Breaking out of pthread_mutex_lock

[Darren Hart <dvhltc@us.ibm.com>]

I find I need to be able to break out of the blocked state while waiting
to acquire a pthread_mutex.  I'm using PI mutexes and want to continue
to do so.  As I understand it, I can't use a signal to break out of the
lock as the man pages states:

"If a signal is delivered to a thread waiting for a mutex,  upon  return
from  the  signal handler the thread shall resume waiting for the mutex
as if it was not interrupted."

and that pthread_mutex_lock will not return EINTR.  I had considered
using cond variables, but I don't think they will provide the same PI
behavior (since the threads are not blocked on the mutex while awaiting
the pthread_cond_signal - right?).

I'm sure I'm not the first to want to do this, does anyone know of a
common best practice for accomplishing such a thing?

-- 
Darren Hart
Real-Time Linux Team
IBM Linux Technology Center