/*	$OpenBSD: sched.c,v 1.13 2004/10/21 20:57:08 millert Exp $	*/

/*
 * Copyright (c) 1990 Jan-Simon Pendry
 * Copyright (c) 1990 Imperial College of Science, Technology & Medicine
 * Copyright (c) 1990, 1993
 *	The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Jan-Simon Pendry at Imperial College, London.
 *
 * 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.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS 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 REGENTS 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.
 *
 *	from: @(#)sched.c	8.1 (Berkeley) 6/6/93
 *	$Id: sched.c,v 1.13 2004/10/21 20:57:08 millert Exp $
 */

/*
 * Process scheduler
 */

#include "am.h"
#include <signal.h>
#include WAIT
#include <setjmp.h>
extern jmp_buf select_intr;
extern int select_intr_valid;

typedef struct pjob pjob;
struct pjob {
	qelem hdr;			/* Linked list */
	pid_t pid;			/* Process ID of job */
	cb_fun cb_fun;			/* Callback function */
	void *cb_closure;		/* Closure for callback */
	union wait w;			/* Status filled in by sigchld */
	void *wchan;			/* Wait channel */
};

extern qelem proc_list_head;
qelem proc_list_head = { &proc_list_head, &proc_list_head };
extern qelem proc_wait_list;
qelem proc_wait_list = { &proc_wait_list, &proc_wait_list };

int task_notify_todo;

void
ins_que(qelem *elem, qelem *pred)
{
	qelem *p = pred->q_forw;
	elem->q_back = pred;
	elem->q_forw = p;
	pred->q_forw = elem;
	p->q_back = elem;
}

void
rem_que(qelem *elem)
{
	qelem *p = elem->q_forw;
	qelem *p2 = elem->q_back;
	p2->q_forw = p;
	p->q_back = p2;
}

static pjob *
sched_job(cb_fun cf, void *ca)
{
	pjob *p = ALLOC(pjob);

	p->cb_fun = cf;
	p->cb_closure = ca;

	/*
	 * Now place on wait queue
	 */
	ins_que(&p->hdr, &proc_wait_list);

	return p;
}

void
run_task(task_fun tf, void *ta, cb_fun cf, void *ca)
{
	pjob *p = sched_job(cf, ca);
	sigset_t mask, omask;

	p->wchan = (void *)p;

	sigemptyset(&mask);
	sigaddset(&mask, SIGCHLD);
	sigprocmask(SIG_BLOCK, &mask, &omask);

	if ((p->pid = background())) {
		sigprocmask(SIG_SETMASK, &omask, NULL);
		return;
	}

	exit((*tf)(ta));
	/* firewall... */
	abort();
}

/*
 * Schedule a task to be run when woken up
 */
void
sched_task(cb_fun cf, void *ca, void *wchan)
{
	/*
	 * Allocate a new task
	 */
	pjob *p = sched_job(cf, ca);
#ifdef DEBUG_SLEEP
	dlog("SLEEP on %#x", wchan);
#endif
	p->wchan = wchan;
	p->pid = 0;
	bzero((void *)&p->w, sizeof(p->w));
}

static void
wakeupjob(pjob *p)
{
	rem_que(&p->hdr);
	ins_que(&p->hdr, &proc_list_head);
	task_notify_todo++;
}

void
wakeup(void *wchan)
{
	pjob *p, *p2;
#ifdef DEBUG_SLEEP
	int done = 0;
#endif
	if (!foreground)
		return;

#ifdef DEBUG_SLEEP
	/*dlog("wakeup(%#x)", wchan);*/
#endif
	/*
	 * Can't user ITER() here because
	 * wakeupjob() juggles the list.
	 */
	for (p = FIRST(pjob, &proc_wait_list);
			p2 = NEXT(pjob, p), p != HEAD(pjob, &proc_wait_list);
			p = p2) {
		if (p->wchan == wchan) {
#ifdef DEBUG_SLEEP
			done = 1;
#endif
			wakeupjob(p);
		}
	}

#ifdef DEBUG_SLEEP
	if (!done)
		dlog("Nothing SLEEPing on %#x", wchan);
#endif
}

void
wakeup_task(int rc, int term, void *cl)
{
	wakeup(cl);
}

/*ARGSUSED*/

void
sigchld(int sig)
{
	union wait w;
	int save_errno = errno;
	pid_t pid;

#ifdef SYS5_SIGNALS
	if ((pid = wait(&w)) > 0) {
#else
	while ((pid = wait3((int *) &w, WNOHANG, (struct rusage *) 0)) > 0) {
#endif /* SYS5_SIGNALS */
		pjob *p, *p2;

		if (WIFSIGNALED(w))
			plog(XLOG_ERROR, "Process %ld exited with signal %ld",
				(long)pid, w.w_termsig);
#ifdef DEBUG
		else
			dlog("Process %ld exited with status %ld",
				(long)pid, w.w_retcode);
#endif /* DEBUG */

		for (p = FIRST(pjob, &proc_wait_list);
				p2 = NEXT(pjob, p), p != HEAD(pjob, &proc_wait_list);
				p = p2) {
			if (p->pid == pid) {
				p->w = w;
				wakeupjob(p);
				break;
			}
		}

#ifdef DEBUG
		if (p == NULL)
			dlog("can't locate task block for pid %ld", (long)pid);
#endif /* DEBUG */
	}

#ifdef SYS5_SIGNALS
	signal(sig, sigchld);
#endif /* SYS5_SIGNALS */
	if (select_intr_valid)
		longjmp(select_intr, sig);
	errno = save_errno;
}

/*
 * Run any pending tasks.
 * This must be called with SIGCHLD disabled
 */
void
do_task_notify(void)
{
	/*
	 * Keep taking the first item off the list and processing it.
	 *
	 * Done this way because the callback can, quite reasonably,
	 * queue a new task, so no local reference into the list can be
	 * held here.
	 */
	while (FIRST(pjob, &proc_list_head) != HEAD(pjob, &proc_list_head)) {
		pjob *p = FIRST(pjob, &proc_list_head);
		rem_que(&p->hdr);
		/*
		 * This job has completed
		 */
		--task_notify_todo;

		/*
		 * Do callback if it exists
		 */
		if (p->cb_fun)
			(*p->cb_fun)(p->w.w_retcode,
				p->w.w_termsig, p->cb_closure);

		free((void *)p);
	}
}