James Robinson <jlrobins(at)socialserve(dot)com> writes:
> As fate would have it, the vacuumdb frontend and backend which were
> initially afflicted are still in existence:
OK, so pid 19244 isn't blocked on any lmgr lock; else we'd see an entry
with granted = f for it in pg_locks. It could be blocked on a lower
level lock though. Can you attach to that PID with gdb and get a stack
trace? Something like (as postgres user)
gdb /path/to/postgres-executable 19244
gdb> bt
gdb> quit
ok to detach? yes
regards, tom lane