From owner-svn-src-all@FreeBSD.ORG Mon Jun 13 22:09:53 2011 Return-Path: Delivered-To: svn-src-all@FreeBSD.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id A82F41065675; Mon, 13 Jun 2011 22:09:53 +0000 (UTC) (envelope-from ken@kdm.org) Received: from nargothrond.kdm.org (nargothrond.kdm.org [70.56.43.81]) by mx1.freebsd.org (Postfix) with ESMTP id 719B98FC14; Mon, 13 Jun 2011 22:09:53 +0000 (UTC) Received: from nargothrond.kdm.org (localhost [127.0.0.1]) by nargothrond.kdm.org (8.14.2/8.14.2) with ESMTP id p5DM9q2b049010; Mon, 13 Jun 2011 16:09:52 -0600 (MDT) (envelope-from ken@nargothrond.kdm.org) Received: (from ken@localhost) by nargothrond.kdm.org (8.14.2/8.14.2/Submit) id p5DM9qmd049009; Mon, 13 Jun 2011 16:09:52 -0600 (MDT) (envelope-from ken) Date: Mon, 13 Jun 2011 16:09:52 -0600 From: "Kenneth D. Merry" To: Kostik Belousov Message-ID: <20110613220952.GA47928@nargothrond.kdm.org> References: <201106132121.p5DLL2Fp099153@svn.freebsd.org> <20110613213150.GC48734@deviant.kiev.zoral.com.ua> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20110613213150.GC48734@deviant.kiev.zoral.com.ua> User-Agent: Mutt/1.4.2i Cc: svn-src-head@FreeBSD.org, svn-src-all@FreeBSD.org, "Justin T. Gibbs" , src-committers@FreeBSD.org Subject: Re: svn commit: r223061 - head/sys/kern X-BeenThere: svn-src-all@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: "SVN commit messages for the entire src tree \(except for " user" and " projects" \)" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 13 Jun 2011 22:09:53 -0000 On Tue, Jun 14, 2011 at 00:31:50 +0300, Kostik Belousov wrote: > On Mon, Jun 13, 2011 at 09:21:02PM +0000, Justin T. Gibbs wrote: > > Author: gibbs > > Date: Mon Jun 13 21:21:02 2011 > > New Revision: 223061 > > URL: http://svn.freebsd.org/changeset/base/223061 > > > > Log: > > Fix a couple of race conditions in devstat(9) initialization. > > > > In devstat_new_entry(), there is no need to initialize the queue > > and the mutex in this function. There are ways to do static > > initialization on both, so use STAILQ_HEAD_INITIALIZER and > > MTX_SYSINIT to initialize the queue and the mutex. > > > > In devstat_alloc(), use an atomic test and set routine to guard > > making our entry in /dev. Using just a plain static variable > > creates a race condition on multiprocessor machines. If you > > attempt to create a second entry in devfs, the kernel will panic. > Devfs returns an error if MAKEDEV_CHECKNAME flag is supplied and > attempt is made to create the existing node. The static guard is > still useful, since make_dev() call is costly, but you can remove > the atomic, since the race should be of limited scope. Done, thanks for the suggestion! Ken -- Kenneth Merry ken@FreeBSD.org