If you are compiling under FreeBSD and see messages in the syslogs that
indicate that the ntpd process is trying to use unavailable sched_
calls, it means you are running a kernel that does not have the POSIX
scheduling calls enabled.

You have two choices:

- Ignore the messages

- Generate a new kernel, where the kernel configuration file contains
  the lines:

  options		"P1003_1B"
  options		"_KPOSIX_PRIORITY_SCHEDULING"
  options		"_KPOSIX_VERSION=199309L"