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=-6.3 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no 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 24A31C433E0 for ; Fri, 12 Feb 2021 07:43:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E2E5D64E57 for ; Fri, 12 Feb 2021 07:43:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230116AbhBLHmx (ORCPT ); Fri, 12 Feb 2021 02:42:53 -0500 Received: from mail.kernel.org ([198.145.29.99]:45122 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229710AbhBLHkH (ORCPT ); Fri, 12 Feb 2021 02:40:07 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id 4C36564DD6; Fri, 12 Feb 2021 07:39:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1613115566; bh=Gnb01Zlt7JlELKwkyjC2FjCJvYfhhVCdeifBUFpHFkU=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=KL4wts0ySgi1Xwt3fBv2gOOK8brB/EKoPhxiONVibR22++V9jH8K6h8b9LRwK7ocV 1+Tu3wDeyxmIdwAVLnlk5or5j5RtvJOetlhSfCxlRjG7GdTi4ue918mHrmZJiYuPB7 gnyOjGbFJsDcShugcQhC8sHkHkhtYmzFAVhdHrp8= Date: Fri, 12 Feb 2021 08:39:24 +0100 From: Greg KH To: min.li.xe@renesas.com Cc: derek.kiernan@xilinx.com, dragan.cvetic@xilinx.com, arnd@arndb.de, linux-kernel@vger.kernel.org Subject: Re: [PATCH net-next v2] misc: Add Renesas Synchronization Management Unit (SMU) support Message-ID: References: <1613092575-17311-1-git-send-email-min.li.xe@renesas.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1613092575-17311-1-git-send-email-min.li.xe@renesas.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Feb 11, 2021 at 08:16:15PM -0500, min.li.xe@renesas.com wrote: > +static int > +rsmu_open(struct inode *iptr, struct file *fptr) > +{ > + struct rsmu_cdev *rsmu; > + > + rsmu = container_of(iptr->i_cdev, struct rsmu_cdev, rsmu_cdev); > + if (!rsmu) > + return -EAGAIN; > + > + /* Only one open per device at a time */ > + if (!atomic_dec_and_test(&rsmu->open_count)) { > + atomic_inc(&rsmu->open_count); > + return -EBUSY; This does not do what you think it does, and does not prevent multiple applications from talking to your device at the same time. There is no need for this at all, as it does not work, sorry. If multiple apps talk to your device, it's their fault, not the kernel's fault, that things go wrong. And I thought that Arnd already told you to fix this? thanks, greg k-h