From patchwork Wed Jun 10 13:01:13 2015 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Hans de Goede X-Patchwork-Id: 6579341 Return-Path: X-Original-To: patchwork-linux-acpi@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork2.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.136]) by patchwork2.web.kernel.org (Postfix) with ESMTP id DCBEDC0020 for ; Wed, 10 Jun 2015 13:02:33 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id DFABA205FD for ; Wed, 10 Jun 2015 13:02:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E16B0205F9 for ; Wed, 10 Jun 2015 13:02:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933626AbbFJNCb (ORCPT ); Wed, 10 Jun 2015 09:02:31 -0400 Received: from mx1.redhat.com ([209.132.183.28]:48132 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933244AbbFJNCa (ORCPT ); Wed, 10 Jun 2015 09:02:30 -0400 Received: from int-mx14.intmail.prod.int.phx2.redhat.com (int-mx14.intmail.prod.int.phx2.redhat.com [10.5.11.27]) by mx1.redhat.com (Postfix) with ESMTPS id 2B7F935010C; Wed, 10 Jun 2015 13:02:30 +0000 (UTC) Received: from shalem.localdomain.com (vpn1-4-95.ams2.redhat.com [10.36.4.95]) by int-mx14.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id t5AD1YLI026315; Wed, 10 Jun 2015 09:02:26 -0400 From: Hans de Goede To: Darren Hart , "Rafael J. Wysocki" Cc: Ben Skeggs , Azael Avalos , Corentin Chary , Lee Chun-Yi , Cezary Jackiewicz , Matthew Garrett , =?UTF-8?q?Pali=20Roh=C3=A1r?= , Ike Panhc , Anisse Astier , Mattia Dongili , Henrique de Moraes Holschuh , platform-driver-x86@vger.kernel.org, ibm-acpi-devel@lists.sourceforge.net, acpi4asus-user@lists.sourceforge.net, dri-devel@lists.freedesktop.org, Aaron Lu , linux-acpi@vger.kernel.org, Hans de Goede Subject: [PATCH 13/32] acpi-video: Fix acpi_video _register vs _unregister_backlight race Date: Wed, 10 Jun 2015 15:01:13 +0200 Message-Id: <1433941292-21530-14-git-send-email-hdegoede@redhat.com> In-Reply-To: <1433941292-21530-1-git-send-email-hdegoede@redhat.com> References: <1433941292-21530-1-git-send-email-hdegoede@redhat.com> X-Scanned-By: MIMEDefang 2.68 on 10.5.11.27 Sender: linux-acpi-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-acpi@vger.kernel.org X-Spam-Status: No, score=-6.9 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_HI, T_RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=unavailable version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP It is possible for a native backlight driver to load while acpi_video_register is running, which may lead to acpi_video_unregister_backlight being called while acpi_video_register is running and the 2 racing against eachother. The register_count variable protects against this, but not in a thread safe manner, this commit adds locking to make this thread safe. Signed-off-by: Hans de Goede --- drivers/acpi/video.c | 43 +++++++++++++++++++++---------------------- 1 file changed, 21 insertions(+), 22 deletions(-) diff --git a/drivers/acpi/video.c b/drivers/acpi/video.c index b8053a8..fcc7c2e 100644 --- a/drivers/acpi/video.c +++ b/drivers/acpi/video.c @@ -79,6 +79,7 @@ static bool allow_duplicates; module_param(allow_duplicates, bool, 0644); static int register_count; +static DEFINE_MUTEX(register_count_mutex); static struct mutex video_list_lock; static struct list_head video_bus_head; static int acpi_video_bus_add(struct acpi_device *device); @@ -1931,14 +1932,15 @@ static int __init intel_opregion_present(void) int acpi_video_register(void) { - int ret; + int ret = 0; + mutex_lock(®ister_count_mutex); if (register_count) { /* * if the function of acpi_video_register is already called, * don't register the acpi_vide_bus again and return no error. */ - return 0; + goto leave; } mutex_init(&video_list_lock); @@ -1948,7 +1950,7 @@ int acpi_video_register(void) ret = acpi_bus_register_driver(&acpi_video_bus); if (ret) - return ret; + goto leave; /* * When the acpi_video_bus is loaded successfully, increase @@ -1956,24 +1958,20 @@ int acpi_video_register(void) */ register_count = 1; - return 0; +leave: + mutex_unlock(®ister_count_mutex); + return ret; } EXPORT_SYMBOL(acpi_video_register); void acpi_video_unregister(void) { - if (!register_count) { - /* - * If the acpi video bus is already unloaded, don't - * unload it again and return directly. - */ - return; + mutex_lock(®ister_count_mutex); + if (register_count) { + acpi_bus_unregister_driver(&acpi_video_bus); + register_count = 0; } - acpi_bus_unregister_driver(&acpi_video_bus); - - register_count = 0; - - return; + mutex_unlock(®ister_count_mutex); } EXPORT_SYMBOL(acpi_video_unregister); @@ -1981,13 +1979,14 @@ void acpi_video_unregister_backlight(void) { struct acpi_video_bus *video; - if (!register_count) - return; - - mutex_lock(&video_list_lock); - list_for_each_entry(video, &video_bus_head, entry) - acpi_video_bus_unregister_backlight(video); - mutex_unlock(&video_list_lock); + mutex_lock(®ister_count_mutex); + if (register_count) { + mutex_lock(&video_list_lock); + list_for_each_entry(video, &video_bus_head, entry) + acpi_video_bus_unregister_backlight(video); + mutex_unlock(&video_list_lock); + } + mutex_unlock(®ister_count_mutex); } EXPORT_SYMBOL(acpi_video_unregister_backlight);