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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3FFAEC4332F for ; Thu, 15 Dec 2022 00:12:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229501AbiLOAMd (ORCPT ); Wed, 14 Dec 2022 19:12:33 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33678 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229854AbiLOAMF (ORCPT ); Wed, 14 Dec 2022 19:12:05 -0500 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D3F69554EB; Wed, 14 Dec 2022 16:04:36 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 90980B819B0; Thu, 15 Dec 2022 00:04:35 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 29EECC433D2; Thu, 15 Dec 2022 00:04:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1671062674; bh=6zdqv7Q8vPqfC1s6lXlTSp0z37xOGozf4pV1uPfE9b4=; h=Date:From:To:Cc:Subject:Reply-To:References:In-Reply-To:From; b=RcOMqxLsW0m76iF/DD3ge96L0j5jl66w4BTseO5hUDYboMtPpGretDEbf1SOCa+yF kbFICx8Xt3lpbvy4LJ/fhOJLj5Gr9LTuR7hEvyfAhAHQRBDnU+WaWdh4/av56iyFpb vSA0+GPkksYIOxt+gcRKvkzySm/tlikcAXxn99zw0NfXtgOkYy0pSxNZGhlmyI7dL6 Qv0rQGkspJ9gI/nsGWWAkAIJDMtUB3vjkyYD4k2Qk5ewVUGnO5XV/osN4TN82nauX3 jBypUpy0THA0Ql7SvLNlKRbq53BQbtvJmk3tBo5RMJzwBY37k/PoETxr5FjflQDeJt RKC4YjxrU3OGA== Received: by paulmck-ThinkPad-P17-Gen-1.home (Postfix, from userid 1000) id BC4125C0A6A; Wed, 14 Dec 2022 16:04:33 -0800 (PST) Date: Wed, 14 Dec 2022 16:04:33 -0800 From: "Paul E. McKenney" To: Joel Fernandes Cc: boqun.feng@gmail.com, frederic@kernel.org, neeraj.iitr10@gmail.com, urezki@gmail.com, rcu@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH RFC] srcu: Yet more detail for srcu_readers_active_idx_check() comments Message-ID: <20221215000433.GD4001@paulmck-ThinkPad-P17-Gen-1> Reply-To: paulmck@kernel.org References: <20221214191355.GA2596199@paulmck-ThinkPad-P17-Gen-1> <20221214212455.GA4001@paulmck-ThinkPad-P17-Gen-1> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Dec 14, 2022 at 11:14:48PM +0000, Joel Fernandes wrote: > On Wed, Dec 14, 2022 at 11:10 PM Joel Fernandes wrote: > > > > On Wed, Dec 14, 2022 at 11:07 PM Joel Fernandes wrote: > > > > > > On Wed, Dec 14, 2022 at 9:24 PM Paul E. McKenney wrote: > > > > > I also did not get why you care about readers that come and ago (you > > > > > mentioned the first reader seeing incorrect idx and the second reader > > > > > seeing the right flipped one, etc). Those readers are irrelevant > > > > > AFAICS since they came and went, and need not be waited on , right?. > > > > > > > > The comment is attempting to show (among other things) that we don't > > > > need to care about readers that come and go more than twice during that > > > > critical interval of time during the counter scans. > > > > > > Why do we need to care about readers that come and go even once? Once > > > they are gone, they have already done an unlock() and their RSCS is > > > over, so they need to be considered AFAICS. > > > > > > > Aargh, I meant: "so they need to be considered AFAICS". > > Trying again: "so they need not be considered AFAICS". Give or take counter wrap, which can make it appear that still-present readers have finished. > Anyway, my 1 year old son is sick so signing off for now. Thanks. Ouch! I hope he recovers quickly and completely!!! Thanx, Paul