From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758994Ab2FPBB6 (ORCPT ); Fri, 15 Jun 2012 21:01:58 -0400 Received: from e38.co.us.ibm.com ([32.97.110.159]:53893 "EHLO e38.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758948Ab2FPBB5 (ORCPT ); Fri, 15 Jun 2012 21:01:57 -0400 Date: Fri, 15 Jun 2012 18:01:49 -0700 From: "Paul E. McKenney" To: Josh Triplett 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, niv@us.ibm.com, tglx@linutronix.de, peterz@infradead.org, rostedt@goodmis.org, Valdis.Kletnieks@vt.edu, dhowells@redhat.com, eric.dumazet@gmail.com, darren@dvhart.com, fweisbec@gmail.com, patches@linaro.org Subject: Re: [PATCH tip/core/rcu 13/15] rcu: Introduce for_each_rcu_flavor() and use it Message-ID: <20120616010149.GW2389@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <20120615210550.GA27506@linux.vnet.ibm.com> <1339794370-28119-1-git-send-email-paulmck@linux.vnet.ibm.com> <1339794370-28119-13-git-send-email-paulmck@linux.vnet.ibm.com> <20120615235239.GE7613@leaf> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20120615235239.GE7613@leaf> User-Agent: Mutt/1.5.21 (2010-09-15) X-Content-Scanned: Fidelis XPS MAILER x-cbid: 12061601-5518-0000-0000-00000535DB4D Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jun 15, 2012 at 04:52:40PM -0700, Josh Triplett wrote: > On Fri, Jun 15, 2012 at 02:06:08PM -0700, Paul E. McKenney wrote: > > From: "Paul E. McKenney" > > > > The arrival of TREE_PREEMPT_RCU some years back included some ugly > > code involving either #ifdef or #ifdef'ed wrapper functions to iterate > > over all non-SRCU flavors of RCU. This commit therefore introduces > > a for_each_rcu_flavor() iterator over the rcu_state structures for each > > flavor of RCU to clean up a bit of the ugliness. > > > > Signed-off-by: Paul E. McKenney > > Great cleanup! > > A few comments below, though. > > > kernel/rcutree.c | 53 +++++++++++++--------- > > kernel/rcutree.h | 12 ++--- > > kernel/rcutree_plugin.h | 116 ----------------------------------------------- > > 3 files changed, 36 insertions(+), 145 deletions(-) > > Awesome diffstat. ;-) > > diff --git a/kernel/rcutree.c b/kernel/rcutree.c > > index bd4e41c..75ad92a 100644 > > --- a/kernel/rcutree.c > > +++ b/kernel/rcutree.c > > @@ -84,6 +84,7 @@ struct rcu_state rcu_bh_state = RCU_STATE_INITIALIZER(rcu_bh, call_rcu_bh); > > DEFINE_PER_CPU(struct rcu_data, rcu_bh_data); > > > > static struct rcu_state *rcu_state; > > +LIST_HEAD(rcu_struct_flavors); > > Does any means exist to turn this into a constant array known at compile > time rather than a runtime linked list? Having this as a compile-time > constant may allow the compiler to unroll for_each_rcu_flavor and > potentially inline the calls inside it. I could do that, but none of the traversals is anywhere near performance critical, and all the ways I can think of to do this are uglier than the list. > > @@ -2539,9 +2548,10 @@ rcu_init_percpu_data(int cpu, struct rcu_state *rsp, int preemptible) > > > > static void __cpuinit rcu_prepare_cpu(int cpu) > > { > > - rcu_init_percpu_data(cpu, &rcu_sched_state, 0); > > - rcu_init_percpu_data(cpu, &rcu_bh_state, 0); > > - rcu_preempt_init_percpu_data(cpu); > > + struct rcu_state *rsp; > > + > > + for_each_rcu_flavor(rsp) > > + rcu_init_percpu_data(cpu, rsp, 0); > > This results in passing 0 as the "preemptible" parameter of > rcu_init_percpu_data, which seems wrong if the preemptible parameter has > any meaning at all. :) Good catch! Hmmm... Probably best to move this to the rcu_state initialization. > > @@ -2577,18 +2588,15 @@ static int __cpuinit rcu_cpu_notify(struct notifier_block *self, > > * touch any data without introducing corruption. We send the > > * dying CPU's callbacks to an arbitrarily chosen online CPU. > > */ > > - rcu_cleanup_dying_cpu(&rcu_bh_state); > > - rcu_cleanup_dying_cpu(&rcu_sched_state); > > - rcu_preempt_cleanup_dying_cpu(); > > - rcu_cleanup_after_idle(cpu); > > + for_each_rcu_flavor(rsp) > > + rcu_cleanup_dying_cpu(rsp); > > Why did rcu_cleanup_after_idle go away here? Because I fat-fingered it. Thank you very much for spotting this. It would have been nasty to find otherwise. Thanx, Paul