This is when I hit ^\ to core a stuck program:

panic: exit_lwps: lwp_wait1 failed with error 11

Begin traceback...
exit_lwps(...) at netbsd:exit_lwps+0x270
exit1(...) at netbsd:exit1+0x140
sigexit(...) at netbsd:sigexit+0xe3
postsig(...) at netbsd:postsig+0xa2
syscall_plain(...) at netbsd:syscall_plain+0x125
End traceback...
syncing disks...  (hangs)

--Michael