Listing 16: (a) RTLinux FIFO latency; (b) RTLinux FIFO latency output.

(a)
Thread
   rtl_no_interrupts(flags);
   clock_gettime(CLOCK_REALTIME, &start);
   rtl_write(fd, buf, 0);
   rtl_restore_interrupts(flags);
Handler
   clock_gettime(CLOCK_REALTIME, &end);

(b)
Testing handler latency...
NULL rtl_write() handler took 8.1 us
NULL rtl_write() handler took 2.9 us
NULL rtl_write() handler took 2.9 us