From owner-svn-src-all@FreeBSD.ORG Mon Jun 13 21:21:03 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 08557106564A; Mon, 13 Jun 2011 21:21:03 +0000 (UTC) (envelope-from gibbs@FreeBSD.org) Received: from svn.freebsd.org (svn.freebsd.org [IPv6:2001:4f8:fff6::2c]) by mx1.freebsd.org (Postfix) with ESMTP id D2D8C8FC15; Mon, 13 Jun 2011 21:21:02 +0000 (UTC) Received: from svn.freebsd.org (localhost [127.0.0.1]) by svn.freebsd.org (8.14.4/8.14.4) with ESMTP id p5DLL2K3099155; Mon, 13 Jun 2011 21:21:02 GMT (envelope-from gibbs@svn.freebsd.org) Received: (from gibbs@localhost) by svn.freebsd.org (8.14.4/8.14.4/Submit) id p5DLL2Fp099153; Mon, 13 Jun 2011 21:21:02 GMT (envelope-from gibbs@svn.freebsd.org) Message-Id: <201106132121.p5DLL2Fp099153@svn.freebsd.org> From: "Justin T. Gibbs" Date: Mon, 13 Jun 2011 21:21:02 +0000 (UTC) To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org X-SVN-Group: head MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Cc: Subject: 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 21:21:03 -0000 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. Submitted by: kdm Reviewed by: gibbs Sponsored by: Spectra Logic Corporation MFC after: 1 week. Modified: head/sys/kern/subr_devstat.c Modified: head/sys/kern/subr_devstat.c ============================================================================== --- head/sys/kern/subr_devstat.c Mon Jun 13 21:03:27 2011 (r223060) +++ head/sys/kern/subr_devstat.c Mon Jun 13 21:21:02 2011 (r223061) @@ -49,8 +49,9 @@ static long devstat_generation = 1; static int devstat_version = DEVSTAT_VERSION; static int devstat_current_devnumber; static struct mtx devstat_mutex; +MTX_SYSINIT(devstat_mutex, &devstat_mutex, "devstat", MTX_DEF); -static struct devstatlist device_statq; +static struct devstatlist device_statq = STAILQ_HEAD_INITIALIZER(device_statq); static struct devstat *devstat_alloc(void); static void devstat_free(struct devstat *); static void devstat_add_entry(struct devstat *ds, const void *dev_name, @@ -70,13 +71,7 @@ devstat_new_entry(const void *dev_name, devstat_priority priority) { struct devstat *ds; - static int once; - if (!once) { - STAILQ_INIT(&device_statq); - mtx_init(&devstat_mutex, "devstat", NULL, MTX_DEF); - once = 1; - } mtx_assert(&devstat_mutex, MA_NOTOWNED); ds = devstat_alloc(); @@ -475,10 +470,9 @@ devstat_alloc(void) static int once; mtx_assert(&devstat_mutex, MA_NOTOWNED); - if (!once) { + if (!once && atomic_cmpset_int(&once, 0, 1)) { make_dev_credf(MAKEDEV_ETERNAL, &devstat_cdevsw, 0, NULL, UID_ROOT, GID_WHEEL, 0400, DEVSTAT_DEVICE_NAME); - once = 1; } spp2 = NULL; mtx_lock(&devstat_mutex);