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=-19.2 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT 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 84532C433B4 for ; Sun, 25 Apr 2021 22:47:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 595086115C for ; Sun, 25 Apr 2021 22:47:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231454AbhDYWrw (ORCPT ); Sun, 25 Apr 2021 18:47:52 -0400 Received: from mail.kernel.org ([198.145.29.99]:50710 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231247AbhDYWrv (ORCPT ); Sun, 25 Apr 2021 18:47:51 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 1226F6115B; Sun, 25 Apr 2021 22:47:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1619390831; bh=+O0eiRA5Zjw+Y/xlDDZZg0Zno4FGis6WQuqpt/9cJtc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=O2ETjFKIg/eA00vc2IbF2lWCGPtcvbxLsoGQoQfgesd/H73zkgvG37AK6VEEi45W6 1XAV788OLhV3Wk0RwGBKnbL/VG5u4+T/04unQMclWA6V2GFX9U9IMRbWBTa/EkG0zE GA9bCqq7uS28QGz8Dhnqj3R/+IKSyZeJBAtWTXtY0kT+Ez897qvFmyX0oEHJMZkPBr RDgRh4eBZ9BkP0zkE1zuSacCSaLfFVDrcwUX/hCWsBDURbLhjix6h67nqcYtcPEAs0 1zsq8TYD9h3rMxnpTYvKcerH4SyeecIS5arbkkQdPXjRDOEbcVCvNVniRWXyhbEoDR GwX5DAEz08XXg== Received: by paulmck-ThinkPad-P17-Gen-1.home (Postfix, from userid 1000) id D51C45C0126; Sun, 25 Apr 2021 15:47:10 -0700 (PDT) From: "Paul E. McKenney" To: tglx@linutronix.de Cc: linux-kernel@vger.kernel.org, john.stultz@linaro.org, sboyd@kernel.org, corbet@lwn.net, Mark.Rutland@arm.com, maz@kernel.org, kernel-team@fb.com, neeraju@codeaurora.org, ak@linux.intel.com, feng.tang@intel.com, zhengjun.xing@intel.com, "Paul E. McKenney" , Chris Mason Subject: [PATCH v10 clocksource 4/7] clocksource: Provide a module parameter to fuzz per-CPU clock checking Date: Sun, 25 Apr 2021 15:47:05 -0700 Message-Id: <20210425224709.1312655-4-paulmck@kernel.org> X-Mailer: git-send-email 2.31.1.189.g2e36527f23 In-Reply-To: <20210425224540.GA1312438@paulmck-ThinkPad-P17-Gen-1> References: <20210425224540.GA1312438@paulmck-ThinkPad-P17-Gen-1> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Code that checks for clock desynchronization must itself be tested, so create a new clocksource.inject_delay_shift_percpu= kernel boot parameter that adds or subtracts a large value from the check read, using the specified bit of the CPU ID to determine whether to add or to subtract. Cc: John Stultz Cc: Thomas Gleixner Cc: Stephen Boyd Cc: Jonathan Corbet Cc: Mark Rutland Cc: Marc Zyngier Cc: Andi Kleen Reported-by: Chris Mason [ paulmck: Apply Randy Dunlap feedback. ] Signed-off-by: Paul E. McKenney --- Documentation/admin-guide/kernel-parameters.txt | 16 ++++++++++++++++ kernel/time/clocksource.c | 10 +++++++++- 2 files changed, 25 insertions(+), 1 deletion(-) diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 7fff95bd5504..03a8c88a6bb9 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -599,6 +599,22 @@ will be five delay-free reads followed by three delayed reads. + clocksource.inject_delay_shift_percpu= [KNL] + Clocksource delay injection partitions the CPUs + into two sets, one whose clocks are moved ahead + and the other whose clocks are moved behind. + This kernel parameter selects the CPU-number + bit that determines which of these two sets the + corresponding CPU is placed into. For example, + setting this parameter to the value 4 will result + in the first set containing alternating groups + of 16 CPUs whose clocks are moved ahead, while + the second set will contain the rest of the CPUs, + whose clocks are moved behind. + + The default value of -1 disables this type of + error injection. + clocksource.max_read_retries= [KNL] Number of clocksource_watchdog() retries due to external delays before the clock will be marked diff --git a/kernel/time/clocksource.c b/kernel/time/clocksource.c index a8d73e1f9431..584433448226 100644 --- a/kernel/time/clocksource.c +++ b/kernel/time/clocksource.c @@ -196,6 +196,8 @@ static ulong inject_delay_period; module_param(inject_delay_period, ulong, 0644); static ulong inject_delay_repeat = 1; module_param(inject_delay_repeat, ulong, 0644); +static int inject_delay_shift_percpu = -1; +module_param(inject_delay_shift_percpu, int, 0644); static ulong max_read_retries = 3; module_param(max_read_retries, ulong, 0644); @@ -252,8 +254,14 @@ static cpumask_t cpus_behind; static void clocksource_verify_one_cpu(void *csin) { struct clocksource *cs = (struct clocksource *)csin; + s64 delta = 0; + int sign; - csnow_mid = cs->read(cs); + if (inject_delay_shift_percpu >= 0) { + sign = ((smp_processor_id() >> inject_delay_shift_percpu) & 0x1) * 2 - 1; + delta = sign * NSEC_PER_SEC; + } + csnow_mid = cs->read(cs) + delta; } static void clocksource_verify_percpu(struct clocksource *cs) -- 2.31.1.189.g2e36527f23