Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751534AbdFIEhW (ORCPT ); Fri, 9 Jun 2017 00:37:22 -0400 Received: from mail-vk0-f51.google.com ([209.85.213.51]:34800 "EHLO mail-vk0-f51.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751043AbdFIEhU (ORCPT ); Fri, 9 Jun 2017 00:37:20 -0400 MIME-Version: 1.0 In-Reply-To: References: <1496916298-5909-1-git-send-email-binoy.jayan@linaro.org> <1496916298-5909-2-git-send-email-binoy.jayan@linaro.org> From: Binoy Jayan Date: Fri, 9 Jun 2017 10:07:17 +0530 Message-ID: Subject: Re: [PATCH 1/3] media: ngene: Replace semaphore cmd_mutex with mutex To: Arnd Bergmann Cc: Linux Kernel Mailing List , Rajendra , Mark Brown , Mauro Carvalho Chehab , Sakari Ailus , Julia Lawall , "Michael S. Tsirkin" , Cao jin , Linux Media Mailing List Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1381 Lines: 35 On 8 June 2017 at 20:40, Arnd Bergmann wrote: > On Thu, Jun 8, 2017 at 12:04 PM, Binoy Jayan wrote: >> The semaphore 'cmd_mutex' is used as a simple mutex, so >> it should be written as one. Semaphores are going away in the future. >> >> Signed-off-by: Binoy Jayan >> --- > >> @@ -1283,7 +1283,7 @@ static int ngene_load_firm(struct ngene *dev) >> >> static void ngene_stop(struct ngene *dev) >> { >> - down(&dev->cmd_mutex); >> + mutex_lock(&dev->cmd_mutex); >> i2c_del_adapter(&(dev->channel[0].i2c_adapter)); >> i2c_del_adapter(&(dev->channel[1].i2c_adapter)); >> ngwritel(0, NGENE_INT_ENABLE); > > Are you sure about this one? There is only one mutex_lock() and > then the structure gets freed without a corresponding mutex_unlock(). > > I suspect this violates some rules of mutexes, either when compile > testing with "make C=1", or when running with lockdep enabled. > > Can we actually have a concurrently held mutex at the time we > get here? If not, using mutex_destroy() in place of the down() > may be the right answer. I noticed the missing 'up' here, but may be semaphores do not have to adhere to that rule? Thank you for pointing out that. I'll check the concurrency part. By the way why do we need mutex_destoy? To debug an aberrate condition? Thanks, Binoy