SYNTAX
void rtapi_delay(long int _nsec_);
void rtapi_delay_max();ARGUMENTS
- nsec
-
The desired delay length in nanoseconds.
BESKRIVELSE
rtapi_delay is a simple delay. It is intended only for short delays. In RTAI kernel modules it busy-waits, wasting CPU cycles. Everywhere else it sleeps: in uspace realtime modules through the realtime backend (clock_nanosleep() on POSIX and Xenomai, evl_sleep_until() on EVL, rt_sleep() on RTAI), in user processes with clock_nanosleep(). The calling thread may be scheduled out and wake up later than requested.
rtapi_delay_max returns the max delay permitted. The value is implementation dependent: 1/4 of the clock period in RTAI kernel modules (10 µs until the clock is set), 10 µs in uspace realtime modules, just under one second in user processes. Any call to rtapi_delay requesting a delay longer than the max will delay for the max time only.
rtapi_delay_max should be called before using rtapi_delay to make sure the required delays can be achieved. The actual resolution of the delay may be as good as one nano-second, or as bad as a several microseconds.
SANNTIDSBETRAKTNINGER
May be called from init/cleanup code.
Calling rtapi_delay from a realtime task, while possible, is very strongly discouraged. Everywhere except in RTAI kernel modules it sleeps and may wake up considerably later than requested, which throws off the realtime thread’s timing.
RETURVERDI
rtapi_delay_max returns the maximum delay permitted.