5.2-RELEASE: Possible bug in filesystem code?

[Daniel Papasian]

I really hate to potentially create some distress over something that may
be very difficult to repeat, but...

I was working on a 5.2-RELEASE system that had been improperly shut down,
and while the background process was checking/fixing the consistency of
the filesystem, I did a relatively disk-intensive process (installed a
port) and the system crashed in an apparent panic.

I then attempted to see if this repeated, and sure enough it did, twice.
So I built a kernel with debugging options and prepared to get a crash
dump.

To see if I hadn't tweaked inadvertently fixed the problem, I repeated the
crash with the debugging kernel but before I had set it to save core by
calling dumpon, and sure enough the system did crash again.  In
retrospect, this was a huge mistake, because the next time, when dumpon
was called and I was ready to get a crash dump, the crash did not repeat.

A case of ridiculously bad luck?  It sounds it.  When I get some time this
weekend, I'll try a bit harder to repeat the problem and get a crashdump,
but considering the nature of what I suspect the problem to be, I'm
guessing it was caused by a specific inconsistency in the filesystem from
the improper shutdown, something that has since been corrected, and would
therefore be hard to reproduce.

The filesystem used softupdates.  I'm wondering if anyone has had any
similar experiences, or if this is somehow a known problem in any way.

-Daniel Papasian