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=-12.5 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 3CBC6C4151A for ; Thu, 4 Mar 2021 01:09:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 172E364EE1 for ; Thu, 4 Mar 2021 01:09:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1451454AbhCDBHY (ORCPT ); Wed, 3 Mar 2021 20:07:24 -0500 Received: from mail.kernel.org ([198.145.29.99]:47752 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233907AbhCDAuO (ORCPT ); Wed, 3 Mar 2021 19:50:14 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id 1BC1B64EE1; Thu, 4 Mar 2021 00:49:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1614818972; bh=iYRf087/Opa8vsTGwHqy6vskuxxhSrmzQZv4QjvlXEg=; h=Date:From:To:Cc:Subject:Reply-To:References:In-Reply-To:From; b=JqUCyxltWlHhcA4tgHvOWRdzgj3L2ewNEAm6YdUsSDi/P9BRnMU+9FThXgcmg9yMJ UQdQolOFuY1WnUjNSBuVgas4PITDeMmFBimR9AFusMlcebxe4zrU24rASk5Pp6hkfK HCP+fypF4ByTOzNBTTfmVOISonToPAUoTejtXVitDCozA6IHqtW7k+z/tqmb6pWCPF kAB4OfcXBaFWceeljHNSe6sZ2lawVwey6N20TiDQkZ0jiN7YoyODi44/5lCXY1k/u8 MoB8WjTFmuI0J54ZHiw0aKj/rEX2BnYk9iGzvnoRNcSbqcSN7g8G6C7OuA/2IBpQ7R Z52Uu1ulprBzg== Received: by paulmck-ThinkPad-P72.home (Postfix, from userid 1000) id D97C83522591; Wed, 3 Mar 2021 16:49:31 -0800 (PST) Date: Wed, 3 Mar 2021 16:49:31 -0800 From: "Paul E. McKenney" To: linux-kernel@vger.kernel.org Cc: john.stultz@linaro.org, tglx@linutronix.de, sboyd@kernel.org, corbet@lwn.net, Mark.Rutland@arm.com, maz@kernel.org, kernel-team@fb.com, neeraju@codeaurora.org, ak@linux.intel.com Subject: [PATCH v5 clocksource] Do not mark clocks unstable due to delays for v5.13 Message-ID: <20210304004931.GA25461@paulmck-ThinkPad-P72> Reply-To: paulmck@kernel.org References: <20210106004013.GA11179@paulmck-ThinkPad-P72> <20210112004258.GA23158@paulmck-ThinkPad-P72> <20210202170437.GA23593@paulmck-ThinkPad-P72> <20210217212814.GA14952@paulmck-ThinkPad-P72> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210217212814.GA14952@paulmck-ThinkPad-P72> User-Agent: Mutt/1.9.4 (2018-02-28) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello! If there is a sufficient delay between reading the watchdog clock and the clock under test, the clock under test will be marked unstable through no fault of its own. This series checks for this, doing limited retries to get a good set of clock reads. If the clock is marked unstable and is marked as being per-CPU, cross-CPU synchronization is checked. This series also provides delay injection, which may be enabled via kernel boot parameters to test the checking for delays. Note that "sufficient delay" can be provided by SMIs, NMIs, and of course vCPU preemption. 1. Provide module parameters to inject delays in watchdog. 2. Retry clock read if long delays detected. 3. Check per-CPU clock synchronization when marked unstable. 4. Provide a module parameter to fuzz per-CPU clock checking. 5. Do pairwise clock-desynchronization checking. Changes since v4: o Rebased to v5.12-rc1. Changes since v3: o Rebased to v5.11. o Apply Randy Dunlap feedback. Changes since v2: o Rebased to v5.11-rc6. o Updated Cc: list. Changes since v1: o Applied feedback from Rik van Riel. o Rebased to v5.11-rc3. o Stripped "RFC" from the subject lines. Thanx, Paul ------------------------------------------------------------------------ Documentation/admin-guide/kernel-parameters.txt | 38 +++++ arch/x86/kernel/kvmclock.c | 2 arch/x86/kernel/tsc.c | 3 include/linux/clocksource.h | 2 kernel/time/clocksource.c | 174 +++++++++++++++++++++--- 5 files changed, 195 insertions(+), 24 deletions(-)