From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.7 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,UNPARSEABLE_RELAY,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0E310C433EF for ; Tue, 19 Jun 2018 08:23:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B79C62075E for ; Tue, 19 Jun 2018 08:23:03 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B79C62075E Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=collabora.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756569AbeFSIXB (ORCPT ); Tue, 19 Jun 2018 04:23:01 -0400 Received: from bhuna.collabora.co.uk ([46.235.227.227]:59410 "EHLO bhuna.collabora.co.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756498AbeFSIW5 (ORCPT ); Tue, 19 Jun 2018 04:22:57 -0400 Received: from [127.0.0.1] (localhost [127.0.0.1]) (Authenticated sender: eballetbo) with ESMTPSA id 6E745263BB3 Subject: Re: [PATCH] PM / devfreq: Fix devfreq_add_device() when drivers are built as modules. To: Enric Balletbo Serra , cwchoi00@gmail.com Cc: linux-kernel , kernel@collabora.com, Chanwoo Choi , Kyungmin Park , MyungJoo Ham , Linux PM list References: <20180615100452.17466-1-enric.balletbo@collabora.com> From: Enric Balletbo i Serra Message-ID: <7eff02c1-3d78-de08-19ab-a4a45c491a86@collabora.com> Date: Tue, 19 Jun 2018 10:22:52 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.8.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-GB Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Chanwoo, On 18/06/18 11:02, Enric Balletbo Serra wrote: > Hi Chanwoo, > Missatge de Chanwoo Choi del dia dg., 17 de juny > 2018 a les 5:50: >> >> Hi Enric, >> >> This issue will happen on the position to use find_devfreq_governor() >> as following: >> - devfreq_add_governora() and governor_store() >> >> If device driver with module type after loaded want to change the >> scaling governor, >> new governor might be not yet loaded. So, devfreq bettero to consider this case >> in the find_devfreq_governor(). >> > Ok, I'll move there and send a v2. > I tried your suggestion but I found one problem, if I move the code in find_devfreq_governor it end up with a deadlock. The reason is the following calls. devfreq_add_device find_devfreq_governor (!!!) request_module devfreq_simple_ondemand_init devfreq_add_governor find_devfreq_governor (DEADLOCK) So I am wondering if shouldn't be more easy fix the issue in both places, devfreq_add_device and governor_store. To devfreq_add_device devfreq_add_device governor = find_devfreq_governor if (IS_ERR(governor) { request_module governor = find_devfreq_governor if (IS_ERR(governor) return ERR_PTR(governor) } And the same for governor_store governor_store governor = find_devfreq_governor if (IS_ERR(governor) { request_module governor = find_devfreq_governor if (IS_ERR(governor) return ERR_PTR(governor) } Maybe all can go in a new function try_find_devfreq_governor_then_request Other suggestions? - Enric > Thanks > Enric. > > >> 2018-06-15 19:04 GMT+09:00 Enric Balletbo i Serra >> : >>> When the devfreq driver and the governor driver are built as modules, >>> the call to devfreq_add_device() fails because the governor driver is >>> not loaded at the time the devfreq driver loads. The devfreq driver has >>> a build dependency on the governor but also should have a runtime >>> dependency. We need to make sure that the governor driver is loaded >>> before the devfreq driver. >>> >>> This patch fixes this bug in devfreq_add_device(). First tries to find >>> the governor, and then, if was not found, it requests the module and >>> tries again. >>> >>> Fixes: 1b5c1be2c88e (PM / devfreq: map devfreq drivers to governor using name) >>> Signed-off-by: Enric Balletbo i Serra >>> --- >>> >>> drivers/devfreq/devfreq.c | 36 +++++++++++++++++++++++++++++++----- >>> 1 file changed, 31 insertions(+), 5 deletions(-) >>> >>> diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c >>> index fe2af6aa88fc..1d917f043e30 100644 >>> --- a/drivers/devfreq/devfreq.c >>> +++ b/drivers/devfreq/devfreq.c >>> @@ -11,6 +11,7 @@ >>> */ >>> >>> #include >>> +#include >>> #include >>> #include >>> #include >>> @@ -648,10 +649,35 @@ struct devfreq *devfreq_add_device(struct device *dev, >>> >>> governor = find_devfreq_governor(devfreq->governor_name); >>> if (IS_ERR(governor)) { >>> - dev_err(dev, "%s: Unable to find governor for the device\n", >>> - __func__); >>> - err = PTR_ERR(governor); >>> - goto err_init; >>> + list_del(&devfreq->node); >>> + mutex_unlock(&devfreq_list_lock); >>> + >>> + /* >>> + * If the governor is not found, then request the module and >>> + * try again. This can happen when both drivers (the governor >>> + * driver and the driver that calls devfreq_add_device) are >>> + * built as modules. >>> + */ >>> + if (!strncmp(devfreq->governor_name, >>> + DEVFREQ_GOV_SIMPLE_ONDEMAND, DEVFREQ_NAME_LEN)) >>> + err = request_module("governor_%s", "simpleondemand"); >>> + else >>> + err = request_module("governor_%s", >>> + devfreq->governor_name); >>> + if (err) >>> + goto err_unregister; >>> + >>> + mutex_lock(&devfreq_list_lock); >>> + list_add(&devfreq->node, &devfreq_list); >>> + >>> + governor = find_devfreq_governor(devfreq->governor_name); >>> + if (IS_ERR(governor)) { >>> + dev_err(dev, >>> + "%s: Unable to find governor for the device\n", >>> + __func__); >>> + err = PTR_ERR(governor); >>> + goto err_init; >>> + } >>> } >>> >>> devfreq->governor = governor; >>> @@ -669,7 +695,7 @@ struct devfreq *devfreq_add_device(struct device *dev, >>> err_init: >>> list_del(&devfreq->node); >>> mutex_unlock(&devfreq_list_lock); >>> - >>> +err_unregister: >>> device_unregister(&devfreq->dev); >>> err_dev: >>> if (devfreq) >>> -- >>> 2.17.1 >>> >> >> >> >> -- >> Best Regards, >> Chanwoo Choi >> Samsung Electronics >