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The pthread_mutexattr_getprioceiling() and pthread_mutexattr_setprioceiling() functions, respectively, get
and set the priority ceiling attribute of a mutex attribute object pointed
to by attr, which was previously created by the pthread_mutexattr_init() function.
The prioceiling attribute contains the
priority ceiling of initialized mutexes. The values of prioceiling must be within the maximum range of priorities defined by
SCHED_FIFO.
The prioceiling attribute defines the priority
ceiling of initialized mutexes, which is the minimum priority level at which
the critical section guarded by the mutex is executed. In order to avoid
priority inversion, the priority ceiling of the mutex must be set to a priority
higher than or equal to the highest priority of all the threads that may
lock that mutex. The values of prioceiling must
be within the maximum range of priorities defined under the SCHED_FIFO scheduling policy.
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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