From owner-freebsd-current@FreeBSD.ORG Fri Dec 5 21:09:06 2008 Return-Path: Delivered-To: freebsd-current@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id D7A27106564A for ; Fri, 5 Dec 2008 21:09:06 +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 7DAF18FC1A for ; Fri, 5 Dec 2008 21:09:06 +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 mB5L90oc045107; Fri, 5 Dec 2008 16:09:00 -0500 (EST) (envelope-from jhb@freebsd.org) From: John Baldwin To: "Paul B. Mahol" Date: Fri, 5 Dec 2008 16:08:49 -0500 User-Agent: KMail/1.9.7 References: <200811191510.53793.jhb@FreeBSD.org> <200812051206.01927.jhb@freebsd.org> <3a142e750812051256v1c0c4f3eke2f953b907a4653@mail.gmail.com> In-Reply-To: <3a142e750812051256v1c0c4f3eke2f953b907a4653@mail.gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200812051608.50120.jhb@freebsd.org> X-Greylist: Sender succeeded SMTP AUTH authentication, not delayed by milter-greylist-2.0.2 (server.baldwin.cx [IPv6:::1]); Fri, 05 Dec 2008 16:09:00 -0500 (EST) X-Virus-Scanned: ClamAV 0.93.1/8728/Fri Dec 5 10:44:27 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: freebsd-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: Fri, 05 Dec 2008 21:09:06 -0000 On Friday 05 December 2008 03:56:31 pm Paul B. Mahol wrote: > On 12/5/08, John Baldwin wrote: > > On Thursday 20 November 2008 05:47:28 pm John Baldwin wrote: > >> 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). > > > > So this should now be fixed with this commit. If you could verify that > > iconv > > works ok with the latest kern_module.c I would appreciate it. > > > > Author: jhb > > Date: Fri Dec 5 16:47:30 2008 > > New Revision: 185642 > > URL: http://svn.freebsd.org/changeset/base/185642 > > > > Log: > > When the SYSINIT() to load a module invokes the MOD_LOAD event > > successfully, > > move that module to the head of the associated linker file's list of > > modules. > > The end result is that once all the modules are loaded, they are sorted in > > the reverse of their load order. This causes the kernel linker to invoke > > the MOD_QUIESCE and MOD_UNLOAD events in the reverse of the order that > > MOD_LOAD was invoked. This means that the ordering of MOD_LOAD events > > that > > is set by the SI_* paramters to DECLARE_MODULE() are now honored in the > > same > > order they would be for SYSUNINIT() for the MOD_QUIESCE and MOD_UNLOAD > > events. > > > > MFC after: 1 month > > > > -- > > John Baldwin > > > > Yes it works, I tried hard multiple times kldload/kldunload > {libiconv,cd9660,cd9660_iconv in various order} to livelock/panic it, > but without success. > > FYI following LORs happened: > > lock order reversal: > 1st 0xc4322ce8 isofs (isofs) @ /usr/src/sys/kern/vfs_lookup.c:442 > 2nd 0xd7d8d740 bufwait (bufwait) @ /usr/src/sys/kern/vfs_bio.c:2443 > 3rd 0xc4322bdc isofs (isofs) @ > /usr/src/sys/modules/cd9660/../../fs/cd9660/cd9660_vfsops.c:694 This LOR should be addressed in the latest cd9660 locking patches. -- John Baldwin