kernel thread 테스트시 system이 hang 걸리는 이유가 궁금합니다.

#include <linux/init.h>
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/kthread.h>
 
static int int_value = 1;
static char *char_value = NULL;
 
module_param(int_value, int , 0);
module_param(char_value, charp, 0);
 
#define deb_main		printk
 
static DECLARE_WAIT_QUEUE_HEAD(thread_proc_wait);
 
struct task_struct *my_task;
 
static int thread_proc(void *unused)
{
	DECLARE_WAITQUEUE(wait, current);
	int thread_proc_count = 0;
	int i;
 
	deb_main("thread start\n");
 
	while(!kthread_should_stop())
	{
		thread_proc_count++;
		deb_main("thread processing %d\n", thread_proc_count);
		for(i=0; i<1000; i++) udelay(1000);
	}
 
	deb_main("set current state TASK_RUNNING\n");
	__set_current_state(TASK_RUNNING);
 
	deb_main("remove wait queue\n");
	remove_wait_queue(&thread_proc_wait, &wait);
 
	return 0;
}
 
static int hello_init(void)
{
	printk("Hello, World!!!\n");
	printk("int_value=%d, char_value=%s\n", int_value, char_value);
 
	my_task = kthread_create(thread_proc, NULL, "%s", "my_thread");
	if(my_task)
	{
		deb_main("thread start complete\n");
		wake_up_process(my_task);
	}
	deb_main("hello_init finish\n");
 
	return 0;
}
 
static void hello_exit(void)
{
	printk("Goodbye, World!!!\n");
	kthread_stop(my_task);
	deb_main("hello_exit finish\n");
}
 
module_init(hello_init);
module_exit(hello_exit);
 
MODULE_AUTHOR("Jade, Lee");
MODULE_DESCRIPTION("Kernel Module");
MODULE_LICENSE("Dual BSD/GPL");