/*
 * Taken from Linux Device Drivers, 3rd Edition.
 * Corbet, Rubini, and Kroah-Hartman.
 *
 * Modified by Paul E. McKenney (c) 2008 to test CPU-stall detection.
 */

#include <linux/init.h>
#include <linux/module.h>
#include <linux/sched.h>
#include <linux/kthread.h>
#include <linux/err.h>
#include <linux/time.h>
MODULE_LICENSE("Dual BSD/GPL");

int stall_secs = 0;
module_param(stall_secs, int, 0);
MODULE_PARM_DESC(stall_secs, "Number of seconds to stall");

static struct task_struct *kstall_task;

static int stall_thread(void *arg)
{
	unsigned long stop_at;

	printk(KERN_ALERT "stall_thread %ld\n", (long)arg);
	do {
		stop_at = get_seconds();
		printk(KERN_ALERT "stall_thread at %ld seconds\n", stop_at);
		stop_at += stall_secs;
		printk(KERN_ALERT "stall_thread wait until %ld seconds\n", stop_at);
		while ((long)(get_seconds() - stop_at) < 0)
			continue;
		printk(KERN_ALERT "stall_thread ended wait at %ld seconds\n", get_seconds());
		set_current_state(TASK_UNINTERRUPTIBLE);
		schedule_timeout(10 * HZ);
		printk(KERN_ALERT "stall_thread %ld awakening\n", (long)arg);
	} while (!kthread_should_stop());
	printk(KERN_ALERT "stall_thread %ld exiting\n", (long)arg);
	return 0;
}

static int stall_init(void)
{
	int err;

	printk(KERN_ALERT "Hello, world!  stall_secs = %d\n", stall_secs);
	kstall_task = kthread_run(stall_thread, (void *)(long)stall_secs,
				  "stall_thread");
	if (IS_ERR(kstall_task)) {
		err = PTR_ERR(kstall_task);
		kstall_task = NULL;
		return err;
	}
	return 0;
}

static void stall_exit(void)
{
	if (kstall_task != NULL) {
		kthread_stop(kstall_task);
	}
	kstall_task = NULL;
	printk(KERN_ALERT "Goodbye, cruel world\n");
}

module_init(stall_init);
module_exit(stall_exit);