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 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9702CC433FE for ; Mon, 18 Oct 2021 06:08:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 753C9610C7 for ; Mon, 18 Oct 2021 06:08:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230169AbhJRGKj (ORCPT ); Mon, 18 Oct 2021 02:10:39 -0400 Received: from mail.kernel.org ([198.145.29.99]:59458 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229533AbhJRGKi (ORCPT ); Mon, 18 Oct 2021 02:10:38 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 8F1EE610A6; Mon, 18 Oct 2021 06:08:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1634537307; bh=r04T2c+9oBcdiXKL4Xe8gxRyhRIfiFS5MF915UNBWeg=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=mbe79Fr3OfSob3grAPxj2XjntzeEBJWPotyEIQ2cyZDKhfk9QOJrWsZEX6nIwzZHL v7n79QVfbaxauuq51wmKpbJ/yh8CZSJmPu6AaZRzIAM+sp/Ym9u6vwvGzw7D5FeLmX tKpK1fgd8J62SQvEGmvpmNToitvEHdF/JB0+klVY= Date: Mon, 18 Oct 2021 08:08:21 +0200 From: Greg KH To: David Lechner Cc: linux-iio@vger.kernel.org, William Breathitt Gray , linux-kernel@vger.kernel.org Subject: Re: [PATCH] counter: drop chrdev_lock Message-ID: References: <20211017185521.3468640-1-david@lechnology.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20211017185521.3468640-1-david@lechnology.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Oct 17, 2021 at 01:55:21PM -0500, David Lechner wrote: > This removes the chrdev_lock from the counter subsystem. This was > intended to prevent opening the chrdev more than once. However, this > doesn't work in practice since userspace can duplicate file descriptors > and pass file descriptors to other processes. Since this protection > can't be relied on, it is best to just remove it. Much better, thanks! One remaining question: > --- a/include/linux/counter.h > +++ b/include/linux/counter.h > @@ -297,7 +297,6 @@ struct counter_ops { > * @events: queue of detected Counter events > * @events_wait: wait queue to allow blocking reads of Counter events > * @events_lock: lock to protect Counter events queue read operations > - * @chrdev_lock: lock to limit chrdev to a single open at a time > * @ops_exist_lock: lock to prevent use during removal Why do you still need 2 locks for the same structure? thanks, greg k-h