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=-19.0 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,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 6691CC433ED for ; Fri, 2 Apr 2021 22:49:20 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 22EFF61179 for ; Fri, 2 Apr 2021 22:49:20 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236013AbhDBWtT (ORCPT ); Fri, 2 Apr 2021 18:49:19 -0400 Received: from mail.kernel.org ([198.145.29.99]:53384 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235598AbhDBWtK (ORCPT ); Fri, 2 Apr 2021 18:49:10 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id EEA66611AF; Fri, 2 Apr 2021 22:49:08 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1617403749; bh=L1clwboYyCJtqcpbXjeqzxb+eYAfwahPE637W6Ox2ak=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=W0D2ampUtjHQqqnSPSELMdPd5xgwOEs24/Z6EkhXD0unP9xVLLohV21Fbn6ztjEre teqDLMXpfq06Ak7wRciE7wvBz9To0vcdzVn1dU0ERLVOpQ4eWm17Q7NvwE2ZpsauwM imT9qDjSWBKOcc7FZlyg19eWgyNQhiFuxZ+eJ2yFY6VQyjovGCdw/peH/jLLvYyFNQ Gv9pk6bsfjWFll9Ub0QrfU5/w2yLGKmhEjA3ErEIbQF422SyD/OEdzsxVHYhfP/bzH WcKkDR37IeoSvowvmZnlHowaGC6c9R1Ugv/OKe9T+G2Akp1hroITnzLUoT9wK5D+xc JaMeTGGFl5gKw== From: paulmck@kernel.org 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, "Paul E. McKenney" Subject: [PATCH v7 clocksource 4/5] clocksource: Provide a module parameter to fuzz per-CPU clock checking Date: Fri, 2 Apr 2021 15:49:05 -0700 Message-Id: <20210402224906.3912-4-paulmck@kernel.org> X-Mailer: git-send-email 2.9.5 In-Reply-To: <20210402224828.GA3683@paulmck-ThinkPad-P72> References: <20210402224828.GA3683@paulmck-ThinkPad-P72> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: "Paul E. McKenney" Code that checks for clock desynchronization must itself be tested, so this commit creates 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 fc57952..f9da90f 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -599,6 +599,22 @@ times the value specified for inject_delay_freq of consecutive non-delays. + 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 663bc53..df48416 100644 --- a/kernel/time/clocksource.c +++ b/kernel/time/clocksource.c @@ -190,6 +190,8 @@ static int inject_delay_freq; module_param(inject_delay_freq, int, 0644); static int inject_delay_run = 1; module_param(inject_delay_run, int, 0644); +static int inject_delay_shift_percpu = -1; +module_param(inject_delay_shift_percpu, int, 0644); static int max_read_retries = 3; module_param(max_read_retries, int, 0644); @@ -219,8 +221,14 @@ static cpumask_t cpus_behind; static void clocksource_verify_one_cpu(void *csin) { struct clocksource *cs = (struct clocksource *)csin; + s64 delta = 0; + int sign; - __this_cpu_write(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; + } + __this_cpu_write(csnow_mid, cs->read(cs) + delta); } static void clocksource_verify_percpu_wq(struct work_struct *unused) -- 2.9.5