nanospin_ns()

Busy-wait without blocking for a period of time

Synopsis:

#include <time.h>

int nanospin_ns( unsigned long nsec );

Arguments:

nsec

The number of nanoseconds that you want to busy-wait for.

Library:

libc

Use the -l c option to qcc to link against this library. This library is usually included automatically.

Description:

The nanospin_ns() function busy-waits for the number of nanoseconds specified in nsec, without blocking the calling thread.

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The nanospin*() functions are designed for use with hardware that requires short time delays between accesses. You should use them to delay only for times less than a few milliseconds. For longer delays, use the POSIX timer_*() functions.

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The first time you call nanospin_ns(), the C library invokes nanospin_calibrate() with an argument of 0 (interrupts enabled), if you haven't invoked it directly first.

Returns:

EOK

Success.

E2BIG

The delay specified by nsec is greater than 500 milliseconds.

---

A delay of more than a few milliseconds might not work on some processors. For longer delays, use the POSIX timer_*() functions.

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EINTR

A too-high rate of interrupts occurred during the calibration routine.

ENOSYS

This system's startup-* program didn't initialize the timing information necessary to use nanospin_ns().

Classification:

QNX Neutrino

Caveats:

You should use busy-waiting only when absolutely necessary for accessing hardware.

It isn't safe to call this function in an interrupt handler if nanospin_calibrate() hasn't been called yet.

See also:

nanosleep(), nanospin(), nanospin_calibrate(), nanospin_count(), nanospin_ns_to_count(), sched_yield(), sleep(), timer_create()