FreeBSD taskqueue(9) example

Makefile

SRCS=taskqueue_example.c
KMOD=taskqueue_example

.include <bsd.kmod.mk>

taskqueue_example.c

/* This is an example taskqueue(9) on FreeBSD.
 * All it does is create a scheduled task and execute it almost immediately.
 * I wrote this because I did not understand the taskqueue(9) man page, so I
 * read the FreeBSD kernel source.
 * My question: https://docs.freebsd.org/cgi/getmsg.cgi?fetch=12990+0+current/freebsd-hackers
 * Answer: https://docs.freebsd.org/cgi/getmsg.cgi?fetch=17373+0+current/freebsd-hackers
 */

#include <sys/types.h>
#include <sys/module.h>
#include <sys/systm.h>
#include <sys/errno.h>
#include <sys/param.h>
#include <sys/kernel.h>
#include <sys/queue.h>
#include <sys/taskqueue.h>
#include <sys/malloc.h>

void static threadqueue_example_proc(void *, int);
void init_threadqueue_example(void);

struct taskqueue;

struct taskq {
	struct taskqueue *tq_queue;
} *tq;

struct controller {
	struct task x_task;
} *ctrl;

static void
threadqueue_example_proc(void *arg, int npending) {
	char *str = arg;
	printf("Got message: %s\n", str);
}

void
init_threadqueue_example()
{

	tq = malloc(sizeof(struct taskq), M_TEMP, M_WAITOK);
	ctrl = malloc(sizeof(struct controller), M_TEMP, M_WAITOK);

	TASK_INIT(&ctrl->x_task, 0, threadqueue_example_proc, "Farhan");

	tq->tq_queue = taskqueue_create("farhan", M_NOWAIT | M_ZERO,
		taskqueue_thread_enqueue, &tq->tq_queue);

	taskqueue_start_threads(&tq->tq_queue, 1, PI_DISK, "%s name", "ABC");

	taskqueue_enqueue(tq->tq_queue, &ctrl->x_task);
}

static int
threadqueue_example_loader(struct module *m, int what, void *arg)
{
	int err = 0;

	switch (what) {
	case MOD_LOAD:
		init_threadqueue_example();
		uprintf("Repeater KLD loaded.\n");
		break;
	case MOD_UNLOAD:
		uprintf("Repeater KLD unloaded.\n");
		break;
	}
	return(err);
}

static moduledata_t threadqueue_example_mod = {
	"taskqueue_example",
	threadqueue_example_loader,
	NULL
};

DECLARE_MODULE(threadqueue_example, threadqueue_example_mod, SI_SUB_KLD, SI_ORDER_ANY);