clock_lock       1181 src/dps8/dps8_scu.c static pthread_mutex_t clock_lock = PTHREAD_MUTEX_INITIALIZER;
clock_lock       1269 src/dps8/dps8_scu.c     pthread_mutex_lock (& clock_lock);
clock_lock       1420 src/dps8/dps8_scu.c     pthread_mutex_unlock (& clock_lock);