From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752965AbaBQXdk (ORCPT ); Mon, 17 Feb 2014 18:33:40 -0500 Received: from e32.co.us.ibm.com ([32.97.110.150]:55194 "EHLO e32.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751855AbaBQXdi (ORCPT ); Mon, 17 Feb 2014 18:33:38 -0500 Date: Mon, 17 Feb 2014 15:33:31 -0800 From: "Paul E. McKenney" To: Josh Triplett 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: <20140217233331.GR4250@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <20140217214007.GA6609@linux.vnet.ibm.com> <1392673227-7066-1-git-send-email-paulmck@linux.vnet.ibm.com> <20140217215053.GE7941@thin> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140217215053.GE7941@thin> User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 14021723-0928-0000-0000-000006C3BC12 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Feb 17, 2014 at 01:50:53PM -0800, Josh Triplett wrote: > 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 I like the change -- applied both it and your Reviewed-by. Thanx, Paul > > 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 > > >