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=-6.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no 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 A6896C55178 for ; Sat, 7 Nov 2020 00:18:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 56AD12087E for ; Sat, 7 Nov 2020 00:18:51 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=joelfernandes.org header.i=@joelfernandes.org header.b="oSk0+kOV" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728237AbgKGASu (ORCPT ); Fri, 6 Nov 2020 19:18:50 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51916 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727178AbgKGASt (ORCPT ); Fri, 6 Nov 2020 19:18:49 -0500 Received: from mail-qt1-x842.google.com (mail-qt1-x842.google.com [IPv6:2607:f8b0:4864:20::842]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9BBAEC0613D3 for ; Fri, 6 Nov 2020 16:18:49 -0800 (PST) Received: by mail-qt1-x842.google.com with SMTP id m65so2083864qte.11 for ; Fri, 06 Nov 2020 16:18:49 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=joelfernandes.org; s=google; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=mEuB3gvASt9FZRX3Uf0tIzy1nrj8CxUyLUi9+Eco7Jk=; b=oSk0+kOVeFLyyilDKzK0YXNgJa+Bez2dGaVLQx+TbXj2QO8QIneSuhsQrRfpmhbZbP X1Wjj4NUit8vlY8R86LNzlPkbZGA1c3lv+cuX7Ei239fxXRASiqq1ggatTefjoc/M7Ts HyOcfhemDcEFFFO7Be7f7bK9UqGtP7fUIESWY= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=mEuB3gvASt9FZRX3Uf0tIzy1nrj8CxUyLUi9+Eco7Jk=; b=R8tAEp5/ePGJMfviNioQzauBA40jBVJZjf9HXCwjK2rMfeszpJQ0cUHfR/oWWHrqNI TAxmfMzI6J5XRz3Ry3QiPmFUrloW5WFRypus7yIydkV73gsgmC/PCKvlgWJq6KfyQ3xr 4k8Wthxd/PeNuI3TQBZYZqxpdK4lgGvWuq7aISiRJuvMcRd+DoCKS9JImh09TvVI+IP0 qWe1WfCl35FXvV7tqNPTJ67+6yRLABVu4e9m3hsg75Z1PW8pT8AG8iD02LiEwDTMjaoj 8JAr2hrV/q/TnziLcttHE1AUu3dUUnruyC14b3idZwKTKus68DzQSyvFeSXC1tahERFH ytzA== X-Gm-Message-State: AOAM5319ohjxGtIFfEnKA69DepEoMovbC0r/9L5M5657ESoNZMavdE7A GnscbziMdUUheztQwvnpYDrWFg== X-Google-Smtp-Source: ABdhPJyHhJKcS7H8fFVU8az99zO5YCIijZGYlNG+FPxC9qpuZZLqmnwG0NhmCgqyl7lrv8RbZLlj/w== X-Received: by 2002:ac8:7b3a:: with SMTP id l26mr3143780qtu.42.1604708328818; Fri, 06 Nov 2020 16:18:48 -0800 (PST) Received: from localhost ([2620:15c:6:411:cad3:ffff:feb3:bd59]) by smtp.gmail.com with ESMTPSA id n35sm1714123qtc.55.2020.11.06.16.18.48 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 06 Nov 2020 16:18:48 -0800 (PST) Date: Fri, 6 Nov 2020 19:18:47 -0500 From: Joel Fernandes To: "Paul E. McKenney" 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: <20201107001847.GD1397669@google.com> References: <20201103142603.1302207-1-joel@joelfernandes.org> <20201103142603.1302207-3-joel@joelfernandes.org> <20201104170133.GI3249@paulmck-ThinkPad-P72> <20201107000157.GB1397669@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201107000157.GB1397669@google.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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: ---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); }