From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752390AbaBQVvH (ORCPT ); Mon, 17 Feb 2014 16:51:07 -0500 Received: from relay5-d.mail.gandi.net ([217.70.183.197]:35421 "EHLO relay5-d.mail.gandi.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750939AbaBQVvF (ORCPT ); Mon, 17 Feb 2014 16:51:05 -0500 X-Originating-IP: 50.43.14.201 Date: Mon, 17 Feb 2014 13:50:53 -0800 From: Josh Triplett To: "Paul E. McKenney" Cc: linux-kernel@vger.kernel.org, mingo@kernel.org, laijs@cn.fujitsu.com, dipankar@in.ibm.com, akpm@linux-foundation.org, mathieu.desnoyers@efficios.com, niv@us.ibm.com, tglx@linutronix.de, peterz@infradead.org, rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com, darren@dvhart.com, fweisbec@gmail.com, oleg@redhat.com, sbw@mit.edu Subject: Re: [PATCH tip/core/rcu 1/3] rcu: Optimize rcu_is_nocb_cpu() for RCU_NOCB_CPU_ALL Message-ID: <20140217215053.GE7941@thin> References: <20140217214007.GA6609@linux.vnet.ibm.com> <1392673227-7066-1-git-send-email-paulmck@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1392673227-7066-1-git-send-email-paulmck@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, Feb 17, 2014 at 01:40:25PM -0800, Paul E. McKenney wrote: > From: "Paul E. McKenney" > > If CONFIG_RCU_NOCB_CPU_ALL=y, then rcu_is_nocb_cpu() will always > return true, however, the current version nevertheless checks > rcu_nocb_mask. This commit therefore creates a static inline > implementation of rcu_is_nocb_cpu() that unconditionally returns > true when CONFIG_RCU_NOCB_CPU_ALL=y. > > Signed-off-by: Paul E. McKenney One suggestion below. With or without that change: Reviewed-by: Josh Triplett > include/linux/rcupdate.h | 4 ++++ > kernel/rcu/tree_plugin.h | 2 ++ > 2 files changed, 6 insertions(+) > > diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h > index 72bf3a01a4ee..92365b1fede4 100644 > --- a/include/linux/rcupdate.h > +++ b/include/linux/rcupdate.h > @@ -1016,7 +1016,11 @@ static inline notrace void rcu_read_unlock_sched_notrace(void) > __kfree_rcu(&((ptr)->rcu_head), offsetof(typeof(*(ptr)), rcu_head)) > > #ifdef CONFIG_RCU_NOCB_CPU > +#ifdef CONFIG_RCU_NOCB_CPU_ALL > +static inline bool rcu_is_nocb_cpu(int cpu) { return true; } > +#else /* #ifdef CONFIG_RCU_NOCB_CPU_ALL */ > bool rcu_is_nocb_cpu(int cpu); > +#endif /* #else #ifdef CONFIG_RCU_NOCB_CPU_ALL */ > #else > static inline bool rcu_is_nocb_cpu(int cpu) { return false; } > #endif /* #else #ifdef CONFIG_RCU_NOCB_CPU */ This seem clearer if written without the nesting: #if defined(CONFIG_RCU_NOCB_CPU_ALL) static inline bool rcu_is_nocb_cpu(int cpu) { return true; } #elif defined(CONFIG_RCU_NOCB_CPU) bool rcu_is_nocb_cpu(int cpu); #else static inline bool rcu_is_nocb_cpu(int cpu) { return false; } #endif That clearly distinguishes the three cases: all, some, none. > diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h > index 6e2ef4b2b920..39a50b918bff 100644 > --- a/kernel/rcu/tree_plugin.h > +++ b/kernel/rcu/tree_plugin.h > @@ -2101,6 +2101,7 @@ static void rcu_init_one_nocb(struct rcu_node *rnp) > init_waitqueue_head(&rnp->nocb_gp_wq[1]); > } > > +#ifndef CONFIG_RCU_NOCB_CPU_ALL > /* Is the specified CPU a no-CPUs CPU? */ > bool rcu_is_nocb_cpu(int cpu) > { > @@ -2108,6 +2109,7 @@ bool rcu_is_nocb_cpu(int cpu) > return cpumask_test_cpu(cpu, rcu_nocb_mask); > return false; > } > +#endif /* #ifndef CONFIG_RCU_NOCB_CPU_ALL */ > > /* > * Enqueue the specified string of rcu_head structures onto the specified > -- > 1.8.1.5 >