Date: Wed, 31 Oct 2012 13:08:42 -0700
From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
To: Christoph Lameter <cl@linux.com>
Cc: Shan Wei <shanwei88@gmail.com>, dipankar@in.ibm.com,
        Kernel-Maillist <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 7/9] rcu:  use this_cpu_ptr per-cpu helper instead of
 per_cpu_ptr(p, raw_smp_processor_id())
Message-ID: <20121031200842.GC3027@linux.vnet.ibm.com>
Reply-To: paulmck@linux.vnet.ibm.com
References: <50910A17.1090600@gmail.com>
 <0000013ab7eefc03-20a4ba94-f83f-4624-9dac-dfe3924277b4-000000@email.amazonses.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <0000013ab7eefc03-20a4ba94-f83f-4624-9dac-dfe3924277b4-000000@email.amazonses.com>
User-Agent: Mutt/1.5.21 (2010-09-15)
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 1167
Lines: 35

On Wed, Oct 31, 2012 at 05:47:04PM +0000, Christoph Lameter wrote:
> On Wed, 31 Oct 2012, Shan Wei wrote:
> 
> > Signed-off-by: Shan Wei <davidshan@tencent.com>
> > ---
> >  kernel/rcutree.c |    2 +-
> >  1 files changed, 1 insertions(+), 1 deletions(-)
> >
> > diff --git a/kernel/rcutree.c b/kernel/rcutree.c
> > index 74df86b..3a21fcf 100644
> > --- a/kernel/rcutree.c
> > +++ b/kernel/rcutree.c
> > @@ -1960,7 +1960,7 @@ static void force_quiescent_state(struct rcu_state *rsp)
> >  	struct rcu_node *rnp_old = NULL;
> >
> >  	/* Funnel through hierarchy to reduce memory contention. */
> > -	rnp = per_cpu_ptr(rsp->rda, raw_smp_processor_id())->mynode;
> > +	rnp = this_cpu_ptr(rsp->rda)->mynode;
> 
> Do
> 
> 	rnp = this_cpu_read(rsp->rda->mynode);
> 
> instad.

One thing to keep in mind -- the only purpose of this is to diffuse
memory contention.  So there is no need to disable preemption.

							Thanx, Paul

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