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=-9.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable 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 35F70C388F7 for ; Mon, 9 Nov 2020 13:41:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E5DAC206B2 for ; Mon, 9 Nov 2020 13:41:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1604929267; bh=jX58UfIJGWVQV/mjB3kASkMntzspVbtxFRc6eguK0yM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=aHB9noAI80F74VQnzv0GAuoYlODlqEM2HKo2mbYwcL/h9FsJcATCXUz0KKFTwndTA mdTNN4LTLIyBmHAoMBM1LqDvA7Kc4ugJ1sFe1VfgEkb96QykZN9GuNKN3FKEv3LI/n 1uw3gdj0XsgJem1Y6iDs1qirJibJ6nq9Vh3QSsoA= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1733195AbgKINjO (ORCPT ); Mon, 9 Nov 2020 08:39:14 -0500 Received: from mail.kernel.org ([198.145.29.99]:56284 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730675AbgKINDl (ORCPT ); Mon, 9 Nov 2020 08:03:41 -0500 Received: from localhost (83-86-74-64.cable.dynamic.v4.ziggo.nl [83.86.74.64]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 9A43222203; Mon, 9 Nov 2020 13:02:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1604926980; bh=jX58UfIJGWVQV/mjB3kASkMntzspVbtxFRc6eguK0yM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=mAC4pzC99YafjCamYUEEJ5p3WncG/bQLqFVCZ9w+xzKlyDX0oBzXe2SaJsz4ssb31 PWWcYDw0hGKScznohN7bAzJwq68OtcNxzPsql5fgbpicr5XtfJES9K6xgNM3oQ6zc/ vCKl9qtpMdYGCf/T2xYsfg26MzLOKvb/Ow7SgjeY= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Joel Stanley , "Gautham R. Shenoy" , Michael Ellerman Subject: [PATCH 4.9 069/117] powerpc: Warn about use of smt_snooze_delay Date: Mon, 9 Nov 2020 13:54:55 +0100 Message-Id: <20201109125028.952500547@linuxfoundation.org> X-Mailer: git-send-email 2.29.2 In-Reply-To: <20201109125025.630721781@linuxfoundation.org> References: <20201109125025.630721781@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Joel Stanley commit a02f6d42357acf6e5de6ffc728e6e77faf3ad217 upstream. It's not done anything for a long time. Save the percpu variable, and emit a warning to remind users to not expect it to do anything. This uses pr_warn_once instead of pr_warn_ratelimit as testing 'ppc64_cpu --smt=off' on a 24 core / 4 SMT system showed the warning to be noisy, as the online/offline loop is slow. Fixes: 3fa8cad82b94 ("powerpc/pseries/cpuidle: smt-snooze-delay cleanup.") Cc: stable@vger.kernel.org # v3.14 Signed-off-by: Joel Stanley Acked-by: Gautham R. Shenoy Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/20200902000012.3440389-1-joel@jms.id.au Signed-off-by: Greg Kroah-Hartman --- arch/powerpc/kernel/sysfs.c | 42 +++++++++++++++++------------------------- 1 file changed, 17 insertions(+), 25 deletions(-) --- a/arch/powerpc/kernel/sysfs.c +++ b/arch/powerpc/kernel/sysfs.c @@ -28,29 +28,27 @@ static DEFINE_PER_CPU(struct cpu, cpu_devices); -/* - * SMT snooze delay stuff, 64-bit only for now - */ - #ifdef CONFIG_PPC64 -/* Time in microseconds we delay before sleeping in the idle loop */ -static DEFINE_PER_CPU(long, smt_snooze_delay) = { 100 }; +/* + * Snooze delay has not been hooked up since 3fa8cad82b94 ("powerpc/pseries/cpuidle: + * smt-snooze-delay cleanup.") and has been broken even longer. As was foretold in + * 2014: + * + * "ppc64_util currently utilises it. Once we fix ppc64_util, propose to clean + * up the kernel code." + * + * powerpc-utils stopped using it as of 1.3.8. At some point in the future this + * code should be removed. + */ static ssize_t store_smt_snooze_delay(struct device *dev, struct device_attribute *attr, const char *buf, size_t count) { - struct cpu *cpu = container_of(dev, struct cpu, dev); - ssize_t ret; - long snooze; - - ret = sscanf(buf, "%ld", &snooze); - if (ret != 1) - return -EINVAL; - - per_cpu(smt_snooze_delay, cpu->dev.id) = snooze; + pr_warn_once("%s (%d) stored to unsupported smt_snooze_delay, which has no effect.\n", + current->comm, current->pid); return count; } @@ -58,9 +56,9 @@ static ssize_t show_smt_snooze_delay(str struct device_attribute *attr, char *buf) { - struct cpu *cpu = container_of(dev, struct cpu, dev); - - return sprintf(buf, "%ld\n", per_cpu(smt_snooze_delay, cpu->dev.id)); + pr_warn_once("%s (%d) read from unsupported smt_snooze_delay\n", + current->comm, current->pid); + return sprintf(buf, "100\n"); } static DEVICE_ATTR(smt_snooze_delay, 0644, show_smt_snooze_delay, @@ -68,16 +66,10 @@ static DEVICE_ATTR(smt_snooze_delay, 064 static int __init setup_smt_snooze_delay(char *str) { - unsigned int cpu; - long snooze; - if (!cpu_has_feature(CPU_FTR_SMT)) return 1; - snooze = simple_strtol(str, NULL, 10); - for_each_possible_cpu(cpu) - per_cpu(smt_snooze_delay, cpu) = snooze; - + pr_warn("smt-snooze-delay command line option has no effect\n"); return 1; } __setup("smt-snooze-delay=", setup_smt_snooze_delay);