From owner-freebsd-current@FreeBSD.ORG Thu Nov 20 22:48:26 2008 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 969F41065672 for ; Thu, 20 Nov 2008 22:48:26 +0000 (UTC) (envelope-from jhb@freebsd.org) Received: from server.baldwin.cx (bigknife-pt.tunnel.tserv9.chi1.ipv6.he.net [IPv6:2001:470:1f10:75::2]) by mx1.freebsd.org (Postfix) with ESMTP id 153858FC22 for ; Thu, 20 Nov 2008 22:48:25 +0000 (UTC) (envelope-from jhb@freebsd.org) Received: from localhost.corp.yahoo.com (john@localhost [IPv6:::1]) (authenticated bits=0) by server.baldwin.cx (8.14.3/8.14.3) with ESMTP id mAKMmDYM069308; Thu, 20 Nov 2008 17:48:20 -0500 (EST) (envelope-from jhb@freebsd.org) From: John Baldwin To: "Paul B. Mahol" Date: Thu, 20 Nov 2008 17:47:28 -0500 User-Agent: KMail/1.9.7 References: <200811191510.53793.jhb@FreeBSD.org> <3a142e750811201330p3084255em390d94b352dee532@mail.gmail.com> In-Reply-To: <3a142e750811201330p3084255em390d94b352dee532@mail.gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200811201747.28540.jhb@freebsd.org> X-Greylist: Sender succeeded SMTP AUTH authentication, not delayed by milter-greylist-2.0.2 (server.baldwin.cx [IPv6:::1]); Thu, 20 Nov 2008 17:48:20 -0500 (EST) X-Virus-Scanned: ClamAV 0.93.1/8654/Thu Nov 20 14:51:00 2008 on server.baldwin.cx X-Virus-Status: Clean X-Spam-Status: No, score=-2.6 required=4.2 tests=AWL,BAYES_00,NO_RELAYS 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: [PATCH] MPSAFE/LOOKUP_SHARED cd9660 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: Thu, 20 Nov 2008 22:48:26 -0000 On Thursday 20 November 2008 04:30:57 pm Paul B. Mahol wrote: > On 11/19/08, John Baldwin wrote: > > This is a relatively simple patch to mark cd9660 MPSAFE and enable shared > > lookups. The changes to cd9660_lookup() mirror similar changes to > > ufs_lookup() to use static variables for local data rather than abusing > > i-node members of the parent directory. I've done some light testing of > > this, but not super-strenuous. This patch also includes simple locking for > > the iconv support in the kernel. That locking uses an sx lock to serialize > > open and close of translator tables and the associated refcount. Actual > > conversions do not need any locks, however as the mount holds a reference on > > the table. > > > > http://www.FreeBSD.org/~jhb/patches/cd9660_mpsafe.patch > > > > With this patch I'm unable to kldunload libiconv.ko once it is loaded. > And trying to kldunload libiconv.ko will make any next kldload/kldstat/kldunload > to fail waiting forever(livelock). > > Regression were not encountered while only cd9660.ko were kldloaded. So this is actually due to a bug in the module code. If you have two modules like this: DECLARE_MODULE(foo, SI_SUB_DRIVERS, SI_ORDER_FIRST); DECLARE_MODULE(bar, SI_SUB_DRIVERS, SI_ORDER_SECOND); The SI_* constants ensure that foo's module handler is called before bar's module handler for MOD_LOAD. However, we don't enforce a reverse order (bar then foo) for MOD_UNLOAD. In fact, the order of MOD_UNLOAD events is random and has no relation to the SI_* constants. :( What is happening here is that one of the 'bar' modules in libiconv.ko is getting unloaded after 'foo' gets unloaded and using a destroyed lock (you get a panic if you run with INVARIANTS). -- John Baldwin