pthread_mutexattr_setprotocol
int pthread_mutexattr_setprotocol(pthread_mutexattr_t*,
PTHREAD_REQUIRE(pthread_mutexattr_setprotocol(&attr5,
PTHREAD_REQUIRE(pthread_mutexattr_setprotocol(&mattr, target));
PTHREAD_REQUIRE(pthread_mutexattr_setprotocol(&mattr, target));