On Sun, 12 Mar 2017, gwes wrote:
> I'm trying to debug the following panic.
> I can't get a crash dump.
> At the DDB prompt, either "boot sync" or "boot dump"
> the system prints "Syncing disks: 2" and nothing more.
So you asked it to sync the disks and that was unable complete: if it did
it would have said "done". Why couldn't it complete? Hard to say;
perhaps one of the other CPUs was holding a lock when ddb stopped it, or
maybe you have a filesystem mounted from the involved USB device.
(What's the '2'? It's a count of buffers that couldn't be written out;
the kernel normally pauses a moment to give disks time to do their stuff
and thus tries flushing everything again, leading to a string of numbers
with pauses between them, ala "12 12 12 8 7 6 3 1 done". That behavior
goes back a *long* ways; I recall watching that count down on SunOS 4.1
systems back in the early '90s.)
Instead of doing "boot dump", you can try "boot crash" which skips the
file system sync before dumping the kernel crash. If you can reliably
reproduce the problem then I would suggest remounting as many filesytem
read-only as possible before triggering the panic to minimize the possible
filesystem damage.
Philip Guenther
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