spin lock sched lock held by 0xffffff007b712250 for > 5 seconds

After todays kernelbuild the system seem to be a lot better...
It can take quite some buildworld abuse, but still:

spin lock sched lock held by 0xffffff007b712250 for > 5 seconds
panic: spin lock held too long
cpuid = 1;
KDB: enter: panic



But I'm not shure what I could/should do now, since the KDB introduction.
Normally I'd expect to see:
db>

But there no way to get any response.

--WjW