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The pthread_mutex_getprioceiling() function returns
the current priority ceiling of the mutex.
The pthread_mutex_setprioceiling() function either
locks the mutex if it is unlocked, or blocks until it can successfully lock
the mutex, then it changes the mutex's priority ceiling and releases the
mutex. When the change is successful, the previous value of the priority
ceiling is 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 is not changed.
The ceiling value should be drawn from the range of priorities for
the SCHED_FIFO policy. When a thread acquires such a
mutex, the policy of the thread at mutex acquisition should match that from
which the ceiling value was derived (SCHED_FIFO, in this
case). If a thread changes its scheduling policy while holding a ceiling
mutex, the behavior of pthread_mutex_lock() and pthread_mutex_unlock() on this mutex is undefined. See pthread_mutex_lock(3THR).
The ceiling value should not be treated as a persistent value resident
in a pthread_mutex_t that is valid across upgrades of
Solaris. The semantics of the actual ceiling value are determined by the
existing priority range for the SCHED_FIFO policy, as
returned by the sched_get_priority_min() and sched_get_priority_max() functions (see sched_get_priority_min(3RT)) when called on the version of Solaris on which the
ceiling value is being utilized.
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