freebsd revision 290001 
1If you are compiling under FreeBSD and see messages in the syslogs that
2indicate that the ntpd process is trying to use unavailable sched_
3calls, it means you are running a kernel that does not have the POSIX
4scheduling calls enabled.
5
6You have two choices:
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8- Ignore the messages
9
10- Generate a new kernel, where the kernel configuration file contains
11  the lines:
12
13  options		"P1003_1B"
14  options		"_KPOSIX_PRIORITY_SCHEDULING"
15  options		"_KPOSIX_VERSION=199309L"
16