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=-19.3 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 8C8AFC433E9 for ; Wed, 6 Jan 2021 00:42:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5E1BB230F9 for ; Wed, 6 Jan 2021 00:42:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727293AbhAFAmW (ORCPT ); Tue, 5 Jan 2021 19:42:22 -0500 Received: from mail.kernel.org ([198.145.29.99]:50568 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727176AbhAFAmV (ORCPT ); Tue, 5 Jan 2021 19:42:21 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id 848D1230FD; Wed, 6 Jan 2021 00:41:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1609893700; bh=q+WqZk3iFeqzY17TrD4gDRfHxp4dGLV2ms5irASR4eA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=NL7fBpVClHPS/IcUPUm3Maf0aB7PWVnHB/rn5ePZEyCTAj9EGmpeL6Ic6P0MZQtvy dG+UiYRm12MZ1ISn28EEt4vmg4KDQIuZgf1YbiO4yXVNPjbxRxHozB3/mNb8RNNQhc 4u0MUBNOHrlQlxLRA9wWmHDAGqXg4C2/snPje8aqgTWKEWVV4NqZuiXt3j5CCOFgyc 1L8+/jRmglrW8wTrUlpFSHFDkIpSQJFowCZf7DEIdXgdV/OyoSPdM8aaqd5djclrYD UweFvwfbCaq1KIeNFucFBzUHeyKjgjiMmWg/UCg8r8f4dEj+LGXFbghL+26PKjQy7Q nyn2AIrsWX6Xg== From: paulmck@kernel.org To: linux-kernel@vger.kernel.org Cc: kernel-team@fb.com, "Paul E. McKenney" , John Stultz , Thomas Gleixner , Stephen Boyd , Jonathan Corbet , Mark Rutland , Marc Zyngier Subject: [PATCH RFC clocksource 4/5] clocksource: Provide a module parameter to fuzz per-CPU clock checking Date: Tue, 5 Jan 2021 16:41:33 -0800 Message-Id: <20210106004134.11467-4-paulmck@kernel.org> X-Mailer: git-send-email 2.9.5 In-Reply-To: <20210106004013.GA11179@paulmck-ThinkPad-P72> References: <20210106004013.GA11179@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 Reported-by: Chris Mason Signed-off-by: Paul E. McKenney --- Documentation/admin-guide/kernel-parameters.txt | 9 +++++++++ kernel/time/clocksource.c | 10 +++++++++- 2 files changed, 18 insertions(+), 1 deletion(-) diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 15aa3fe..613ce32 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -593,6 +593,15 @@ times the value specified for inject_delay_freq of consecutive non-delays. + clocksource.inject_delay_shift_percpu= [KNL] + Shift count to obtain bit from CPU number to + determine whether to shift the time of the per-CPU + clock under test ahead or behind. For example, + setting this to the value four will result in + alternating groups of 16 CPUs shifting ahead and + the rest of the CPUs shifting behind. The default + value of -1 disable 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 23bcefe..67cf41c 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