From owner-freebsd-current@FreeBSD.ORG Wed Mar 4 18:52:39 2009 Return-Path: Delivered-To: current@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id D501C1065688 for ; Wed, 4 Mar 2009 18:52:39 +0000 (UTC) (envelope-from jhb@freebsd.org) Received: from cyrus.watson.org (cyrus.watson.org [65.122.17.42]) by mx1.freebsd.org (Postfix) with ESMTP id 951128FC13 for ; Wed, 4 Mar 2009 18:52:39 +0000 (UTC) (envelope-from jhb@freebsd.org) Received: from server.baldwin.cx (pool-98-109-39-197.nwrknj.fios.verizon.net [98.109.39.197]) by cyrus.watson.org (Postfix) with ESMTPSA id 2625E46B52; Wed, 4 Mar 2009 13:52:39 -0500 (EST) Received: from localhost (john@localhost [127.0.0.1]) (authenticated bits=0) by server.baldwin.cx (8.14.3/8.14.3) with ESMTP id n24IqXi2097243; Wed, 4 Mar 2009 13:52:33 -0500 (EST) (envelope-from jhb@freebsd.org) From: John Baldwin To: barney_cordoba@yahoo.com Date: Wed, 4 Mar 2009 13:52:27 -0500 User-Agent: KMail/1.9.7 References: <440962.16587.qm@web63902.mail.re1.yahoo.com> In-Reply-To: <440962.16587.qm@web63902.mail.re1.yahoo.com> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200903041352.27709.jhb@freebsd.org> X-Greylist: Sender succeeded SMTP AUTH authentication, not delayed by milter-greylist-2.0.2 (server.baldwin.cx [127.0.0.1]); Wed, 04 Mar 2009 13:52:33 -0500 (EST) X-Virus-Scanned: ClamAV 0.94.2/9067/Wed Mar 4 05:06:09 2009 on server.baldwin.cx X-Virus-Status: Clean X-Spam-Status: No, score=-4.4 required=4.2 tests=ALL_TRUSTED,AWL,BAYES_00 autolearn=ham version=3.1.3 X-Spam-Checker-Version: SpamAssassin 3.1.3 (2006-06-01) on server.baldwin.cx Cc: current@freebsd.org Subject: Re: MTX Lock implementation question X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 04 Mar 2009 18:52:40 -0000 On Wednesday 04 March 2009 1:45:43 pm Barney Cordoba wrote: > > --- On Wed, 3/4/09, John Baldwin wrote: > > > From: John Baldwin > > Subject: Re: MTX Lock implementation question > > To: barney_cordoba@yahoo.com > > Cc: current@freebsd.org > > Date: Wednesday, March 4, 2009, 1:05 PM > > On Wednesday 04 March 2009 12:34:40 pm Barney Cordoba wrote: > > > > > > --- On Wed, 3/4/09, John Baldwin > > wrote: > > > > > > > From: John Baldwin > > > > Subject: Re: MTX Lock implementation question > > > > To: freebsd-current@freebsd.org, > > barney_cordoba@yahoo.com > > > > Cc: current@freebsd.org > > > > Date: Wednesday, March 4, 2009, 10:13 AM > > > > On Wednesday 04 March 2009 7:54:32 am Barney > > Cordoba wrote: > > > > > > > > > > Suppose the following: > > > > > > > > > > Module foo.c > > > > > > > > > > foo_getlock(sc) > > > > > { > > > > > FOO_LOCK(sc); > > > > > } > > > > > foo_unlock(sc) > > > > > { > > > > > FOO_UNLOCK(sc); > > > > > } > > > > > foo_dosomething(sc) > > > > > { > > > > > MTX_LOCK_ASSERT(sc); > > > > > foo_dooit(); > > > > > } > > > > > > > > > > Module bar.c > > > > > > > > > > bar_dofoo() > > > > > { > > > > > foo_getlock(sc); > > > > > foo_dosomething(sc); > > > > > foo_unlock(sc); > > > > > } > > > > > > > > This works fine. > > > > > > > > > Is this something that shouldn't work? I > > need to > > > > access functions > > > > > that require locks in a different module, > > but this > > > > code barfs on > > > > > ASSERT with witness enabled. Is this a > > deflugalty in > > > > WITNESS, or do > > > > > I need to create functions within foo that > > do the > > > > locking? Its been > > > > > working ok for awhile (its not a high volume > > function) > > > > but when I > > > > > fired up witness to debug something else I > > encountered > > > > witness panics. > > > > > > > > You probably have a real bug that WITNESS is > > warning about > > > > however. > > > > > > > > -- > > > > John Baldwin > > > > > > It seems that theres a problem when the mutex is > > initialized with a type > > > of NULL. Changing it to a non-null string eliminated > > the issue. I'm > > > running a 7.0 base system. > > > > Hmm, mutexes are required to be named. The > > "type" argument is optional, but > > the name is not. So you can't do: > > > > mtx_init(&m, NULL, NULL, MTX_DEF); > > > > > > You can, however do: > > > > mtx_init(&m, "foo", NULL, MTX_DEF); > > > There seems to be an issue when the type is set to NULL. I got > panics in strcpy and strlen functions when displaying warning > traces that cleared up when the type was set to a string. There are literally thousands of mutexes in the kernel with a NULL type. Are you only seeing panics after doing a kldlunload? Alternatively, if you are not destroying your mutexes using mtx_destroy() and you are using dynamically created strings for your mutex name that could cause what you see. -- John Baldwin