From patchwork Mon Dec 18 01:15:32 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Rafael J. Wysocki" X-Patchwork-Id: 10118119 X-Patchwork-Delegate: rjw@sisk.pl Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 25F9C60392 for ; Mon, 18 Dec 2017 01:16:23 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id F3D6428DBB for ; Mon, 18 Dec 2017 01:16:22 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id E8A5428F9C; Mon, 18 Dec 2017 01:16:22 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.9 required=2.0 tests=BAYES_00,RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 9AA0828DBB for ; Mon, 18 Dec 2017 01:16:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757594AbdLRBQV (ORCPT ); Sun, 17 Dec 2017 20:16:21 -0500 Received: from cloudserver094114.home.net.pl ([79.96.170.134]:61508 "EHLO cloudserver094114.home.net.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757508AbdLRBQU (ORCPT ); Sun, 17 Dec 2017 20:16:20 -0500 Received: from 79.184.254.73.ipv4.supernova.orange.pl (79.184.254.73) (HELO aspire.rjw.lan) by serwer1319399.home.pl (79.96.170.134) with SMTP (IdeaSmtpServer 0.82) id 536ab8d4cebe5840; Mon, 18 Dec 2017 02:16:18 +0100 From: "Rafael J. Wysocki" To: Doug Smythies , 'Andy Tang' , 'Linux PM' Cc: 'Viresh Kumar' , 'Stratos Karafotis' Subject: [PATCH] cpufreq: governor: Ensure sufficiently large sampling intervals Date: Mon, 18 Dec 2017 02:15:32 +0100 Message-ID: <5893809.nB6uDLgMiy@aspire.rjw.lan> In-Reply-To: <002501d375d2$54f942c0$feebc840$@net> References: <002001d37577$9706a730$c513f590$@net> <002501d375d2$54f942c0$feebc840$@net> MIME-Version: 1.0 Sender: linux-pm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pm@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP From: Rafael J. Wysocki After commit aa7519af450d (cpufreq: Use transition_delay_us for legacy governors as well) the sampling_rate field of struct dbs_data may be less than the tick period which causes dbs_update() to produce incorrect results, so make the code ensure that the value of that field will always be sufficiently large. Fixes: aa7519af450d (cpufreq: Use transition_delay_us for legacy governors as well) Reported-by: Andy Tang Reported-by: Doug Smythies Signed-off-by: Rafael J. Wysocki Acked-by: Viresh Kumar --- drivers/cpufreq/cpufreq_governor.c | 19 ++++++++++++++++--- 1 file changed, 16 insertions(+), 3 deletions(-) Index: linux-pm/drivers/cpufreq/cpufreq_governor.c =================================================================== --- linux-pm.orig/drivers/cpufreq/cpufreq_governor.c +++ linux-pm/drivers/cpufreq/cpufreq_governor.c @@ -22,6 +22,8 @@ #include "cpufreq_governor.h" +#define CPUFREQ_DBS_MIN_SAMPLING_INTERVAL (2 * TICK_NSEC / NSEC_PER_USEC) + static DEFINE_PER_CPU(struct cpu_dbs_info, cpu_dbs); static DEFINE_MUTEX(gov_dbs_data_mutex); @@ -47,11 +49,15 @@ ssize_t store_sampling_rate(struct gov_a { struct dbs_data *dbs_data = to_dbs_data(attr_set); struct policy_dbs_info *policy_dbs; + unsigned int sampling_interval; int ret; - ret = sscanf(buf, "%u", &dbs_data->sampling_rate); - if (ret != 1) + + ret = sscanf(buf, "%u", &sampling_interval); + if (ret != 1 || sampling_interval < CPUFREQ_DBS_MIN_SAMPLING_INTERVAL) return -EINVAL; + dbs_data->sampling_rate = sampling_interval; + /* * We are operating under dbs_data->mutex and so the list and its * entries can't be freed concurrently. @@ -430,7 +436,14 @@ int cpufreq_dbs_governor_init(struct cpu if (ret) goto free_policy_dbs_info; - dbs_data->sampling_rate = cpufreq_policy_transition_delay_us(policy); + /* + * The sampling interval should not be less than the transition latency + * of the CPU and it also cannot be too small for dbs_update() to work + * correctly. + */ + dbs_data->sampling_rate = max_t(unsigned int, + CPUFREQ_DBS_MIN_SAMPLING_INTERVAL, + cpufreq_policy_transition_delay_us(policy)); if (!have_governor_per_policy()) gov->gdbs_data = dbs_data;