From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751755AbeBBLmW (ORCPT ); Fri, 2 Feb 2018 06:42:22 -0500 Received: from smtp.codeaurora.org ([198.145.29.96]:60766 "EHLO smtp.codeaurora.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750773AbeBBLmN (ORCPT ); Fri, 2 Feb 2018 06:42:13 -0500 DMARC-Filter: OpenDMARC Filter v1.3.2 smtp.codeaurora.org 8524A606AC Authentication-Results: pdx-caf-mail.web.codeaurora.org; dmarc=none (p=none dis=none) header.from=codeaurora.org Authentication-Results: pdx-caf-mail.web.codeaurora.org; spf=none smtp.mailfrom=prsood@codeaurora.org To: viresh.kumar@linaro.org Cc: rjw@rjwysocki.net, linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org, gkohli@codeaurora.org, linux-arm-msm@vger.kernel.org From: Prateek Sood Subject: Query related to usage of cpufreq_suspend() & cpufreq_resume Message-ID: Date: Fri, 2 Feb 2018 17:11:58 +0530 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.5.0 MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Viresh, One scenario is there where a kernel panic is observed in cpufreq during suspend/resume. pm_suspend() suspend_devices_and_enter() dpm_suspend_start() dpm_prepare() Failure in dpm_prepare() happend with following dmesg: [ 3746.316062] PM: Device xyz not prepared for power transition: code -16 [ 3746.316071] PM: Some devices failed to suspend, or early wake event detected pm_suspend() suspend_devices_and_enter() dpm_suspend_start() dpm_prepare() //failed dpm_resume_end() dpm_resume() cpufreq_resume() cpufreq_start_governor() sugov_start() cpufreq_add_update_util_hook() After failure in dpm_prepare(), dpm_resume() called cpufreq_resume(). Corresponding cpufreq_suspend() was not called due to failure of dpm_prepare(). This resulted in WARN_ON(per_cpu(cpufreq_update_util_data, cpu)) in cpufreq_add_update_util_hook() and cpufreq_add_update_util_hook->func being inconsistent state. It caused crash in scheduler. Following are some of the ways to mitigate this issue. Could you please provide feedback on below two approaches or suugest a better way to fix this problem. -----------------------8<------------------------------ Co-developed-by: Gaurav Kohli Signed-off-by: Gaurav Kohli Signed-off-by: Prateek Sood diff --git a/drivers/base/power/main.c b/drivers/base/power/main.c index 02a497e..732e5a2 100644 --- a/drivers/base/power/main.c +++ b/drivers/base/power/main.c @@ -1038,6 +1038,7 @@ void dpm_resume(pm_message_t state) { struct device *dev; ktime_t starttime = ktime_get(); + bool valid_resume = false; trace_suspend_resume(TPS("dpm_resume"), state.event, true); might_sleep(); @@ -1055,6 +1056,7 @@ void dpm_resume(pm_message_t state) } while (!list_empty(&dpm_suspended_list)) { + valid_resume = true; dev = to_device(dpm_suspended_list.next); get_device(dev); if (!is_async(dev)) { @@ -1080,7 +1082,8 @@ void dpm_resume(pm_message_t state) async_synchronize_full(); dpm_show_time(starttime, state, 0, NULL); - cpufreq_resume(); + if (valid_resume) + cpufreq_resume(); trace_suspend_resume(TPS("dpm_resume"), state.event, false); } --------------------8<-------------------------------------- Signed-off-by: Prateek Sood diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c index 421f318..439eab8 100644 --- a/drivers/cpufreq/cpufreq.c +++ b/drivers/cpufreq/cpufreq.c @@ -1648,7 +1648,7 @@ void cpufreq_suspend(void) { struct cpufreq_policy *policy; - if (!cpufreq_driver) + if (!cpufreq_driver || cpufreq_suspended) return; if (!has_target() && !cpufreq_driver->suspend) @@ -1683,7 +1683,7 @@ void cpufreq_resume(void) struct cpufreq_policy *policy; int ret; - if (!cpufreq_driver) + if (!cpufreq_driver || !cpufreq_suspended) return; cpufreq_suspended = false; Thanks -- Qualcomm India Private Limited, on behalf of Qualcomm Innovation Center, Inc., is a member of Code Aurora Forum, a Linux Foundation Collaborative Project