From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.6 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1741DC2D0A3 for ; Tue, 10 Nov 2020 01:39:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A21D320789 for ; Tue, 10 Nov 2020 01:39:51 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="Gqf3zDx/" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729983AbgKJBjv (ORCPT ); Mon, 9 Nov 2020 20:39:51 -0500 Received: from mail.kernel.org ([198.145.29.99]:33984 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727311AbgKJBjv (ORCPT ); Mon, 9 Nov 2020 20:39:51 -0500 Received: from paulmck-ThinkPad-P72.home (50-39-104-11.bvtn.or.frontiernet.net [50.39.104.11]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 6A459206ED; Tue, 10 Nov 2020 01:39:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1604972390; bh=k+hWNQSBN0IgkT54oBBMWOv2veTWxZebbVhtT7NKv7E=; h=Date:From:To:Cc:Subject:Reply-To:References:In-Reply-To:From; b=Gqf3zDx/U7UesWGNk0cys4tLUFkC0IxBaLXUKzF90+hgHYBIgRy34vBm3dWIQeYEd kWTkI68SF3/pO1daaABCBnMVocBu1NRYUFn95Uhqab1x8PPL2LGkfQ1Q/SZltt1DGz 0QE8XL3un7nfDuHmwuOa/8U23xpWZa1T2wY7FlfE= Received: by paulmck-ThinkPad-P72.home (Postfix, from userid 1000) id 0538235225E9; Mon, 9 Nov 2020 17:39:50 -0800 (PST) Date: Mon, 9 Nov 2020 17:39:49 -0800 From: "Paul E. McKenney" To: Joel Fernandes Cc: linux-kernel@vger.kernel.org, Frederic Weisbecker , Josh Triplett , Lai Jiangshan , Marco Elver , Mathieu Desnoyers , rcu@vger.kernel.org, Steven Rostedt , "Uladzislau Rezki (Sony)" , fweisbec@gmail.com, neeraj.iitr10@gmail.com Subject: Re: [PATCH v9 2/7] rcu/segcblist: Add counters to segcblist datastructure Message-ID: <20201110013949.GA16363@paulmck-ThinkPad-P72> Reply-To: paulmck@kernel.org References: <20201103142603.1302207-1-joel@joelfernandes.org> <20201103142603.1302207-3-joel@joelfernandes.org> <20201104170133.GI3249@paulmck-ThinkPad-P72> <20201107000157.GB1397669@google.com> <20201107001847.GD1397669@google.com> <20201107004815.GD3249@paulmck-ThinkPad-P72> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201107004815.GD3249@paulmck-ThinkPad-P72> User-Agent: Mutt/1.9.4 (2018-02-28) Precedence: bulk List-ID: X-Mailing-List: rcu@vger.kernel.org On Fri, Nov 06, 2020 at 04:48:15PM -0800, Paul E. McKenney wrote: > On Fri, Nov 06, 2020 at 07:18:47PM -0500, Joel Fernandes wrote: > > On Fri, Nov 06, 2020 at 07:01:57PM -0500, Joel Fernandes wrote: > > > On Wed, Nov 04, 2020 at 09:01:33AM -0800, Paul E. McKenney wrote: > > > > > > > A casual reader might be forgiven for being confused by the combination > > > > of "Return" in the above comment and the "void" function type below. > > > > So shouldn't this comment be something like "Add the specified number > > > > of callbacks to the specified segment..."? > > > > > > You are right, sorry and will fix it. > > > > > > > > @@ -330,11 +342,16 @@ void rcu_segcblist_extract_pend_cbs(struct rcu_segcblist *rsclp, > > > > > > > > > > if (!rcu_segcblist_pend_cbs(rsclp)) > > > > > return; /* Nothing to do. */ > > > > > + rclp->len = rcu_segcblist_get_seglen(rsclp, RCU_WAIT_TAIL) + > > > > > + rcu_segcblist_get_seglen(rsclp, RCU_NEXT_READY_TAIL) + > > > > > + rcu_segcblist_get_seglen(rsclp, RCU_NEXT_TAIL); > > > > > > > > This should be a "for" loop. Yes, the number and names of the segments > > > > hasn't changed for a good long time, but nothing like code as above to > > > > inspire Murphy to more mischief. :-/ > > > > > > > > Actually, why not put the summation in the existing "for" loop below? > > > > That would save a line of code in addition to providing less inspiration > > > > for Mr. Murphy. > > > > > > I can do that. Actually Frederic suggested the same thing but I was reluctant > > > as I felt it did not give much LOC benefit. Will revisit it. > > > > It reduces 1 line of code :) I changed it to the below, will update the patch: > > Thank you! And yes, I am much more concerned about the constraints on > Mr. Murphy than on the lines of code. ;-) And I have pulled in the updated commit, thank you all! Thanx, Paul > > ---8<----------------------- > > > > diff --git a/kernel/rcu/rcu_segcblist.c b/kernel/rcu/rcu_segcblist.c > > index 9b43d686b1f3..bff9b2253e50 100644 > > --- a/kernel/rcu/rcu_segcblist.c > > +++ b/kernel/rcu/rcu_segcblist.c > > @@ -101,7 +101,7 @@ static void rcu_segcblist_set_seglen(struct rcu_segcblist *rsclp, int seg, long > > WRITE_ONCE(rsclp->seglen[seg], v); > > } > > > > -/* Return number of callbacks in a segment of the segmented callback list. */ > > +/* Increase the numeric length of a segment by a specified amount. */ > > static void rcu_segcblist_add_seglen(struct rcu_segcblist *rsclp, int seg, long v) > > { > > WRITE_ONCE(rsclp->seglen[seg], rsclp->seglen[seg] + v); > > @@ -406,13 +406,12 @@ void rcu_segcblist_extract_pend_cbs(struct rcu_segcblist *rsclp, > > > > if (!rcu_segcblist_pend_cbs(rsclp)) > > return; /* Nothing to do. */ > > - rclp->len = rcu_segcblist_get_seglen(rsclp, RCU_WAIT_TAIL) + > > - rcu_segcblist_get_seglen(rsclp, RCU_NEXT_READY_TAIL) + > > - rcu_segcblist_get_seglen(rsclp, RCU_NEXT_TAIL); > > + rclp->len = 0; > > *rclp->tail = *rsclp->tails[RCU_DONE_TAIL]; > > rclp->tail = rsclp->tails[RCU_NEXT_TAIL]; > > WRITE_ONCE(*rsclp->tails[RCU_DONE_TAIL], NULL); > > for (i = RCU_DONE_TAIL + 1; i < RCU_CBLIST_NSEGS; i++) { > > + rclp->len += rcu_segcblist_get_seglen(rsclp, i); > > WRITE_ONCE(rsclp->tails[i], rsclp->tails[RCU_DONE_TAIL]); > > rcu_segcblist_set_seglen(rsclp, i, 0); > > }