From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965662AbbJ0RwQ (ORCPT ); Tue, 27 Oct 2015 13:52:16 -0400 Received: from mail-wi0-f182.google.com ([209.85.212.182]:35550 "EHLO mail-wi0-f182.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S965419AbbJ0Rcr (ORCPT ); Tue, 27 Oct 2015 13:32:47 -0400 From: =?UTF-8?q?B=C3=A1lint=20Czobor?= To: "Rafael J. Wysocki" , Viresh Kumar Cc: linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org, Todd Poynor , =?UTF-8?q?B=C3=A1lint=20Czobor?= Subject: [PATCH 36/70] cpufreq: interactive: fix race on timer restart on governor start Date: Tue, 27 Oct 2015 18:30:24 +0100 Message-Id: <1445967059-6897-36-git-send-email-czoborbalint@gmail.com> X-Mailer: git-send-email 1.7.9.5 In-Reply-To: <1445967059-6897-1-git-send-email-czoborbalint@gmail.com> References: <1445967059-6897-1-git-send-email-czoborbalint@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Todd Poynor Starting the governor, or restarting on a hotplugged-in CPU, can race with the timer start in idle, triggering a BUG on timer already pending. Start the timer before setting the enable flag, and use enable_sem to protect the sequence (and ensure correct order of the update to the enable flag). Delete any existing timer for safety. Change-Id: Ife77cf9fe099e8fd8543224cbf148c6722c2ffb0 Reported-by: Francisco Franco Signed-off-by: Todd Poynor Signed-off-by: Bálint Czobor --- drivers/cpufreq/cpufreq_interactive.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/drivers/cpufreq/cpufreq_interactive.c b/drivers/cpufreq/cpufreq_interactive.c index 74f5609..d22d162 100644 --- a/drivers/cpufreq/cpufreq_interactive.c +++ b/drivers/cpufreq/cpufreq_interactive.c @@ -919,17 +919,17 @@ static int cpufreq_governor_interactive(struct cpufreq_policy *policy, ktime_to_us(ktime_get()); pcpu->hispeed_validate_time = pcpu->floor_validate_time; - pcpu->governor_enabled = 1; - smp_wmb(); + down_write(&pcpu->enable_sem); expires = jiffies + usecs_to_jiffies(timer_rate); pcpu->cpu_timer.expires = expires; add_timer_on(&pcpu->cpu_timer, j); - if (timer_slack_val >= 0) { expires += usecs_to_jiffies(timer_slack_val); pcpu->cpu_slack_timer.expires = expires; add_timer_on(&pcpu->cpu_slack_timer, j); } + pcpu->governor_enabled = 1; + up_write(&pcpu->enable_sem); } /* -- 1.7.9.5