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Mark exit1() and sigexit() as non-returning

The late 1990s reasons for avoiding __dead with exit1() should not apply
with the current compilers.

This fixes compiler warnings about uninitialized variables in trap.c
on mips64.

Discussed with guenther@ and miod@

/*	$OpenBSD: kern_kthread.c,v 1.46 2021/11/26 04:42:13 visa Exp $	*/
/*	$NetBSD: kern_kthread.c,v 1.3 1998/12/22 21:21:36 kleink Exp $	*/

/*-
 * Copyright (c) 1998, 1999 The NetBSD Foundation, Inc.
 * All rights reserved.
 *
 * This code is derived from software contributed to The NetBSD Foundation
 * by Jason R. Thorpe of the Numerical Aerospace Simulation Facility,
 * NASA Ames Research Center.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kthread.h>
#include <sys/proc.h>
#include <sys/malloc.h>
#include <sys/queue.h>

int	kthread_create_now;

/*
 * Fork a kernel thread.  Any process can request this to be done.
 * The VM space and limits, etc. will be shared with proc0.
 */
int
kthread_create(void (*func)(void *), void *arg,
    struct proc **newpp, const char *name)
{
	struct proc *p;
	int error;

	KERNEL_LOCK();

	/*
	 * First, create the new process.  Share the memory, file
	 * descriptors and don't leave the exit status around for the
	 * parent to wait for.
	 */
	error = fork1(&proc0, FORK_SHAREVM|FORK_SHAREFILES|FORK_NOZOMBIE|
	    FORK_SYSTEM, func, arg, NULL, &p);
	if (error) {
		KERNEL_UNLOCK();
		return (error);
	}

	/* Name it as specified. */
	strlcpy(p->p_p->ps_comm, name, sizeof p->p_p->ps_comm);

	KERNEL_UNLOCK();

	/* All done! */
	if (newpp != NULL)
		*newpp = p;
	return (0);
}

/*
 * Cause a kernel thread to exit.  Assumes the exiting thread is the
 * current context.
 */
void
kthread_exit(int ecode)
{

	/*
	 * XXX What do we do with the exit code?  Should we even bother
	 * XXX with it?  The parent (proc0) isn't going to do much with
	 * XXX it.
	 */
	if (ecode != 0)
		printf("WARNING: thread `%s' (%d) exits with status %d\n",
		    curproc->p_p->ps_comm, curproc->p_tid, ecode);

	exit1(curproc, ecode, 0, EXIT_NORMAL);
	/* NOTREACHED */
}

struct kthread_q {
	SIMPLEQ_ENTRY(kthread_q) kq_q;
	void (*kq_func)(void *);
	void *kq_arg;
};

SIMPLEQ_HEAD(, kthread_q) kthread_q = SIMPLEQ_HEAD_INITIALIZER(kthread_q);

/*
 * Defer the creation of a kernel thread.  Once the standard kernel threads
 * and processes have been created, this queue will be run to callback to
 * the caller to create threads for e.g. file systems and device drivers.
 */
void
kthread_create_deferred(void (*func)(void *), void *arg)
{
	struct kthread_q *kq;

	if (kthread_create_now) {
		(*func)(arg);
		return;
	}

	kq = malloc(sizeof *kq, M_TEMP, M_NOWAIT|M_ZERO);
	if (kq == NULL)
		panic("unable to allocate kthread_q");

	kq->kq_func = func;
	kq->kq_arg = arg;

	SIMPLEQ_INSERT_TAIL(&kthread_q, kq, kq_q);
}

void
kthread_run_deferred_queue(void)
{
	struct kthread_q *kq;

	/* No longer need to defer kthread creation. */
	kthread_create_now = 1;

	while ((kq = SIMPLEQ_FIRST(&kthread_q)) != NULL) {
		SIMPLEQ_REMOVE_HEAD(&kthread_q, kq_q);
		(*kq->kq_func)(kq->kq_arg);
		free(kq, M_TEMP, sizeof(*kq));
	}
}