Blocking cond_signal?

Hey all-

I've been lurking this list (via the archives) for a while now for help
writing threaded programs. You've been a really good resource, but I've
run into a snag that I can't quite figure out.

In my application, I need a thread to wait on another thread to send a
cond_signal. Easy enough, but if the second thread hasn't reached the
cond_wait by the time the cond_signal appears, then the signal is
discarded and the cond_wait will end up blocking forever.

The POD reads: "By always locking before signaling, you can (with care),
avoid signaling before another thread has entered cond_wait()" But every
scheme I've attempted ensure this has been racy and fragile.

Could someone please shed light on this?

Thanks in advance-
Andrew