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
