delayed process exit

Recent versions of CURRENT running on a uniprocessor Celeron _at_ 1800 have
started (some time during this week) to behave a bit strangely.  I last
updated my home workstation yesterday (Thursday 21 Oct) and the bug is
still there.

Some times, in a seemingly unpredictable manner, exiting processes take
a lot of time to finish.  I'm seeing this almost every time I exit
Emacs, because bash takes a long time to show me a shell prompt.

I've tried ktrace on the processes that take a long time to exit, but
the timestamp of the last call to exit() is not significantly larger
than the rest of the trace output.  Whatever causes this happens after
exit() has been called.

Is anyone else seeing something similar?
Any ideas why this might be happening?

If you need more information about the setup of the machine (for
instance, the kernel config file, since it's running a slightly
modified version of GENERIC), I'll have to post a followup when I get
home in 5-6 hours.

In the meantime, if anyone has some idea that might help me track
this, it's also welcome.

- Giorgos