The function int pthread_mutexattr_setprioceiling(pthread_mutexattr_t *attr, int prioceiling); sets the priority ceiling attribute of a mutexattr object (which was prev. created by the function pthread_mutexattr_init()). 'Prioceiling' contains the priority ceiling of initialized mutexes. The values of 'prioceiling' are within the maximum range of priorites defined by SCHED_FIFO. Upon success, it returns 0. It MAY fail if: [EINVAL] - 'attr' or 'prioceiling' is invalid. [EPERM] - The caller doesn't have the privilege to perform the operation.