text: /*
   * Copyright (c) 1999 Peter Wemm <peter@FreeBSD.org>
   * All rights reserved.
   *
   * 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 AUTHOR 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 AUTHOR 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.
   *
   * $FreeBSD: src/sys/kern/kern_kthread.c,v 1.5.2.3 2001/12/25 01:51:14 dillon Exp $
   */
  
  #include <sys/param.h>
  #include <sys/systm.h>
  #include <sys/proc.h>
  #include <sys/kthread.h>
  #include <sys/ptrace.h>
  #include <sys/resourcevar.h>
  #include <sys/signalvar.h>
  #include <sys/unistd.h>
  #include <sys/wait.h>
  
  #include <machine/stdarg.h>
  
  /*
   * Start a kernel process.  This is called after a fork() call in
   * mi_startup() in the file kern/init_main.c.
   *
   * This function is used to start "internal" daemons and intended
   * to be called from SYSINIT().
   */
  void
  kproc_start(udata)
  	const void *udata;
  {
  	const struct kproc_desc	*kp = udata;
  	int error;
  
  	error = kthread_create((void (*)(void *))kp->func, NULL,
  		    kp->global_procpp, kp->arg0);
  	if (error)
  		panic("kproc_start: %s: error %d", kp->arg0, error);
  }
  
  /*
   * Create a kernel process/thread/whatever.  It shares it's address space
   * with proc0 - ie: kernel only.
   */
  int
  kthread_create(void (*func)(void *), void *arg,
      struct proc **newpp, const char *fmt, ...)
  {
  	int error;
  	va_list ap;
  	struct proc *p2;
  
  	if (!proc0.p_stats /* || proc0.p_stats->p_start.tv_sec == 0 */) {
  		panic("kthread_create called too soon");
  	}
  
  	error = fork1(&proc0, RFMEM | RFFDG | RFPROC, &p2);
  	if (error)
  		return error;
  
  	/* save a global descriptor, if desired */
  	if (newpp != NULL)
  		*newpp = p2;
  
  	/* this is a non-swapped system process */
  	p2->p_flag |= P_INMEM | P_SYSTEM;
  	p2->p_procsig->ps_flag |= PS_NOCLDWAIT;
  	PHOLD(p2);
  
  	/* set up arg0 for 'ps', et al */
  	va_start(ap, fmt);
  	vsnprintf(p2->p_comm, sizeof(p2->p_comm), fmt, ap);
  	va_end(ap);
  
  	/* call the processes' main()... */
  	cpu_set_fork_handler(p2, func, arg);
  
  	return 0;
  }
  
  void
  kthread_exit(int ecode)
  {
  	proc_reparent(curproc, initproc);
  	exit1(curproc, W_EXITCODE(ecode, 0));
  }
  
  /*
   * Advise a kernel process to suspend (or resume) in its main loop.
   * Participation is voluntary.
   */
  int
  suspend_kproc(struct proc *p, int timo)
  {
  	/*
  	 * Make sure this is indeed a system process and we can safely
  	 * use the p_siglist field.
  	 */
  	if ((p->p_flag & P_SYSTEM) == 0)
  		return (EINVAL);
  	SIGADDSET(p->p_siglist, SIGSTOP);
  	wakeup(p);
  	return tsleep((caddr_t)&p->p_siglist, PPAUSE, "suspkp", timo);
  }
  
  int
  resume_kproc(struct proc *p)
  {
  	/*
  	 * Make sure this is indeed a system process and we can safely
  	 * use the p_siglist field.
  	 */
  	if ((p->p_flag & P_SYSTEM) == 0)
  		return (EINVAL);
  	SIGDELSET(p->p_siglist, SIGSTOP);
  	wakeup((caddr_t)&p->p_siglist);
  	return (0);
  }
  
  void
  kproc_suspend_loop(struct proc *p)
  {
  	while (SIGISMEMBER(p->p_siglist, SIGSTOP)) {
  		wakeup((caddr_t)&p->p_siglist);
  		tsleep((caddr_t)&p->p_siglist, PPAUSE, "kpsusp", 0);
  	}
  }
  