From owner-freebsd-stable@freebsd.org Tue Mar 7 19:45:43 2017 Return-Path: Delivered-To: freebsd-stable@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id 8F5A9D0212C for ; Tue, 7 Mar 2017 19:45:43 +0000 (UTC) (envelope-from freebsd@omnilan.de) Received: from mx0.gentlemail.de (mx0.gentlemail.de [IPv6:2a00:e10:2800::a130]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id 4094C1E02; Tue, 7 Mar 2017 19:45:43 +0000 (UTC) (envelope-from freebsd@omnilan.de) Received: from mh0.gentlemail.de (mh0.gentlemail.de [78.138.80.135]) by mx0.gentlemail.de (8.14.5/8.14.5) with ESMTP id v27Jjf1J050888; Tue, 7 Mar 2017 20:45:41 +0100 (CET) (envelope-from freebsd@omnilan.de) Received: from titan.inop.mo1.omnilan.net (titan.inop.mo1.omnilan.net [IPv6:2001:a60:f0bb:1::3:1]) (using TLSv1 with cipher ECDHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by mh0.gentlemail.de (Postfix) with ESMTPSA id ACC404F2; Tue, 7 Mar 2017 20:45:40 +0100 (CET) Message-ID: <58BF0DE4.1020300@omnilan.de> Date: Tue, 07 Mar 2017 20:45:40 +0100 From: Harry Schmalzbauer Organization: OmniLAN User-Agent: Mozilla/5.0 (X11; U; FreeBSD i386; de-DE; rv:1.9.2.8) Gecko/20100906 Lightning/1.0b2 Thunderbird/3.1.2 MIME-Version: 1.0 To: Rick Macklem CC: Konstantin Belousov , FreeBSD Stable , Mark Johnston , "kib@FreeBSD.org" Subject: Re: unionfs bugs, a partial patch and some comments [Was: Re: 1-BETA3 Panic: __lockmgr_args: downgrade a recursed lockmgr nfs @ /usr/local/share/deploy-tools/RELENG_11/src/sys/fs/unionfs/union_vnops.c:1905] References: <57A79E24.8000100@omnilan.de> <57A83C78.1070403@omnilan.de> <20160809060213.GA67664@raichu> <57A9A6C0.9060609@omnilan.de> , <20160812123950.GO83214@kib.kiev.ua> , <57B8793E.4070004@omnilan.de> <58BEAAAC.4090303@omnilan.de> <58BEFF83.9010906@omnilan.de> In-Reply-To: <58BEFF83.9010906@omnilan.de> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 8bit X-Greylist: ACL 119 matched, not delayed by milter-greylist-4.2.7 (mx0.gentlemail.de [78.138.80.130]); Tue, 07 Mar 2017 20:45:41 +0100 (CET) X-Milter: Spamilter (Reciever: mx0.gentlemail.de; Sender-ip: 78.138.80.135; Sender-helo: mh0.gentlemail.de; ) X-BeenThere: freebsd-stable@freebsd.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: Production branch of FreeBSD source code List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 07 Mar 2017 19:45:43 -0000 Bezüglich Harry Schmalzbauer's Nachricht vom 07.03.2017 19:44 (localtime): > Bezüglich Harry Schmalzbauer's Nachricht vom 07.03.2017 13:42 (localtime): > … >> Something ufs related seems to have tightened the unionfs locking >> problem in stable/11. Now the machine instantaniously panics during >> boot after mounting root with Rick's latest patch. >> >> Unfortunately I don't have SWAP available on that machine (yet), but >> maybe shit is a hint for anybody. >> >> db_trace_self_wrapper() at db_trace_self_wrapper+0x2b/frame >> 0xfffffe00982220e0 >> vpanic() at vpanic+0x186/frame 0xfffffe0098222160 >> kassert_panic() at kassert_panic+0x126/frame 0xfffffe00982221d0 >> witness_assert() at witness_assert+0x35a/frame 0xfffffe0098222230 >> __lockmgr_args() at __lockmgr_args+0x517/frame 0xfffffe00982222d0 >> vop_stdunlock() at vop_stdunlock+0x3b/frame 0xfffffe00982222f0 >> VOP_UNLOCK_APV() at VOP_UNLOCK_APV+0xe0/frame 0xfffffe0098222320 >> unionfs_unlock() at unionfs_unlock+0x112/frame 0xfffffe0098222390 >> VOP_UNLOCK_APV() at VOP_UNLOCK_APV+0xe0/frame 0xfffffe00982223c0 >> unionfs_nodeget() at unionfs_nodeget+0x3ef/frame 0xfffffe0098222470 >> unionfs_domount() at unionfs_domount+0x518/frame 0xfffffe00982226b0 >> vfs_donmount() at vfs_donmount+0xe37/frame 0xfffffe00982228f0 >> sys_nmount() at sys_nmount+0x72/frame 0xfffffe0098222930 >> amd64_syscall() at amd64_syscall+0x2f9/frame 0xfffffe0098222ab0 >> Xfast_syscall() at Xfast_syscall+0xfb/frame 0xfffffe0098222ab0 >> --- syscall (378, FreeBSD ELF64, sys_nmount), rip = 0x80086ecea, rsp = >> 0x7fffffffe318, rbp = 0x7fffffffeca0 --- > New discovery: > Rick's latest patch casues panic only with KDB. If I compile a kernel > without witenss and KDB, the machine boots fine! > Also, it's at least not so easy anymore to trigger the deadlock :-) . I > need to do more testing but until now Rick's approach seems very > promising :-) . My unionfs deadlock problem isn't really solved with Rick's latest patch, I still can reproduce it: krb5.conf and krb5.keytab are files on unionfs referenced by /etc. libexec/negotiate_kerberos_auth reads these and if I have enough helper processes handling requests, the deadlock occurs. _But_: If I move the files outside the unionfs and create a symlink, I cannot reproduce the deadlock anymore, which was similar easily reproducable without it or any of the other workarounds. So it looks like I have an acceptable solution for now, although it's only usable under certain conditions. Unfortunately I can't do tests with a debug kernel since the patch prevents the system with the debug kernel from starting up. But if this was ironed out, I'd happily provide more info. Thanks, -Harry