21:28:04 -0700
> "Paul E. McKenney" <paulmck@...ux.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@....com>
 Date:   Sat Jun 23 17:16:33 2007 -0700

     sched: fix next_interval determination in idle_balance()

	Ingo
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