Is pthread_cond_signal(3) man page correct?

[Yuri]

On FreeBSD-8.1 this page says:
The pthread_cond_signal() function unblocks one thread waiting for the 
condition variable cond.

On Linux it says:
The /pthread_cond_signal/() function shall unblock at least one of the 
threads that are blocked on the specified condition variable /cond/ (if 
any threads are blocked on /cond/).

Also HP page 
(http://docs.hp.com/en/B2355-90130/pthread_cond_signal.3T.html) says: 
"If there are no threads blocked on /cond/, this function has no 
effect." And later it says: "It is possible that more than one thread 
can be unblocked due to a spurious wakeup."

This is quite confusing: in case nobody is waiting does it block or not? 
In case other threads are waiting it's really "any arbitrary number of 
threads are woken up"? Or on FreeBSD it's strictly 1? Shouldn't this be 
defined in one and only way by POSIX and all POSIX-compliant systems 
should work exactly the same.

I think man page should be expanded to give more comprehensive explanation.

Yuri