[exim] Exim processes hanging in 'futex' system call

Hello list,

recently we had a problem with an exim installation at one of our
customers. Remote connections would just time out, while local
connections still worked. We didn't have much time to investigate,
restarted the service and could connect again.

Afterwards we noticed some old exim processes (children of init) just
sitting there for days.

# strace -p 28830
Process 28830 attached - interrupt to quit
futex(0x7f4868a339e0, FUTEX_WAIT_PRIVATE, 2, NULL^C <unfinished ...>
Process 28830 detached

We killed them and restarted the service again, but they 'came back'.
Currently we accumulate 1 or 2 of these processes per day. Yesterday we
had to restart the service again (same symptoms as for the first
restart). System is debian lenny 64 bit.

Has anyone else seen this before?

--
Matthias Förste