The pthread_mutex_getprioceiling() function shall return the current
priority ceiling of the mutex.
The pthread_mutex_setprioceiling() function shall either lock the mutex
if it is unlocked, or block until it can successfully lock the mutex, then it
shall change the mutex's priority ceiling and release the mutex. When the
change is successful, the previous value of the priority ceiling shall be
returned in old_ceiling. The process of locking the mutex need not
adhere to the priority protect protocol.
If the pthread_mutex_setprioceiling() function fails, the mutex priority
ceiling shall not be changed.
Portions of this text are reprinted and reproduced in electronic form from IEEE
Std 1003.1, 2003 Edition, Standard for Information Technology -- Portable
Operating System Interface (POSIX), The Open Group Base Specifications Issue
6, Copyright (C) 2001-2003 by the Institute of Electrical and Electronics
Engineers, Inc and The Open Group. In the event of any discrepancy between
this version and the original IEEE and The Open Group Standard, the original
IEEE and The Open Group Standard is the referee document. The original
Standard can be obtained online at http://www.opengroup.org/unix/online.html