#include <linux/module.h>
#include <linux/kthread.h>
#include <linux/hrtimer.h>

#define THREAD_PRIORITY (80)
#define THREAD_SCHEDULER SCHED_FIFO
#define MODULE_NAME "test-module"
#define KLOG_PREFIX MODULE_NAME ": "

struct task_struct *thread;
static ktime_t thread_next;
static ktime_t now;

/*
 * Threaded Runloop
 */
static int runloop(void *unused)
{

	int ret;

	/* Daemonize */
	daemonize(MODULE_NAME);

	/* Allow SIGTERM signal */
	allow_signal(SIGTERM);

	/* Calculate first shot */
	now = ktime_get();
	thread_next = ktime_add_us(now, 500);

	do {
		set_current_state(TASK_UNINTERRUPTIBLE);
		ret = schedule_hrtimeout(&thread_next, HRTIMER_MODE_ABS);
		if(ret == -EINTR)
		{
			printk(KERN_INFO KLOG_PREFIX "Signal received\n");
			continue;
		}

		thread_next = ktime_add_us(thread_next, 500);
	} while (!kthread_should_stop());

	printk(KERN_INFO KLOG_PREFIX "Thread exited\n");
	return 0;
}

int __init init_test_module(void)
{
	struct sched_param param = { .sched_priority = THREAD_PRIORITY };

	/* Kernel Thread erzeugen */
	if(thread == NULL)
		thread = kthread_create((void *)&runloop, NULL, "testthread");

	// Realtime scheduler
	sched_setscheduler(thread, THREAD_SCHEDULER, &param);
	wake_up_process(thread);
	return 0;
}

void __exit cleanup_test_module(void)
{
        if(thread != NULL)
                kthread_stop(thread);
        thread = NULL;
}

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Stefan Agner <stefan@anger.ch");
MODULE_DESCRIPTION("kthread test module");

module_init(init_test_module);
module_exit(cleanup_test_module);