From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752489AbeEOAf6 (ORCPT ); Mon, 14 May 2018 20:35:58 -0400 Received: from mail-pl0-f66.google.com ([209.85.160.66]:34896 "EHLO mail-pl0-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752382AbeEOAf5 (ORCPT ); Mon, 14 May 2018 20:35:57 -0400 X-Google-Smtp-Source: AB8JxZokpxgScq53NeGmBnzueImG9mbrUNKMwZ90qnQvYQ5ynG6Vg/DN6zrWQ8hCGSfV4KE50q9KfA== Date: Mon, 14 May 2018 17:35:55 -0700 From: Joel Fernandes To: "Paul E. McKenney" Cc: Steven Rostedt , linux-kernel@vger.kernel.org, Josh Triplett , Mathieu Desnoyers , Lai Jiangshan , byungchul.park@lge.com, kernel-team@android.com Subject: Re: [PATCH RFC 2/8] rcu: Clarify usage of cond_resched for tasks-RCU Message-ID: <20180515003555.GA209519@joelaf.mtv.corp.google.com> References: <20180514031541.67247-1-joel@joelfernandes.org> <20180514031541.67247-3-joel@joelfernandes.org> <20180514105454.45946ad3@gandalf.local.home> <20180514172205.GZ26088@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180514172205.GZ26088@linux.vnet.ibm.com> User-Agent: Mutt/1.9.2 (2017-12-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, May 14, 2018 at 10:22:05AM -0700, Paul E. McKenney wrote: > On Mon, May 14, 2018 at 10:54:54AM -0400, Steven Rostedt wrote: > > On Sun, 13 May 2018 20:15:35 -0700 > > "Joel Fernandes (Google)" wrote: > > > > > Recently we had a discussion about cond_resched unconditionally > > > recording a voluntary context switch [1]. > > > > > > Lets add a comment clarifying that how this API is to be used. > > > > > > [1] https://lkml.kernel.org/r/1526027434-21237-1-git-send-email-byungchul.park@lge.com > > > > > > Signed-off-by: Joel Fernandes (Google) > > > --- > > > include/linux/rcupdate.h | 11 ++++++++--- > > > 1 file changed, 8 insertions(+), 3 deletions(-) > > > > > > diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h > > > index 743226176350..a9881007ece6 100644 > > > --- a/include/linux/rcupdate.h > > > +++ b/include/linux/rcupdate.h > > > @@ -159,8 +159,12 @@ static inline void rcu_init_nohz(void) { } > > > } while (0) > > > > > > /* > > > - * Note a voluntary context switch for RCU-tasks benefit. This is a > > > - * macro rather than an inline function to avoid #include hell. > > > + * Note an attempt to perform a voluntary context switch for RCU-tasks benefit. > > > + * > > > + * This is called even in situations where a context switch didn't really > > > + * happen even though it was requested. The caller uses it to indicate > > > + * traversal of an RCU-tasks quiescent state. This is a macro rather than an > > > + * inline function to avoid #include hell. > > > > I don't know. I just don't like the wording. It sounds too much like > > it was written by someone that was confused for it being called when a > > context switch didn't occur ;-) True :) > > > > What about something more like: > > > > /* > > * This is called to denote a RCU-task quiescent state. It is placed at > > * voluntary preemption points, as RCU-task critical sections may not > > * perform voluntary preemption or scheduling calls. It does not matter > > * if the task is scheduled out or not, just that a voluntary preemption > > * may be done. > > */ > > s/RCU-task/RCU-tasks/ and I am good with this. Ok. I like Steve's comment better too. Btw, I see you just posted a change of the macro name from rcu_note_voluntary_context_switch_lite to rcu_tasks_qs which actually in itself is much more descriptive. Considering this, I feel the new name is quite self-documenting in itself. So I am more inclined to drop this patch in any series reposting, but let me know if you feel otherwise. thanks, - Joel