From mboxrd@z Thu Jan 1 00:00:00 1970 From: Bo Yan Subject: [PATCH v2] cpufreq: skip cpufreq resume if it's not suspended Date: Thu, 25 Jan 2018 11:15:45 -0800 Message-ID: <1516907745-13508-1-git-send-email-byan@nvidia.com> References: <1744712.rO4QOLozun@aspire.rjw.lan> Mime-Version: 1.0 Content-Type: text/plain Return-path: Received: from hqemgate15.nvidia.com ([216.228.121.64]:17444 "EHLO hqemgate15.nvidia.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751108AbeAYTPu (ORCPT ); Thu, 25 Jan 2018 14:15:50 -0500 In-Reply-To: <1744712.rO4QOLozun@aspire.rjw.lan> Sender: linux-pm-owner@vger.kernel.org List-Id: linux-pm@vger.kernel.org To: rjw@rjwysocki.net, pavel@ucw.cz, len.brown@intel.com Cc: linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org, Bo Yan cpufreq_resume can be called even without preceding cpufreq_suspend. This can happen in following scenario: suspend_devices_and_enter --> dpm_suspend_start --> dpm_prepare --> device_prepare : this function errors out --> dpm_suspend: this is skipped due to dpm_prepare failure this means cpufreq_suspend is skipped over --> goto Recover_platform, due to previous error --> goto Resume_devices --> dpm_resume_end --> dpm_resume --> cpufreq_resume In case schedutil is used as frequency governor, cpufreq_resume will eventually call sugov_start, which does following: memset(sg_cpu, 0, sizeof(*sg_cpu)); .... This effectively erases function pointer for frequency update, causing crash later on. The function pointer would have been set correctly if subsequent cpufreq_add_update_util_hook runs successfully, but that function returns earlier because cpufreq_suspend was not called: if (WARN_ON(per_cpu(cpufreq_update_util_data, cpu))) return; Ideally, suspend should succeed, then things will be fine. But even in case of suspend failure, system should not crash. The fix is to check the pm_transition status in dpm_resume. if pm_transition.event == PMSG_ON, we know for sure dpm_suspend has not been called, so do not call cpufreq_resume. Signed-off-by: Bo Yan --- drivers/base/power/main.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/drivers/base/power/main.c b/drivers/base/power/main.c index 08744b572af6..39829d7a9311 100644 --- a/drivers/base/power/main.c +++ b/drivers/base/power/main.c @@ -921,6 +921,7 @@ static void async_resume(void *data, async_cookie_t cookie) void dpm_resume(pm_message_t state) { struct device *dev; + bool suspended = (pm_transition.event != PM_EVENT_ON); ktime_t starttime = ktime_get(); trace_suspend_resume(TPS("dpm_resume"), state.event, true); @@ -964,7 +965,8 @@ void dpm_resume(pm_message_t state) async_synchronize_full(); dpm_show_time(starttime, state, 0, NULL); - cpufreq_resume(); + if (likely(suspended)) + cpufreq_resume(); trace_suspend_resume(TPS("dpm_resume"), state.event, false); } -- 2.7.4