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=-4.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS autolearn=unavailable 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 F24BDC169C4 for ; Sun, 3 Feb 2019 14:24:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C92D02084A for ; Sun, 3 Feb 2019 14:24:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730514AbfBCOV3 (ORCPT ); Sun, 3 Feb 2019 09:21:29 -0500 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:55790 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728500AbfBCOVW (ORCPT ); Sun, 3 Feb 2019 09:21:22 -0500 Received: from cable-78.29.236.164.coditel.net ([78.29.236.164] helo=deadeye) by shadbolt.decadent.org.uk with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.89) (envelope-from ) id 1gqIe8-0006QW-KO; Sun, 03 Feb 2019 14:21:20 +0000 Received: from ben by deadeye with local (Exim 4.92-RC4) (envelope-from ) id 1gqI9V-0006rJ-Cx; Sun, 03 Feb 2019 14:49:41 +0100 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, Denis Kirjanov , "MyungJoo Ham" , "Chanwoo Choi" , "Enric Balletbo i Serra" Date: Sun, 03 Feb 2019 14:45:08 +0100 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) X-Patchwork-Hint: ignore Subject: [PATCH 3.16 052/305] PM / devfreq: Fix devfreq_add_device() when drivers are built as modules. In-Reply-To: X-SA-Exim-Connect-IP: 78.29.236.164 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.16.63-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Enric Balletbo i Serra commit 23c7b54ca1cd1797ef39169ab85e6d46f1c2d061 upstream. When the devfreq driver and the governor driver are built as modules, the call to devfreq_add_device() or governor_store() 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 by adding a try_then_request_governor() function. First tries to find the governor, and then, if it is 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 Reviewed-by: Chanwoo Choi Signed-off-by: MyungJoo Ham [bwh: Backported to 3.16: - Use string literal instead of DEVFREQ_GOV_SIMPLE_ONDEMAND - Adjust context] Signed-off-by: Ben Hutchings --- drivers/devfreq/devfreq.c | 53 ++++++++++++++++++++++++++++++++++++--- 1 file changed, 49 insertions(+), 4 deletions(-) --- a/drivers/devfreq/devfreq.c +++ b/drivers/devfreq/devfreq.c @@ -11,6 +11,7 @@ */ #include +#include #include #include #include @@ -148,6 +149,49 @@ static struct devfreq_governor *find_dev return ERR_PTR(-ENODEV); } +/** + * try_then_request_governor() - Try to find the governor and request the + * module if is not found. + * @name: name of the governor + * + * Search the list of devfreq governors and request the module and try again + * if is not found. This can happen when both drivers (the governor driver + * and the driver that call devfreq_add_device) are built as modules. + * devfreq_list_lock should be held by the caller. Returns the matched + * governor's pointer. + */ +static struct devfreq_governor *try_then_request_governor(const char *name) +{ + struct devfreq_governor *governor; + int err = 0; + + if (IS_ERR_OR_NULL(name)) { + pr_err("DEVFREQ: %s: Invalid parameters\n", __func__); + return ERR_PTR(-EINVAL); + } + WARN(!mutex_is_locked(&devfreq_list_lock), + "devfreq_list_lock must be locked."); + + governor = find_devfreq_governor(name); + if (IS_ERR(governor)) { + mutex_unlock(&devfreq_list_lock); + + if (!strncmp(name, "simple_ondemand", + DEVFREQ_NAME_LEN)) + err = request_module("governor_%s", "simpleondemand"); + else + err = request_module("governor_%s", name); + /* Restore previous state before return */ + mutex_lock(&devfreq_list_lock); + if (err) + return NULL; + + governor = find_devfreq_governor(name); + } + + return governor; +} + /* Load monitoring helper functions for governors use */ /** @@ -499,9 +543,8 @@ struct devfreq *devfreq_add_device(struc mutex_unlock(&devfreq->lock); mutex_lock(&devfreq_list_lock); - list_add(&devfreq->node, &devfreq_list); - governor = find_devfreq_governor(devfreq->governor_name); + governor = try_then_request_governor(devfreq->governor_name); if (IS_ERR(governor)) { dev_err(dev, "%s: Unable to find governor for the device\n", __func__); @@ -517,12 +560,14 @@ struct devfreq *devfreq_add_device(struc __func__); goto err_init; } + + list_add(&devfreq->node, &devfreq_list); + mutex_unlock(&devfreq_list_lock); return devfreq; err_init: - list_del(&devfreq->node); mutex_unlock(&devfreq_list_lock); device_unregister(&devfreq->dev); @@ -798,7 +843,7 @@ static ssize_t governor_store(struct dev return -EINVAL; mutex_lock(&devfreq_list_lock); - governor = find_devfreq_governor(str_governor); + governor = try_then_request_governor(str_governor); if (IS_ERR(governor)) { ret = PTR_ERR(governor); goto out;