cc –mt [ flag... ] file... [ library... ] #include <pthread.h> int pthread_mutexattr_getprioceiling( const pthread_mutexattr_t *restrict attr, int *restrict prioceiling);
int pthread_mutexattr_setprioceiling(pthread_mutexattr_t *attr, int prioceiling);
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 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 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(3C).
Upon successful completion, the pthread_mutexattr_getprioceiling() and pthread_mutexattr_setprioceiling() functions return 0. Otherwise, an error number is returned to indicate the error.
The pthread_mutexattr_setprioceiling() function will fail if:
The value specified by attr is NULL or prioceiling is invalid.
The pthread_mutexattr_getprioceiling() and pthread_mutexattr_setprioceiling() functions may fail if:
The value specified by attr or prioceiling is invalid.
The caller does not have the privilege to perform the operation.
See attributes(5) for descriptions of the following attributes: