From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752613Ab1GTClU (ORCPT ); Tue, 19 Jul 2011 22:41:20 -0400 Received: from casper.infradead.org ([85.118.1.10]:39796 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752456Ab1GTClT convert rfc822-to-8bit (ORCPT ); Tue, 19 Jul 2011 22:41:19 -0400 Subject: Re: [PATCH tip/core/urgent 1/7] rcu: decrease rcu_report_exp_rnp coupling with scheduler From: Peter Zijlstra To: "Paul E. McKenney" Cc: linux-kernel@vger.kernel.org, mingo@elte.hu, laijs@cn.fujitsu.com, dipankar@in.ibm.com, akpm@linux-foundation.org, mathieu.desnoyers@polymtl.ca, josh@joshtriplett.org, niv@us.ibm.com, tglx@linutronix.de, rostedt@goodmis.org, Valdis.Kletnieks@vt.edu, dhowells@redhat.com, eric.dumazet@gmail.com, darren@dvhart.com, patches@linaro.org, greearb@candelatech.com, edt@aei.ca In-Reply-To: <1311121103-16978-1-git-send-email-paulmck@linux.vnet.ibm.com> References: <20110720001738.GA16369@linux.vnet.ibm.com> <1311121103-16978-1-git-send-email-paulmck@linux.vnet.ibm.com> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8BIT Date: Wed, 20 Jul 2011 04:40:18 +0200 Message-ID: <1311129618.5345.2.camel@twins> Mime-Version: 1.0 X-Mailer: Evolution 2.30.3 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 2011-07-19 at 17:18 -0700, Paul E. McKenney wrote: > +++ b/kernel/rcutree_plugin.h > @@ -696,8 +696,10 @@ static void rcu_report_exp_rnp(struct rcu_state *rsp, struct rcu_node *rnp) > raw_spin_lock_irqsave(&rnp->lock, flags); > for (;;) { > if (!sync_rcu_preempt_exp_done(rnp)) > + raw_spin_unlock_irqrestore(&rnp->lock, flags); > break; I bet that'll all work much better if you wrap it in curly braces like: if (!sync_rcu_preempt_exp_done(rnp)) { raw_spin_unlock_irqrestore(&rnp->lock, flags); break; } That might also explain those explosions Ed and Ben have been seeing. > if (rnp->parent == NULL) { > + raw_spin_unlock_irqrestore(&rnp->lock, flags); > wake_up(&sync_rcu_preempt_exp_wq); > break; > } > @@ -707,7 +709,6 @@ static void rcu_report_exp_rnp(struct rcu_state *rsp, struct rcu_node *rnp) > raw_spin_lock(&rnp->lock); /* irqs already disabled */ > rnp->expmask &= ~mask; > } > - raw_spin_unlock_irqrestore(&rnp->lock, flags); > }