Also mention <time.h> in sem_timedwait(3), because POSIX does,
and because the user will need it for clockid_t, struct timespec,
and TIMER_ABSTIME.
Reported by: bde
MFC after: 9 days
X-MFC with: r314179
Sponsored by: Dell EMC
This function allows the caller to specify the reference clock
and choose between absolute and relative mode. In relative mode,
the remaining time can be returned.
The API is similar to clock_nanosleep(3). Thanks to Ed Schouten
for that suggestion.
While I'm here, reduce the sleep time in the semaphore "child"
test to greatly reduce its runtime. Also add a reasonable timeout.
Reviewed by: ed (userland)
MFC after: 2 weeks
Relnotes: yes
Sponsored by: Dell EMC
Differential Revision: https://reviews.freebsd.org/D9656
