Date: Tue, 07 Mar 2017 20:45:40 +0100 From: Harry Schmalzbauer <freebsd@omnilan.de> To: Rick Macklem <rmacklem@uoguelph.ca> Cc: Konstantin Belousov <kostikbel@gmail.com>, FreeBSD Stable <freebsd-stable@freebsd.org>, Mark Johnston <markj@freebsd.org>, "kib@FreeBSD.org" <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] Message-ID: <58BF0DE4.1020300@omnilan.de> In-Reply-To: <58BEFF83.9010906@omnilan.de> References: <57A79E24.8000100@omnilan.de> <YQBPR01MB0401201977AEA8A803F27B23DD1A0@YQBPR01MB0401.CANPRD01.PROD.OUTLOOK.COM> <57A83C78.1070403@omnilan.de> <20160809060213.GA67664@raichu> <57A9A6C0.9060609@omnilan.de> <YTOPR01MB0412B2A08F1A3C1A3B2EB160DD1E0@YTOPR01MB0412.CANPRD01.PROD.OUTLOOK.COM>, <20160812123950.GO83214@kib.kiev.ua> <YTXPR01MB018919BE87B12E458144E218DD140@YTXPR01MB0189.CANPRD01.PROD.OUTLOOK.COM>, <57B8793E.4070004@omnilan.de> <YTXPR01MB018948D19A0A9BB5FAC3D5BADDE60@YTXPR01MB0189.CANPRD01.PROD.OUTLOOK.COM> <58BEAAAC.4090303@omnilan.de> <58BEFF83.9010906@omnilan.de>
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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
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