Function kthread_add

freebsd/kern/kern_kthread.c:263–332

* Create a kernel thread. It shares its address space * with proc0 - ie: kernel only. * * func is the function to start. * arg is the parameter to pass to function on first startup. * newtdp is the return value pointing to the thread's struct thread. * ** XXX fix this --> flags are flags to fork1 (in unistd.h) * fmt and following will be *printf'd into (*newtd)->td_name (for ps, etc.).

 * fmt and following will be *printf'd into (*newtd)->td_name (for ps, etc.).
 */
int
kthread_add(void (*func)(void *), void *arg, struct proc *p,
    struct thread **newtdp, int flags, int pages, const char *fmt, ...)
{
	va_list ap;
	struct thread *newtd, *oldtd;

	if (!proc0.p_stats)
		panic("kthread_add called too soon");

	/* If no process supplied, put it on proc0 */
	if (p == NULL)
		p = &proc0;

	/* Initialize our new td  */
	newtd = thread_alloc(pages);
	if (newtd == NULL)
		return (ENOMEM);

	PROC_LOCK(p);
	oldtd = FIRST_THREAD_IN_PROC(p);

	bzero(&newtd->td_startzero,
	    __rangeof(struct thread, td_startzero, td_endzero));
	bcopy(&oldtd->td_startcopy, &newtd->td_startcopy,
	    __rangeof(struct thread, td_startcopy, td_endcopy));

	/* set up arg0 for 'ps', et al */
	va_start(ap, fmt);
	vsnprintf(newtd->td_name, sizeof(newtd->td_name), fmt, ap);
	va_end(ap);

	TSTHREAD(newtd, newtd->td_name);

	newtd->td_proc = p;  /* needed for cpu_copy_thread */
	/* might be further optimized for kthread */
	cpu_copy_thread(newtd, oldtd);
	/* put the designated function(arg) as the resume context */
	cpu_fork_kthread_handler(newtd, func, arg);

	newtd->td_pflags |= TDP_KTHREAD;
	thread_cow_get_proc(newtd, p);

	/* this code almost the same as create_thread() in kern_thr.c */
	p->p_flag |= P_HADTHREADS;
	thread_link(newtd, p);
	thread_lock(oldtd);
	/* let the scheduler know about these things. */
	sched_fork_thread(oldtd, newtd);
	TD_SET_CAN_RUN(newtd);
	thread_unlock(oldtd);
	PROC_UNLOCK(p);

	tidhash_add(newtd);

	/* Avoid inheriting affinity from a random parent. */
	cpuset_kernthread(newtd);
#ifdef HWPMC_HOOKS