panic during 'cvs -R -d /home/dcvs/ checkout src'

Matthew Dillon dillon at
Mon Jan 26 20:36:53 PST 2004

:So I just cvsup'ed twenty minutes ago to grab Rob's RCNG changes, that
:went fine.  Then I did the next step, the CVS checkout, and my machine
:panicked.  Like so:
:  catbus# cvs -R -d /home/dcvs/ checkout src
:  cvs: WARNING: Read-only repository access mode selected via 'cvs -R'.
:  Using this option to access a repository which some users write to
:  may cause intermittent sandbox corruption.
:  U src/bin/csh/config.h
:  U src/bin/csh/host.defs
:  M src/bin/ln/ln.1
:  U src/contrib/ntp/ntpd/ntp_loopfilter.c
:  panic: lockmgr: non-zero exclusive count
:  Debugger("panic")
:  Stopped at      Debugger+0x34:  movb    $0,in_Debugger.342
:  db>
:The machine's still sitting at that prompt, and I can leave it there
:pretty much indefinately, so if anyone can make suggestions on how to
:get useful information out of DDB, please do!  Meanwhile I'm going to
:read up on chapter 10 of the FreeBSD Developer's Handbook because it's
:been quite a while since I've used a debugger in any seriousness...

    Ok, first thing to do is 'show regi'  (show registers).  Pick the stack
    pointer and write it down.

    Then do a 'trace'.  If the trace doesn't look good, try tracing with
    the stack pointer plus an offset of 4 and of 8.  You should get a good
    trace.   e.g. if the stack pointer were 0xdaaaaa08  you could try
    'trace 0xdaaaaa0c' and 'trace 0xdaaaaa10'.

    If you can get a crash dump that would be good to, typing 'panic' and
    hitting return once or twice will get you there. but if you haven't
    already set it up there nothing you can do about it now and that will
    reboot the machine.

    I've seen this type of crash before, but have not yet been able to track
    it down.

					Matthew Dillon 
					<dillon at xxxxxxxxxxxxx>

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