/*      $NetBSD: sched.c,v 1.1.1.3 2015/01/17 16:34:15 christos Exp $   */

/*
* Copyright (c) 1997-2014 Erez Zadok
* Copyright (c) 1990 Jan-Simon Pendry
* Copyright (c) 1990 Imperial College of Science, Technology & Medicine
* Copyright (c) 1990 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.
*
*
* File: am-utils/amd/sched.c
*
*/

/*
* Process scheduler
*/

#ifdef HAVE_CONFIG_H
# include <config.h>
#endif /* HAVE_CONFIG_H */
#include <am_defs.h>
#include <amd.h>


typedef struct pjob pjob;

struct pjob {
 qelem hdr;            /* Linked list */
 int pid;              /* Process ID of job */
 cb_fun *cb_fun;       /* Callback function */
 opaque_t cb_arg;      /* Argument for callback */
 int w;                /* everyone these days uses int, not a "union wait" */
 wchan_t wchan;        /* Wait channel */
};

/* globals */
qelem proc_list_head = {&proc_list_head, &proc_list_head};
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, opaque_t ca)
{
 pjob *p = ALLOC(struct pjob);

 p->cb_fun = cf;
 p->cb_arg = ca;

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

 return p;
}


/*
* tf: The task to execute (ta is its arguments)
* cf: Continuation function (ca is its arguments)
*/
void
run_task(task_fun *tf, opaque_t ta, cb_fun *cf, opaque_t ca)
{
 pjob *p = sched_job(cf, ca);
#ifdef HAVE_SIGACTION
 sigset_t new, mask;
#else /* not HAVE_SIGACTION */
 int mask;
#endif /* not HAVE_SIGACTION */

 p->wchan = (wchan_t) p;

#ifdef HAVE_SIGACTION
 sigemptyset(&new);            /* initialize signal set we wish to block */
 sigaddset(&new, SIGCHLD);     /* only block on SIGCHLD */
 sigprocmask(SIG_BLOCK, &new, &mask);
#else /* not HAVE_SIGACTION */
 mask = sigblock(sigmask(SIGCHLD));
#endif /* not HAVE_SIGACTION */

 if ((p->pid = background())) {
#ifdef HAVE_SIGACTION
   sigprocmask(SIG_SETMASK, &mask, NULL);
#else /* not HAVE_SIGACTION */
   sigsetmask(mask);
#endif /* not HAVE_SIGACTION */
   return;
 }

 /* child code runs here, parent has returned to caller */

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


/*
* Schedule a task to be run when woken up
*/
void
sched_task(cb_fun *cf, opaque_t ca, wchan_t wchan)
{
 /*
  * Allocate a new task
  */
 pjob *p = sched_job(cf, ca);

 dlog("SLEEP on %p", wchan);
 p->wchan = wchan;
 p->pid = 0;
 p->w = 0;                     /* was memset (when ->w was union) */
}


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


void
wakeup(wchan_t wchan)
{
 pjob *p, *p2;

 if (!foreground)
   return;

 /*
  * Can't use ITER() here because
  * wakeupjob() juggles the list.
  */
 for (p = AM_FIRST(pjob, &proc_wait_list);
      p2 = NEXT(pjob, p), p != HEAD(pjob, &proc_wait_list);
      p = p2) {
   if (p->wchan == wchan) {
     wakeupjob(p);
   }
 }
}


void
wakeup_task(int rc, int term, wchan_t wchan)
{
 wakeup(wchan);
}


wchan_t
get_mntfs_wchan(mntfs *mf)
{
 if (mf &&
     mf->mf_ops &&
     mf->mf_ops->get_wchan)
   return mf->mf_ops->get_wchan(mf);
 return mf;
}


/*
* 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 (AM_FIRST(pjob, &proc_list_head) != HEAD(pjob, &proc_list_head)) {
   pjob *p = AM_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) {
     /* these two trigraphs will ensure compatibility with strict POSIX.1 */
     p->cb_fun(WIFEXITED(p->w)   ? WEXITSTATUS(p->w) : 0,
               WIFSIGNALED(p->w) ? WTERMSIG(p->w)    : 0,
               p->cb_arg);
   }
   XFREE(p);
 }
}


RETSIGTYPE
sigchld(int sig)
{
 int w;        /* everyone these days uses int, not a "union wait" */
 int pid;

#ifdef HAVE_WAITPID
 while ((pid = waitpid((pid_t) -1,  &w, WNOHANG)) > 0) {
#else /* not HAVE_WAITPID */
 while ((pid = wait3( &w, WNOHANG, (struct rusage *) NULL)) > 0) {
#endif /* not HAVE_WAITPID */
   pjob *p, *p2;

   if (WIFSIGNALED(w))
     plog(XLOG_ERROR, "Process %d exited with signal %d",
          pid, WTERMSIG(w));
   else
     dlog("Process %d exited with status %d",
          pid, WEXITSTATUS(w));

   for (p = AM_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;
     }
   } /* end of for loop */

   if (p == HEAD(pjob, &proc_wait_list))
     dlog("can't locate task block for pid %d", pid);

   /*
    * Must count down children inside the while loop, otherwise we won't
    * count them all, and NumChildren (and later backoff) will be set
    * incorrectly. SH/RUNIT 940519.
    */
   if (--NumChildren < 0)
     NumChildren = 0;
 } /* end of "while wait..." loop */

#ifdef REINSTALL_SIGNAL_HANDLER
 signal(sig, sigchld);
#endif /* REINSTALL_SIGNAL_HANDLER */

 if (select_intr_valid)
   longjmp(select_intr, sig);
}

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