test_hrtimer.c

#include <linux/init.h>
#include <linux/module.h>
#include <linux/hrtimer.h>
#include <linux/ktime.h>
#include <linux/kthread.h>
#include <linux/delay.h>

MODULE_LICENSE("Dual BSD/GPL");
#define RX_POLL_PERIOD_MIN_US   800
#define RX_POLL_PERIOD_MAX_US   3000
#define PAUSE_MS		10
static struct hrtimer hr_timer;
static struct task_struct *t1;
static unsigned long long counter=0;

static void my_timer_forward(struct hrtimer *timer) {
         hrtimer_set_expires_range(timer,
                         ktime_add(timer->base->get_time(),
                                 ktime_set(0, RX_POLL_PERIOD_MIN_US *
                                         NSEC_PER_USEC)),
                         ktime_set(0, (RX_POLL_PERIOD_MAX_US -
                                         RX_POLL_PERIOD_MIN_US) *
                                 NSEC_PER_USEC));
}

enum hrtimer_restart my_hrtimer_callback( struct hrtimer *timer ) {


	udelay(50);

	printk(KERN_ALERT "!");
	my_timer_forward(timer);
	counter++;
	return HRTIMER_RESTART;
}

static int thread_func(void* data) {
	unsigned long long n;
	while (!kthread_should_stop()) {
		printk(KERN_ALERT ">");
		hrtimer_cancel(&hr_timer);
		printk(KERN_ALERT "?");
		n=counter;
		msleep(PAUSE_MS);
		BUG_ON(n != counter);
		my_timer_forward(&hr_timer);
		printk(KERN_ALERT "<");
		hrtimer_start_expires(&hr_timer, HRTIMER_MODE_ABS);
		msleep(PAUSE_MS);
	}
	return 0;
}

static int hello_init(void) {

	printk(KERN_ALERT "Hello, world\n");
	hrtimer_init(&hr_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS);
	hr_timer.function = my_hrtimer_callback;
	my_timer_forward(&hr_timer);
	hrtimer_start_expires(&hr_timer, HRTIMER_MODE_ABS);
	t1 = kthread_run(thread_func, NULL, "my_thread");
  
	return 0;

}

 

static void hello_exit(void) {
	kthread_stop(t1);
	hrtimer_cancel(&hr_timer);
	printk(KERN_ALERT "Goodbye, cruel world\n");

}

 

module_init(hello_init);

module_exit(hello_exit);