Date: Mon, 29 Jun 2009 20:16:52 +0400 From: pluknet <pluknet@gmail.com> To: Kostik Belousov <kostikbel@gmail.com> Cc: Attilio Rao <attilio@freebsd.org>, freebsd-stable <freebsd-stable@freebsd.org> Subject: Re: [nfs] process locks in "bo_wwait" on 6.4 Message-ID: <a31046fc0906290916j3a92a5d2t54f697936627f1cc@mail.gmail.com> In-Reply-To: <20090629132116.GZ2884@deviant.kiev.zoral.com.ua> References: <a31046fc0906260944h68eed26bs256dcad1f29871ff@mail.gmail.com> <a31046fc0906260951i66c239e1yfac9048d69784209@mail.gmail.com> <a31046fc0906290329p3e9cff1dwa89c8bb88736fed7@mail.gmail.com> <3bbf2fe10906290458v3d57441ar44c4ed8f36c957f@mail.gmail.com> <a31046fc0906290555ib9abf4fy90502eb01e2ef8d3@mail.gmail.com> <3bbf2fe10906290611j683a0ddawbd524e406e832d54@mail.gmail.com> <a31046fc0906290618r31e5bfb0h9e267fadef53408a@mail.gmail.com> <20090629132116.GZ2884@deviant.kiev.zoral.com.ua>
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2009/6/29 Kostik Belousov <kostikbel@gmail.com>: > On Mon, Jun 29, 2009 at 05:18:03PM +0400, pluknet wrote: >> 2009/6/29 Attilio Rao <attilio@freebsd.org>: >> > 2009/6/29 pluknet <pluknet@gmail.com>: >> >> 2009/6/29 Attilio Rao <attilio@freebsd.org>: >> >>> 2009/6/29 pluknet <pluknet@gmail.com>: >> >>>> 2009/6/26 pluknet <pluknet@gmail.com>: >> >>>>> 2009/6/26 pluknet <pluknet@gmail.com>: >> >>>>>> Hello. >> >>>>>> >> >>>>>> While building a module on nfs mounted /usr/src >> >>>>>> I got an unkillable process waiting forever in bo_wwait. >> >>>>> >> >>>>> Small note: iface on NFS server has mtu changed from 1500 to 1450. >> >>>>> Can this be a source of the problem? >> >>>> >> >>>> This is 100% reproducible. Lock in the same place. Any hints? >> >>> >> >>> Can you also show the value of ps? >> >>> A precise map of what processes are doing would give an help. >> >>> Also would be useful to printout traces for other threads and not only >> >>> the stucked one. >> >>> >> >> >> >> >From another run: >> > >> > I'm unable to see who would be locking the buffer object in question. >> > Do you have INVARIANT_SUPPORT/INVARIANTS on? >> >> Yes, I do both. >> >> > What revision of /usr/src/sys/kern/vfs_bio.c are you running with? >> > >> >> As of 6.4-R: CVS rev 1.491.2.12.4.1 / SVN rev 183531. > > It seems that your changes of MTU cause nfs requests to never reach > network. bo_wwait is the state where thread waits for all outstanding > i/o on bufobj to drain. > It appears that you are right. I found in tcpdump that nfs client tries to send UDP packets sized in 1500 bytes. 19:40:13.937085 IP (tos 0x0, ttl 64, id 4658, offset 0, flags [+], proto: UDP (17), length: 1500) client.1662412076 > server.nfs: 1472 write fh 1145,216955/1372174 1779 (1779) bytes @ 0 <unstable> While here I reverted mtu on NFS server back to 1500, then after some seconds "locked up" NFS client box continued to build a module as there were no any locking problems at all. So I understand this as defined behavior. -- wbr, pluknet
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