Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752721AbdHJPLt (ORCPT ); Thu, 10 Aug 2017 11:11:49 -0400 Received: from mail.ispras.ru ([83.149.199.45]:40978 "EHLO mail.ispras.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752457AbdHJPLr (ORCPT ); Thu, 10 Aug 2017 11:11:47 -0400 Subject: Re: Question about apds990x.ko To: Greg KH Cc: arnd@arndb.de, linux-kernel@vger.kernel.org, ldv-project@linuxtesting.org, Alexey Khoroshilov References: <6bd7a5d0-97ef-4e04-6914-9e287c7be767@ispras.ru> <20170810150755.GB8851@kroah.com> From: Anton Volkov Message-ID: Date: Thu, 10 Aug 2017 18:11:44 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.2.1 MIME-Version: 1.0 In-Reply-To: <20170810150755.GB8851@kroah.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1769 Lines: 43 The author of this driver as well as bh1770glc.ko is Samu Onkalo. His e-mail that was found as a contact in the module's source is invalid. I tried to add him previous time (Question about bh1770glc.ko). The message was not delivered then. On 10.08.2017 18:07, Greg KH wrote: > On Thu, Aug 10, 2017 at 05:57:30PM +0300, Anton Volkov wrote: >> Hello. >> >> While searching for races in the Linux kernel I've come across >> "drivers/misc/apds990x.ko" module. Here are questions that I came up with >> while analyzing results. Lines are given using the info from Linux v4.12. >> >> Consider the following case: >> >> Thread 1: Thread 2: >> apds990x_suspend >> apds990x_resume apds990x_irq >> -> apds990x_chip_on if (!pm_runtime_suspended >> (chip->client->dev)){ >> -> apds990x_configure if (status & APDS990X_ST_AINT) { >> chip->again_meas = 1 chip->again_meas = chip->again_next >> (apds990x.c: line 571) (apds990x.c: line 505) >> } >> } >> >> First question. Is this race feasible from your point of view? >> Second question. The check for the device suspension status >> (pm_runtime_suspended()) is present in the interrupt handler, but the >> functions pm_runtime_set_suspended / pm_runtime_set_active are not used in >> apds990x_suspend / apds990x_resume respectively. Do you know about any other >> method being used to make the modification of suspension status? > > No idea, sorry. Maybe the driver authors know? > > greg k-h > -- -- Anton Volkov Linux Verification Center, ISPRAS web: http://linuxtesting.org e-mail: avolkov@ispras.ru