a simple wait queue example for linux kernel

my_waitqueue.c

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* Copyright (c) 2015 Song Yang @ ittraining
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* This program is free to use, but the ban on selling behavior.
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#include <linux/module.h>
#include <linux/init.h>
#include <linux/sched.h>
#include <linux/time.h>
#include <linux/delay.h>
#include<linux/workqueue.h>

MODULE_LICENSE("GPL");
MODULE_AUTHOR("ITtraining.com.tw");
MODULE_DESCRIPTION("A Simple Blocking IO device RaspPi");

/* declare a wait queue*/
static wait_queue_head_t my_wait_queue;

/* declare a work queue*/
struct work_struct workq;
void my_workqueue_handler(struct work_struct *work)
{
	printk("WORK QUEUE: I'm just a timer to wake up the sleeping moudlue. \n");
	msleep(10000);  /* sleep */
	printk("WORK QUEUE: time up MODULE !! wake up !!!! \n");
	wake_up_interruptible(&my_wait_queue);
}

/*
 * INIT_MODULE -- MODULE START --
 * */
int init_module(void)
{
	printk("Wait queue example ....\n");

	// -- initialize the work queue
	INIT_WORK(&workq, my_workqueue_handler);
	schedule_work(&workq);

	// -- initialize the WAIT QUEUE head
	init_waitqueue_head(& my_wait_queue);

	printk("MODULE: This moudle is goint to sleep....\n");
	interruptible_sleep_on(&my_wait_queue);

	printk("MODULE: Wakeup Wakeup I am Waked up........\n");
	return 0;
}

/*
 * CLEANUP_MODULE -- MODULE END --
 * */
void cleanup_module(void)
{
	printk("<1> Start to cleanup \n");
}

Here is one with QEMU + Buildroot + BusyBox boilerplate for kernel 4.9: https://github.com/cirosantilli/linux-kernel-module-cheat/blob/e496f5d538f893d94b24f2779479f071cec40a5d/kernel_module/wait_queue.c

This looks like a race condition, shouldn't init_waitqueue_head be called before schedule_work? Otherwise, it's possible the thread could be pre-empted and the workqueue thread could call wake_up_interruptible before init_waitqueue_head was called. Right?

interruptible_sleep_on has been deprecated for a decade.

This program is free to use, but the ban on selling behavior.

This is a obvious violation of GPL. Please either remove MODULE_LICENSE("GPL"); or use a GPL compatible license.