From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752049Ab1K2A0I (ORCPT ); Mon, 28 Nov 2011 19:26:08 -0500 Received: from mail-ey0-f174.google.com ([209.85.215.174]:49261 "EHLO mail-ey0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750900Ab1K2A0G (ORCPT ); Mon, 28 Nov 2011 19:26:06 -0500 Date: Tue, 29 Nov 2011 01:26:01 +0100 From: Frederic Weisbecker To: "Paul E. McKenney" Cc: LKML , Josh Triplett Subject: Re: [PATCH 1/4] rcu: Don't check irq nesting from rcu idle entry/exit Message-ID: <20111129002558.GA18182@somewhere.redhat.com> References: <1322515487-18690-1-git-send-email-fweisbec@gmail.com> <1322515487-18690-2-git-send-email-fweisbec@gmail.com> <20111129002244.GO2346@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20111129002244.GO2346@linux.vnet.ibm.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Nov 28, 2011 at 04:22:44PM -0800, Paul E. McKenney wrote: > On Mon, Nov 28, 2011 at 10:24:44PM +0100, Frederic Weisbecker wrote: > > rcu_idle_enter() and rcu_idle_exit() don't need to check > > the irq nesting as they are not called from irq. > > > > Only check dyntick_nesting from rcu_irq_enter() and > > rcu_irq_exit(). > > > > Signed-off-by: Frederic Weisbecker > > Cc: Josh Triplett > > --- > > kernel/rcutree.c | 18 ++++++++---------- > > 1 files changed, 8 insertions(+), 10 deletions(-) > > I have queued this. I had to update it to deal with a recent conflicting > update, please see below for the new version. > > Thanx, Paul Hmm, seems there is a problem. Look below: > > ------------------------------------------------------------------------ > > rcu: Don't check irq nesting from rcu idle entry/exit > > Because tasks do not nest, rcu_idle_enter() and rcu_idle_exit() do > not need to check for nesting. This commit therefore moves nesting > checks from rcu_idle_enter_common() to rcu_irq_exit() and from > rcu_idle_exit_common() to rcu_irq_enter(). > > Signed-off-by: Frederic Weisbecker > Cc: Josh Triplett > Signed-off-by: Paul E. McKenney > > diff --git a/kernel/rcutree.c b/kernel/rcutree.c > index bf085d7..54d9b4f 100644 > --- a/kernel/rcutree.c > +++ b/kernel/rcutree.c > @@ -350,10 +350,6 @@ static int rcu_implicit_offline_qs(struct rcu_data *rdp) > */ > static void rcu_idle_enter_common(struct rcu_dynticks *rdtp, long long oldval) > { > - if (rdtp->dynticks_nesting) { > - trace_rcu_dyntick("--=", oldval, rdtp->dynticks_nesting); > - return; > - } > trace_rcu_dyntick("Start", oldval, rdtp->dynticks_nesting); > if (!is_idle_task(current)) { > struct task_struct *idle = idle_task(smp_processor_id()); > @@ -426,7 +422,10 @@ void rcu_irq_exit(void) > oldval = rdtp->dynticks_nesting; > rdtp->dynticks_nesting--; > WARN_ON_ONCE(rdtp->dynticks_nesting < 0); > - rcu_idle_enter_common(rdtp, oldval); > + if (rdtp->dynticks_nesting) > + trace_rcu_dyntick("--=", oldval, rdtp->dynticks_nesting); > + else > + rcu_idle_enter_common(rdtp, oldval); > local_irq_restore(flags); > } > > @@ -439,10 +438,6 @@ void rcu_irq_exit(void) > */ > static void rcu_idle_exit_common(struct rcu_dynticks *rdtp, long long oldval) > { > - if (oldval) { > - trace_rcu_dyntick("++=", oldval, rdtp->dynticks_nesting); > - return; > - } > smp_mb__before_atomic_inc(); /* Force ordering w/previous sojourn. */ > atomic_inc(&rdtp->dynticks); > /* CPUs seeing atomic_inc() must see later RCU read-side crit sects */ > @@ -519,6 +514,10 @@ void rcu_irq_enter(void) > rdtp->dynticks_nesting++; > WARN_ON_ONCE(rdtp->dynticks_nesting == 0); > rcu_idle_exit_common(rdtp, oldval); It's now calling rcu_idle_exit_common twice? > + if (oldval) > + trace_rcu_dyntick("++=", oldval, rdtp->dynticks_nesting); > + else > + rcu_idle_exit_common(rdtp, oldval); > local_irq_restore(flags); > } > >