Linux的hrtimer高精度定时器的使用

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/hrtimer.h>
#include <linux/ktime.h>

MODULE_LICENSE("GPL");

#define MS_TO_NS(x)	(x * 1E6L)//这个是定时器的超时时间，到了这个时间就会调用回调函数。
static struct hrtimer hr_timer;

enum hrtimer_restart my_hrtimer_callback( struct hrtimer *timer )
{
  printk( "my_hrtimer_callback called (%ld).\n", jiffies );

  hrtimer_start( &hr_timer, ktime, HRTIMER_MODE_REL );//到了这里再次调用就会不断的调用这个回调函数，两次调用时间间隔正是设定的超时时间
  return HRTIMER_NORESTART;}int init_module( void ){  ktime_t ktime;  unsigned long delay_in_ms = 200L;  printk("HR Timer module installing\n");  ktime = ktime_set( 0, MS_TO_NS(delay_in_ms) );  hrtimer_init( &hr_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL );  hr_timer.function = &my_hrtimer_callback;  printk( "Starting timer to fire in %ldms (%ld)\n", delay_in_ms, jiffies );  hrtimer_start( &hr_timer, ktime, HRTIMER_MODE_REL );  return 0;}void cleanup_module( void ){  int ret;  ret = hrtimer_cancel( &hr_timer );  if (ret) printk("The timer was still in use...\n");  printk("HR Timer module uninstalling\n");  return;}

注意：该定时器是异步执行的，类似于软中断和tasklet实现机制