From owner-freebsd-current@FreeBSD.ORG Thu Feb 7 10:44:05 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 322E616A418; Thu, 7 Feb 2008 10:44:05 +0000 (UTC) (envelope-from kostikbel@gmail.com) Received: from relay02.kiev.sovam.com (relay02.kiev.sovam.com [62.64.120.197]) by mx1.freebsd.org (Postfix) with ESMTP id AF06013C44B; Thu, 7 Feb 2008 10:44:04 +0000 (UTC) (envelope-from kostikbel@gmail.com) Received: from [212.82.216.226] (helo=skuns.kiev.zoral.com.ua) by relay02.kiev.sovam.com with esmtps (TLSv1:AES256-SHA:256) (Exim 4.67) (envelope-from ) id 1JN4EY-0006wv-Uq; Thu, 07 Feb 2008 12:44:03 +0200 Received: from deviant.kiev.zoral.com.ua (root@deviant.kiev.zoral.com.ua [10.1.1.148]) by skuns.kiev.zoral.com.ua (8.14.1/8.14.1) with ESMTP id m17AhYSR044112 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO); Thu, 7 Feb 2008 12:43:35 +0200 (EET) (envelope-from kostikbel@gmail.com) Received: from deviant.kiev.zoral.com.ua (kostik@localhost [127.0.0.1]) by deviant.kiev.zoral.com.ua (8.14.2/8.14.2) with ESMTP id m17Ahsqp006331; Thu, 7 Feb 2008 12:43:54 +0200 (EET) (envelope-from kostikbel@gmail.com) Received: (from kostik@localhost) by deviant.kiev.zoral.com.ua (8.14.2/8.14.2/Submit) id m17AhsVW006330; Thu, 7 Feb 2008 12:43:54 +0200 (EET) (envelope-from kostikbel@gmail.com) X-Authentication-Warning: deviant.kiev.zoral.com.ua: kostik set sender to kostikbel@gmail.com using -f Date: Thu, 7 Feb 2008 12:43:54 +0200 From: Kostik Belousov To: Attilio Rao Message-ID: <20080207104354.GY57756@deviant.kiev.zoral.com.ua> References: <20080207045015.GW57756@deviant.kiev.zoral.com.ua> <3bbf2fe10802070216idd5206ey7a66c0873311e66c@mail.gmail.com> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="ovEA76cwFbc4aGSk" Content-Disposition: inline In-Reply-To: <3bbf2fe10802070216idd5206ey7a66c0873311e66c@mail.gmail.com> User-Agent: Mutt/1.4.2.3i X-Virus-Scanned: ClamAV version 0.91.2, clamav-milter version 0.91.2 on skuns.kiev.zoral.com.ua X-Virus-Status: Clean X-Scanner-Signature: 3f6c5f504711b4b2e39067d20b60c9d6 X-DrWeb-checked: yes X-SpamTest-Envelope-From: kostikbel@gmail.com X-SpamTest-Group-ID: 00000000 X-SpamTest-Header: Not Detected X-SpamTest-Info: Profiles 2189 [Feb 07 2008] X-SpamTest-Info: helo_type=3 X-SpamTest-Method: none X-SpamTest-Rate: 0 X-SpamTest-Status: Not detected X-SpamTest-Status-Extended: not_detected X-SpamTest-Version: SMTP-Filter Version 3.0.0 [0278], KAS30/Release Cc: Marcel Moolenaar , current@freebsd.org Subject: Re: Old LOR between devfs & devfsmount resurfacing? 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, 07 Feb 2008 10:44:05 -0000 --ovEA76cwFbc4aGSk Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Thu, Feb 07, 2008 at 11:16:08AM +0100, Attilio Rao wrote: > 2008/2/7, Kostik Belousov : > > On Wed, Feb 06, 2008 at 11:11:06AM -0800, Marcel Moolenaar wrote: > > > All, > > > > > > I just ran into the following LOR after upgrading my PowerPC box: > > > > > > lock order reversal: > > > 1st 0xdbee94 devfs (devfs) @ /nfs/freebsd/8.x/src/sys/kern/ > > > vfs_subr.c:2061 > > > 2nd 0xdfb014 devfsmount (devfsmount) @ /nfs/freebsd/8.x/src/sys/fs/ > > > devfs/devfs_vnops.c:201 > > > KDB: stack backtrace: > > > 0xdc0febc8: at kdb_backtrace+0x4c > > > 0xdc0febd8: at witness_checkorder+0x704 > > > 0xdc0fec28: at _sx_xlock+0x8c > > > 0xdc0fec48: at devfs_allocv+0x138 > > > 0xdc0fec88: at devfs_root+0x5c > > > 0xdc0fecb8: at set_rootvnode+0x44 > > > 0xdc0fece8: at vfs_mountroot+0x344 > > > 0xdc0fed48: at start_init+0x88 > > > 0xdc0feda8: at fork_exit+0xb4 > > > 0xdc0fedc8: at fork_trampoline+0xc > > > KDB: enter: witness_checkorder > > > [thread pid 1 tid 100001 ] > > > Stopped at 0x28ee68: addi r0, r0, 0x0 > > > > > > It seems that this is a LOR reported in 2006 and fixed > > > in 2006 as well. Do other people see this too, or should > > > I suspect my sources? > > > > > > I believe this is a false positive, caused by the way the witness works. > > Attilio recently added the witness support for the lockmgr, that caused > > this and at least two more LORs to be printed on startup. > > > > Correct lock order is devfs vnode -> devfs mount sx lock. When > > allocating new devfs vnode, see devfs_allocv(), the newly created > > vnode is locked while devfs mount lock already held (see line 250 of > > fs/devfs/devfs_vnops.c). Nonetheless, this cannot cause deadlock since > > no other thread can find the new vnode, and thus perform the other lock > > order for this vnode lock. > > > > The fix is to shut the witness in this particular case. Attilio, how to > > do this ? >=20 > Just add LK_NOWITNESS for one of the lock involved in the lockinit(). Then, we loss the useful reports of the actual LORs later, isn't it ? --ovEA76cwFbc4aGSk Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.8 (FreeBSD) iEYEARECAAYFAkeq4OkACgkQC3+MBN1Mb4hEpACcDPknBBaQ5BA4XKN/8MpsPd0p ZTEAoNtjs0j19YmKMR6t2FtIKH3MPh7o =1WDY -----END PGP SIGNATURE----- --ovEA76cwFbc4aGSk--