core-dumping over NFS
rwatson at FreeBSD.org
Mon Jan 12 12:42:59 PST 2004
On Mon, 12 Jan 2004, Mikhail Teterin wrote:
> I've observed the following bad behaviour of -current mostly related to
> dumping core of a buggy program over the NFS.
Sounds unfortunate. A quick starting question: Does the behavior change
at all if the core file does or doesn't already exist? Another question:
this is a FreeBSD binary, or is it emulated? Could you send the output of
running 'file' on the binary?
> . 5.2-CURRENT (Dec 14) client, Solaris-8 server:
> created core file is empty (zero sized).
Not sure how much RPC fun you want to have, but if you could do a tcpdump
of the RPC exchange here, would be very helpful. Run ethereal on the
result, and look for creation/lookup of the file. It would be interesting
to see if one of the RPCs is failing. In particular, I notice that the
coredump code calls VOP_SETATTR() to truncate the file without checking
the return value.
> . 5.2-CURRENT (Dec 14) server, RedHat-9 client:
> core is created properly, but sometimes the server goes
> into a frenzy with the sys-component (bufdaemon) taking
> up the entire 100% of the CPU-time (P4 at 2GHz); it only
> writes @4Mb/s (~14% of the disk's bandwidth) and the
> only cure is to restart the /etc/rc.d/nfsd; trying to,
> for example, switch from X11 to a textual console, when
> this is happening reliably hangs the machine.
Er. Ouch. Can you confirm if there's an on-going series of RPCs from the
client driving the I/O, or if it's just things going nuts on the server?
Also, what block size is the RedHat client using by default? Could you
set up a serial console -- if so, do you get any interesting messages?
> . 5.2-CURRENT (Dec 14) server, 5.2-RC2 (Jan 10) client:
> dumps happen normally with rw-mounts, but mounting the
> FS read-only (so as to prevent core-dumps) leads to a
> panic on the client...
> The mounts are regular and default (v3?), except for the ``intr'' flag.
> No rpc.lock or anything...
Could you provide the panic message and stack trace?
Robert N M Watson FreeBSD Core Team, TrustedBSD Projects
robert at fledge.watson.org Senior Research Scientist, McAfee Research
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