spin sleep

foo.c

uint64_t
sl_getnsecs()
{
	struct timespec ts;
	(void) clock_gettime(CLOCK_MONOTONIC, &ts);
	return (((uint64_t)ts.tv_sec * 1000000000L) + ts.tv_nsec);
}

/*
 * Spin until approximately ns nanoseconds have passed. The ns value
 * must be at least 1 nanosecond.
 */
static void
sl_spin(uint64_t ns)
{
	uint64_t passed = 0;
	uint64_t start = sl_getnsecs();
	assert(ns > 0);

	while (passed < ns)
		passed = (sl_getnsecs()) - start;
}