Date: Wed, 12 May 2010 22:55:02 +0200 From: Attilio Rao <attilio@freebsd.org> To: Jeff Roberson <jroberson@jroberson.net> Cc: current@freebsd.org, Peter Jeremy <peterjeremy@acm.org> Subject: Re: LOR: ufs vs bufwait Message-ID: <r2s3bbf2fe11005121355k43a44e22tf4c0b6849024afd1@mail.gmail.com> In-Reply-To: <alpine.BSF.2.00.1005121040390.1398@desktop> References: <20100508102005.GB1867@elmar.spoerlein.net> <20100510061057.GA93038@server.vk2pj.dyndns.org> <u2h3bbf2fe11005101353k493f3ca3v7c1216e840820c67@mail.gmail.com> <20100512141154.GF88504@acme.spoerlein.net> <alpine.BSF.2.00.1005121040390.1398@desktop>
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2010/5/12 Jeff Roberson <jroberson@jroberson.net>: > On Wed, 12 May 2010, Ulrich Sp?rlein wrote: > >> On Mon, 10.05.2010 at 22:53:32 +0200, Attilio Rao wrote: >>> >>> 2010/5/10 Peter Jeremy <peterjeremy@acm.org>: >>>> >>>> On 2010-May-08 12:20:05 +0200, Ulrich Sp?rlein <uqs@spoerlein.net> >>>> wrote: >>>>> >>>>> This LOR also is not yet listed on the LOR page, so I guess it's rath= er >>>>> new. I do use SUJ. >>>>> >>>>> lock order reversal: >>>>> 1st 0xc48388d8 ufs (ufs) @ /usr/src/sys/kern/vfs_lookup.c:502 >>>>> 2nd 0xec0fe304 bufwait (bufwait) @ >>>>> /usr/src/sys/ufs/ffs/ffs_softdep.c:11363 >>>>> 3rd 0xc49e56b8 ufs (ufs) @ /usr/src/sys/kern/vfs_subr.c:2091 >>>> >>>> I'm seeing exactly the same LOR (and subsequent deadlock) on a recent >>>> -current without SUJ. >>> >>> I think this LOR was reported since a long time. >>> The deadlock may be new and someway related to the vm_page_lock work >>> (if not SUJ). >> >> I was not able to reproduce this with a kernel prior to SUJ, a kernel >> just after SUJ went it shows this "deadlock" or infinite loop ... >> >> Now it might be that the SUJ kernel only increases the pressure so it >> happens during a systems uptime. It does not seem directly related to >> actually using SUJ on a volume, as I could reproduce it with SU only, >> too. >> >> I will try to get a hang not involving GELI and also re-do my tests when >> the volumes have neither SUJ nor SU enabled, which led to 10-20s "hangs" >> of the system IIRC. It seems SU/SUJ then only prolongs these hangs ad >> infinitum. > > I think Peter Holm also saw this once while we were testing SUJ and > reproduced ~30 second hangs with stock sources. =C2=A0At this point we ne= ed to > brainstorm ideas for adding debugging instrumentation and come up with th= e > quickest possible repro. > > It would probably be good to add some KTR tracing and log that when it > wedges. =C2=A0The core I looked at was hung in bufwait. =C2=A0Is there an= y cpu > activity or io activity when things hang? =C2=A0You'll prboably have to k= eep > iostat/vmstat in memory to find out so they don't try to fault in pages o= nce > things are hung. I think I also have some reports about deadlock on unmount -f (not specific to UFS) that seems to me still the same buffer cache async deadlock. I will forward you the traces in a separate e-mail (Peter got to reproduce it with KTR on). Attilio --=20 Peace can only be achieved by understanding - A. Einstein
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