clock_lock       1162 src/dps8/dps8_scu.c static pthread_mutex_t clock_lock = PTHREAD_MUTEX_INITIALIZER;
clock_lock       1169 src/dps8/dps8_scu.c     pthread_mutex_lock (& clock_lock);
clock_lock       1301 src/dps8/dps8_scu.c     pthread_mutex_unlock (& clock_lock);