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 05932C6FA8F for ; Wed, 30 Aug 2023 04:26:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S241983AbjH3E0Z (ORCPT ); Wed, 30 Aug 2023 00:26:25 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47608 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S241941AbjH3E0Q (ORCPT ); Wed, 30 Aug 2023 00:26:16 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id BB8221A3; Tue, 29 Aug 2023 21:26:11 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 4EA9760B00; Wed, 30 Aug 2023 04:26:11 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id A9CD3C433CB; Wed, 30 Aug 2023 04:26:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1693369570; bh=AGWJXrk34QfKCluDOSZ+qIvzRL4oGvSVWcF+e6r8B1s=; h=References:In-Reply-To:From:Date:Subject:To:Cc:From; b=W76f79cbhYNV1HaLoPPw6ChQQGlxQMXa6Vp/C4KsueuwI7mUTXe0THLP3uYWWaRCN 0PVw+pLlTrHd6SfMUoJ5lx7WJ+VL4Gmq1h815u0eHe1oNnsz06oU1E25l5BKXnqvWx BVKUvGLCZ8w7u9Ce+jKEoHC/Fw9DPhObOfnMlKs3RYSQR7QHe036dRSFMEXErUnSul hO4jyRTrtMLlJcvmZJ02TPvYGh/hC9rh9AKpU5dBHBGFFDuMwaFO+j2LtVZhxZ/ZlE w2tI57tvHEH04r9Ibc584u+JIIO4WcHA2fcVmwtc3/0fuXBqfEyv429/ZutNtL9B2f 3hnQj5L/L6FQA== Received: by mail-ej1-f51.google.com with SMTP id a640c23a62f3a-9a1de3417acso104949066b.0; Tue, 29 Aug 2023 21:26:10 -0700 (PDT) X-Gm-Message-State: AOJu0Yzcmgw6rkJWs1OPy3S1XYpUc/thgkqqRu9/R4KC4Jrlf3ucuKca fT6bGSOSYRDmnda7r5A7o/BgmiIdWGfqZf8nAD0= X-Google-Smtp-Source: AGHT+IENS5XKygzRXhsGNpGVrGYIDfiJDdTZarMiH5CvLSCIUBmBLXQNPKyN/6mMRxVY6PJNEKu/kFeu0CZnUzrVOzo= X-Received: by 2002:a17:906:7688:b0:9a5:a543:2744 with SMTP id o8-20020a170906768800b009a5a5432744mr1210778ejm.33.1693369568864; Tue, 29 Aug 2023 21:26:08 -0700 (PDT) MIME-Version: 1.0 References: <8792da20-a58e-4cc0-b3d2-231d5ade2242@paulmck-laptop> <24e34f50-32d2-4b67-8ec0-1034c984d035@paulmck-laptop> <20230825232807.GA97898@google.com> <2681134d-cc88-49a0-a1bc-4ec0816288f6@paulmck-laptop> <20230828133348.GA1553000@google.com> <142b4bff-6a2e-4ea0-928c-3cfe9befa403@paulmck-laptop> In-Reply-To: From: Huacai Chen Date: Wed, 30 Aug 2023 12:25:56 +0800 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH V4 2/2] rcu: Update jiffies in rcu_cpu_stall_reset() To: Joel Fernandes Cc: paulmck@kernel.org, Thomas Gleixner , Z qiang , Huacai Chen , Frederic Weisbecker , Neeraj Upadhyay , Josh Triplett , Boqun Feng , Ingo Molnar , John Stultz , Stephen Boyd , Steven Rostedt , Mathieu Desnoyers , Lai Jiangshan , Sergey Senozhatsky , rcu@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org, Binbin Zhou Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Aug 29, 2023 at 10:46=E2=80=AFPM Joel Fernandes wrote: > > On Tue, Aug 29, 2023 at 12:08=E2=80=AFAM Huacai Chen wrote: > > > > Hi, Joel, > > > > On Tue, Aug 29, 2023 at 4:47=E2=80=AFAM Joel Fernandes wrote: > > > > > > Hi Huacai, > > > > > > On Mon, Aug 28, 2023 at 11:13=E2=80=AFAM Huacai Chen wrote: > > > > > > > [...] > > > > > > > > > > > [Huacai] > > > > > > I also think the original patch should be OK, but I have anothe= r > > > > > > question: what will happen if the current GP ends before > > > > > > nr_fqs_jiffies_stall reaches zero? > > > > > > > > > > Nothing should happen. Stall detection only happens when a GP is = in > > > > > progress. If a new GP starts, it resets nr_fqs_jiffies_stall. > > > > > > > > > > Or can you elaborate your concern more? > > > > OK, I will test your patch these days. Maybe putting > > > > nr_fqs_jiffies_stall before jiffies_force_qs is better, because I > > > > think putting an 'int' between two 'long' is wasting space. :) > > > > > > That's a good point and I'll look into that. > > Another point, is it better to replace ULONG_MAX with ULONG_MAX/4 as > > Paul suggested? > > > > I could do that but I don't feel too strongly about it. I will keep it > at ULONG_MAX if it's OK with everyone. > > > > Meanwhile I pushed the patch out to my 6.4 stable tree for testing on= my fleet. > > > > > > Ideally, I'd like to change the stall detection test in the rcutortur= e > > > to actually fail rcutorture if stalls don't happen in time. But at > > > least I verified this manually using rcutorture. > > > > > > I should also add a documentation patch for stallwarn.rst to document > > > the understandable sensitivity of RCU stall detection to jiffies > > > updates (or lack thereof). Or if you have time, I'd appreciate suppor= t > > > on such a patch (not mandatory but I thought it would not hurt to > > > ask). > > > > > > Looking forward to how your testing goes as well! > > I have tested, it works for KGDB. > > Thanks! If you don't mind, I will add your Tested-by tag to the patch > and send it out soon. My tests also look good! You can add my Tested-by, but Reported-by should be "Binbin Zhou " Huacai > > > - Joel