Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933717AbcKGTEk (ORCPT ); Mon, 7 Nov 2016 14:04:40 -0500 Received: from smtp.codeaurora.org ([198.145.29.96]:49052 "EHLO smtp.codeaurora.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932916AbcKGTEh (ORCPT ); Mon, 7 Nov 2016 14:04:37 -0500 DMARC-Filter: OpenDMARC Filter v1.3.1 smtp.codeaurora.org 589896122D Authentication-Results: pdx-caf-mail.web.codeaurora.org; dmarc=none header.from=codeaurora.org Authentication-Results: pdx-caf-mail.web.codeaurora.org; spf=pass smtp.mailfrom=skannan@codeaurora.org Message-ID: <5820CE7E.40802@codeaurora.org> Date: Mon, 07 Nov 2016 10:57:02 -0800 From: Saravana Kannan User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130329 Thunderbird/17.0.5 MIME-Version: 1.0 To: Chanwoo Choi CC: "Rafael J. Wysocki" , MyungJoo Ham , Kyungmin Park , linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v3] PM / devfreq: Restart previous governor if new governor fails to start References: <1477509425-16936-1-git-send-email-skannan@codeaurora.org> In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2030 Lines: 57 On 10/26/2016 05:06 PM, Chanwoo Choi wrote: > Hi, > > On 2016년 10월 27일 04:17, Saravana Kannan wrote: >> If the new governor fails to start, switch back to old governor so that the >> devfreq state is not left in some weird limbo. >> >> Signed-off-by: Saravana Kannan >> --- >> * Fix NULL deref for real this time. >> * Addressed some style preferences. >> >> drivers/devfreq/devfreq.c | 13 +++++++++++-- >> 1 file changed, 11 insertions(+), 2 deletions(-) >> >> diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c >> index bf3ea76..77c41a5 100644 >> --- a/drivers/devfreq/devfreq.c >> +++ b/drivers/devfreq/devfreq.c >> @@ -919,7 +919,7 @@ static ssize_t governor_store(struct device *dev, struct device_attribute *attr, >> struct devfreq *df = to_devfreq(dev); >> int ret; >> char str_governor[DEVFREQ_NAME_LEN + 1]; >> - struct devfreq_governor *governor; >> + const struct devfreq_governor *governor, *prev_governor; >> >> ret = sscanf(buf, "%" __stringify(DEVFREQ_NAME_LEN) "s", str_governor); >> if (ret != 1) >> @@ -944,12 +944,21 @@ static ssize_t governor_store(struct device *dev, struct device_attribute *attr, >> goto out; >> } >> } >> + prev_governor = df->governor; >> df->governor = governor; >> strncpy(df->governor_name, governor->name, DEVFREQ_NAME_LEN); >> ret = df->governor->event_handler(df, DEVFREQ_GOV_START, NULL); >> - if (ret) >> + if (ret) { >> dev_warn(dev, "%s: Governor %s not started(%d)\n", >> __func__, df->governor->name, ret); >> + if (prev_governor) { > > I think that prev_governor is always set. You don't need to check it. > Why do check it? Not true. Even higher up in this function, we check if df->governor != NULL. Simple example would be that the default governor passed in while adding the device isn't compiled in. Thanks, Saravana -- Qualcomm Innovation Center, Inc. The Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project