/* 
 * The contents of this file are subject to the Mozilla Public
 * License Version 1.1 (the "License"); you may not use this file
 * except in compliance with the License. You may obtain a copy of
 * the License at http://www.mozilla.org/MPL/
 * 
 * Software distributed under the License is distributed on an "AS
 * IS" basis, WITHOUT WARRANTY OF ANY KIND, either express or
 * implied. See the License for the specific language governing
 * rights and limitations under the License.
 * 
 * The Original Code is the Netscape Portable Runtime library.
 * 
 * The Initial Developer of the Original Code is Netscape
 * Communications Corporation.  Portions created by Netscape are 
 * Copyright (C) 1994-2000 Netscape Communications Corporation.  All
 * Rights Reserved.
 * 
 * Contributor(s):  Silicon Graphics, Inc.
 * 
 * Portions created by SGI are Copyright (C) 2000-2001 Silicon
 * Graphics, Inc.  All Rights Reserved.
 * 
 * Alternatively, the contents of this file may be used under the
 * terms of the GNU General Public License Version 2 or later (the
 * "GPL"), in which case the provisions of the GPL are applicable 
 * instead of those above.  If you wish to allow use of your 
 * version of this file only under the terms of the GPL and not to
 * allow others to use your version of this file under the MPL,
 * indicate your decision by deleting the provisions above and
 * replace them with the notice and other provisions required by
 * the GPL.  If you do not delete the provisions above, a recipient
 * may use your version of this file under either the MPL or the
 * GPL.
 */

/*
 * This file is derived directly from Netscape Communications Corporation,
 * and consists of extensive modifications made during the year(s) 1999-2000.
 */

#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>
#include <string.h>
#include <time.h>
#include <errno.h>
#include "common.h"


/* Global data */
_st_vp_t _st_this_vp;           /* This VP */
_st_thread_t *_st_this_thread;  /* Current thread */
int _st_active_count = 0;       /* Active thread count */

time_t _st_curr_time = 0;       /* Current time as returned by time(2) */
st_utime_t _st_last_tset;       /* Last time it was fetched */


int st_poll(struct pollfd *pds, int npds, st_utime_t timeout)
{
  struct pollfd *pd;
  struct pollfd *epd = pds + npds;
  _st_pollq_t pq;
  _st_thread_t *me = _ST_CURRENT_THREAD();
  int n;

  if (me->flags & _ST_FL_INTERRUPT) {
    me->flags &= ~_ST_FL_INTERRUPT;
    errno = EINTR;
    return -1;
  }

#ifndef USE_POLL
  for (pd = pds; pd < epd; pd++) {
    if (pd->events & POLLIN) {
      FD_SET(pd->fd, &_ST_FD_READ_SET);
      _ST_FD_READ_CNT(pd->fd)++;
    }
    if (pd->events & POLLOUT) {
      FD_SET(pd->fd, &_ST_FD_WRITE_SET);
      _ST_FD_WRITE_CNT(pd->fd)++;
    }
    if (pd->events & POLLPRI) {
      FD_SET(pd->fd, &_ST_FD_EXCEPTION_SET);
      _ST_FD_EXCEPTION_CNT(pd->fd)++;
    }
    if (_ST_MAX_OSFD < pd->fd)
      _ST_MAX_OSFD = pd->fd;
  }
#else
  _ST_OSFD_CNT += npds;
#endif  /* !USE_POLL */

  pq.pds = pds;
  pq.npds = npds;
  pq.thread = me;
  pq.on_ioq = 1;
  _ST_ADD_IOQ(pq);
  if (timeout != ST_UTIME_NO_TIMEOUT)
    _ST_ADD_SLEEPQ(me, timeout);
  me->state = _ST_ST_IO_WAIT;

  _ST_SWITCH_CONTEXT(me);

  n = 0;
  if (pq.on_ioq) {
    /* If we timed out, the pollq might still be on the ioq. Remove it */
    _ST_DEL_IOQ(pq);
#ifndef USE_POLL
    for (pd = pds; pd < epd; pd++) {
      if (pd->events & POLLIN) {
	if (--_ST_FD_READ_CNT(pd->fd) == 0)
	  FD_CLR(pd->fd, &_ST_FD_READ_SET);
      }
      if (pd->events & POLLOUT) {
	if (--_ST_FD_WRITE_CNT(pd->fd) == 0)
	  FD_CLR(pd->fd, &_ST_FD_WRITE_SET);
      }
      if (pd->events & POLLPRI) {
	if (--_ST_FD_EXCEPTION_CNT(pd->fd) == 0)
	  FD_CLR(pd->fd, &_ST_FD_EXCEPTION_SET);
      }
    }
#else
    _ST_OSFD_CNT -= npds;
    ST_ASSERT(_ST_OSFD_CNT >= 0);
#endif  /* !USE_POLL */
  } else {
    /* Count the number of ready descriptors */
    for (pd = pds; pd < epd; pd++) {
      if (pd->revents)
	n++;
    }
  }

  if (me->flags & _ST_FL_INTERRUPT) {
    me->flags &= ~_ST_FL_INTERRUPT;
    errno = EINTR;
    return -1;
  }

  return n;
}


void _st_vp_schedule(void)
{
  _st_thread_t *thread;

  if (_ST_RUNQ.next != &_ST_RUNQ) {
    /* Pull thread off of the run queue */
    thread = _ST_THREAD_PTR(_ST_RUNQ.next);
    _ST_DEL_RUNQ(thread);
  } else {
    /* If there are no threads to run, switch to the idle thread */
    thread = _st_this_vp.idle_thread;
  }
  ST_ASSERT(thread->state == _ST_ST_RUNNABLE);

  /* Resume the thread */
  thread->state = _ST_ST_RUNNING;
  _ST_RESTORE_CONTEXT(thread);
}


/*
 * Initialize this Virtual Processor
 */
int st_init(void)
{
  _st_thread_t *thread;

  if (_st_active_count) {
    /* Already initialized */
    return 0;
  }

  if (_st_io_init() < 0)
    return -1;

  memset(&_st_this_vp, 0, sizeof(_st_vp_t));

  ST_INIT_CLIST(&_ST_RUNQ);
  ST_INIT_CLIST(&_ST_IOQ);
  ST_INIT_CLIST(&_ST_ZOMBIEQ);
#ifdef DEBUG
  ST_INIT_CLIST(&_ST_THREADQ);
#endif

#ifndef USE_POLL
  _st_this_vp.maxfd = -1;
#else
  _ST_POLLFDS = (struct pollfd *) malloc(ST_MIN_POLLFDS_SIZE *
					 sizeof(struct pollfd));
  if (!_ST_POLLFDS)
    return -1;
  _ST_POLLFDS_SIZE = ST_MIN_POLLFDS_SIZE;
#endif  /* !USE_POLL */
  _st_this_vp.pagesize = getpagesize();
  _st_this_vp.last_clock = st_utime();

  /*
   * Create idle thread
   */
  _st_this_vp.idle_thread = st_thread_create(_st_idle_thread_start,
					     NULL, 0, 0);
  if (!_st_this_vp.idle_thread)
    return -1;
  _st_this_vp.idle_thread->flags = _ST_FL_IDLE_THREAD;
  _st_active_count--;
  _ST_DEL_RUNQ(_st_this_vp.idle_thread);

  /*
   * Initialize primordial thread
   */
  thread = (_st_thread_t *) calloc(1, sizeof(_st_thread_t) +
				   (ST_KEYS_MAX * sizeof(void *)));
  if (!thread)
    return -1;
  thread->private_data = (void **) (thread + 1);
  thread->state = _ST_ST_RUNNING;
  thread->flags = _ST_FL_PRIMORDIAL;
  _ST_SET_CURRENT_THREAD(thread);
  _st_active_count++;
#ifdef DEBUG
  _ST_ADD_THREADQ(thread);
#endif

  return 0;
}


/*
 * Start function for the idle thread
 */
/* ARGSUSED */
void *_st_idle_thread_start(void *arg)
{
  _st_thread_t *me = _ST_CURRENT_THREAD();

  while (_st_active_count > 0) {
    /* Idle vp till I/O is ready or the smallest timeout expired */
    _st_vp_idle();

    /* Check sleep queue for expired threads */
    _st_vp_check_clock();

    me->state = _ST_ST_RUNNABLE;
    _ST_SWITCH_CONTEXT(me);
  }

  /* No more threads */
  exit(0);

  /* NOTREACHED */
  return NULL;
}


#ifndef USE_POLL
/* select() is used to poll file descriptors */
void _st_vp_idle(void)
{
  struct timeval timeout, *tvp;
  fd_set r, w, e;
  fd_set *rp, *wp, *ep;
  int nfd, pq_max_osfd, osfd;
  _st_clist_t *q;
  st_utime_t min_timeout;
  _st_pollq_t *pq;
  int notify;
  struct pollfd *pds, *epds;
  short events, revents;

  /*
   * Assignment of fd_sets
   */
  r = _ST_FD_READ_SET;
  w = _ST_FD_WRITE_SET;
  e = _ST_FD_EXCEPTION_SET;

  rp = &r;
  wp = &w;
  ep = &e;

  if (_ST_SLEEPQ == NULL) {
    tvp = NULL;
  } else {
    min_timeout = (_ST_SLEEPQ->due <= _ST_LAST_CLOCK) ? 0 :
      (_ST_SLEEPQ->due - _ST_LAST_CLOCK);
    timeout.tv_sec  = (int) (min_timeout / 1000000);
    timeout.tv_usec = (int) (min_timeout % 1000000);
    tvp = &timeout;
  }

  /* Check for I/O operations */
  nfd = select(_ST_MAX_OSFD + 1, rp, wp, ep, tvp);

  /* Notify threads that are associated with the selected descriptors */
  if (nfd > 0) {
    _ST_MAX_OSFD = -1;
    for (q = _ST_IOQ.next; q != &_ST_IOQ; q = q->next) {
      pq = _ST_POLLQUEUE_PTR(q);
      notify = 0;
      epds = pq->pds + pq->npds;
      pq_max_osfd = -1;
      
      for (pds = pq->pds; pds < epds; pds++) {
	osfd = pds->fd;
	events = pds->events;
	revents = 0;
	ST_ASSERT(osfd >= 0 || events == 0);
	if ((events & POLLIN) && FD_ISSET(osfd, rp)) {
	  revents |= POLLIN;
	}
	if ((events & POLLOUT) && FD_ISSET(osfd, wp)) {
	  revents |= POLLOUT;
	}
	if ((events & POLLPRI) && FD_ISSET(osfd, ep)) {
	  revents |= POLLPRI;
	}
	pds->revents = revents;
	if (revents) {
	  notify = 1;
	}
	if (osfd > pq_max_osfd) {
	  pq_max_osfd = osfd;
	}
      }
      if (notify) {
	ST_REMOVE_LINK(&pq->links);
	pq->on_ioq = 0;
	/*
	 * Decrement the count of descriptors for each descriptor/event
	 * because this I/O request is being removed from the ioq
	 */
	for (pds = pq->pds; pds < epds; pds++) {
	  osfd = pds->fd;
	  events = pds->events;
	  if (events & POLLIN) {
	    if (--_ST_FD_READ_CNT(osfd) == 0) {
	      FD_CLR(osfd, &_ST_FD_READ_SET);
	    }
	  }
	  if (events & POLLOUT) {
	    if (--_ST_FD_WRITE_CNT(osfd) == 0) {
	      FD_CLR(osfd, &_ST_FD_WRITE_SET);
	    }
	  }
	  if (events & POLLPRI) {
	    if (--_ST_FD_EXCEPTION_CNT(osfd) == 0) {
	      FD_CLR(osfd, &_ST_FD_EXCEPTION_SET);
	    }
	  }
	}

	if (pq->thread->flags & _ST_FL_ON_SLEEPQ)
	  _ST_DEL_SLEEPQ(pq->thread);
	pq->thread->state = _ST_ST_RUNNABLE;
	_ST_ADD_RUNQ(pq->thread);
      } else {
	if (_ST_MAX_OSFD < pq_max_osfd)
	  _ST_MAX_OSFD = pq_max_osfd;
      }
    }
  } else if (nfd < 0) {
    /*
     * It can happen when a thread closes file descriptor
     * that is being used by some other thread
     */
    if (errno == EBADF)
      _st_find_bad_fd();
  }
}


void _st_find_bad_fd(void)
{
  _st_clist_t *q;
  _st_pollq_t *pq;
  int notify;
  struct pollfd *pds, *epds;
  int pq_max_osfd, osfd;
  short events;

  _ST_MAX_OSFD = -1;

  for (q = _ST_IOQ.next; q != &_ST_IOQ; q = q->next) {
    pq = _ST_POLLQUEUE_PTR(q);
    notify = 0;
    epds = pq->pds + pq->npds;
    pq_max_osfd = -1;
      
    for (pds = pq->pds; pds < epds; pds++) {
      osfd = pds->fd;
      pds->revents = 0;
      ST_ASSERT(osfd >= 0 || pds->events == 0);
      if (pds->events == 0)
	continue;
      if (fcntl(osfd, F_GETFL, 0) < 0) {
	pds->revents = POLLNVAL;
	notify = 1;
      }
      if (osfd > pq_max_osfd) {
	pq_max_osfd = osfd;
      }
    }

    if (notify) {
      ST_REMOVE_LINK(&pq->links);
      pq->on_ioq = 0;
      /*
       * Decrement the count of descriptors for each descriptor/event
       * because this I/O request is being removed from the ioq
       */
      for (pds = pq->pds; pds < epds; pds++) {
	osfd = pds->fd;
	events = pds->events;
	if (events & POLLIN) {
	  if (--_ST_FD_READ_CNT(osfd) == 0) {
	    FD_CLR(osfd, &_ST_FD_READ_SET);
	  }
	}
	if (events & POLLOUT) {
	  if (--_ST_FD_WRITE_CNT(osfd) == 0) {
	    FD_CLR(osfd, &_ST_FD_WRITE_SET);
	  }
	}
	if (events & POLLPRI) {
	  if (--_ST_FD_EXCEPTION_CNT(osfd) == 0) {
	    FD_CLR(osfd, &_ST_FD_EXCEPTION_SET);
	  }
	}
      }

      if (pq->thread->flags & _ST_FL_ON_SLEEPQ)
	_ST_DEL_SLEEPQ(pq->thread);
      pq->thread->state = _ST_ST_RUNNABLE;
      _ST_ADD_RUNQ(pq->thread);
    } else {
      if (_ST_MAX_OSFD < pq_max_osfd)
	_ST_MAX_OSFD = pq_max_osfd;
    }
  }
}

#else  /* !USE_POLL */
/* poll() is used to poll file descriptors */
void _st_vp_idle(void)
{
  int timeout, nfd;
  _st_clist_t *q;
  st_utime_t min_timeout;
  _st_pollq_t *pq;
  struct pollfd *pds, *epds, *pollfds;

  /*
   * Build up the array of struct pollfd to wait on.
   * If existing array is not big enough, release it and allocate a new one.
   */
  ST_ASSERT(_ST_OSFD_CNT >= 0);
  if (_ST_OSFD_CNT > _ST_POLLFDS_SIZE) {
    free(_ST_POLLFDS);
    _ST_POLLFDS = (struct pollfd *) malloc((_ST_OSFD_CNT + 10) *
					   sizeof(struct pollfd));
    ST_ASSERT(_ST_POLLFDS != NULL);
    _ST_POLLFDS_SIZE = _ST_OSFD_CNT + 10;
  }
  pollfds = _ST_POLLFDS;

  /* Gather all descriptors into one array */
  for (q = _ST_IOQ.next; q != &_ST_IOQ; q = q->next) {
    pq = _ST_POLLQUEUE_PTR(q);
    memcpy(pollfds, pq->pds, sizeof(struct pollfd) * pq->npds);
    pollfds += pq->npds;
  }
  ST_ASSERT(pollfds <= _ST_POLLFDS + _ST_POLLFDS_SIZE);

  if (_ST_SLEEPQ == NULL) {
    timeout = -1;
  } else {
    if (_ST_SLEEPQ->due <= _st_this_vp.last_clock)
      min_timeout = 0;
    else
      min_timeout = _ST_SLEEPQ->due - _st_this_vp.last_clock;
    timeout = (int) (min_timeout / 1000);
  }

  /* Check for I/O operations */
  nfd = poll(_ST_POLLFDS, _ST_OSFD_CNT, timeout);

  /* Notify threads that are associated with the selected descriptors */
  if (nfd > 0) {
    pollfds = _ST_POLLFDS;
    for (q = _ST_IOQ.next; q != &_ST_IOQ; q = q->next) {
      pq = _ST_POLLQUEUE_PTR(q);
      epds = pollfds + pq->npds;
      for (pds = pollfds; pds < epds; pds++)
	if (pds->revents && pds->fd >= 0)   /* poll ignores negative fd's */
	  break;
      if (pds < epds) {
	memcpy(pq->pds, pollfds, sizeof(struct pollfd) * pq->npds);
        ST_REMOVE_LINK(&pq->links);
        pq->on_ioq = 0;

        if (pq->thread->flags & _ST_FL_ON_SLEEPQ)
          _ST_DEL_SLEEPQ(pq->thread);
        pq->thread->state = _ST_ST_RUNNABLE;
        _ST_ADD_RUNQ(pq->thread);

	_ST_OSFD_CNT -= pq->npds;
	ST_ASSERT(_ST_OSFD_CNT >= 0);
      }
      pollfds = epds;
    }
  }
}

#endif  /* !USE_POLL */


void st_thread_exit(void *retval)
{
  _st_thread_t *thread = _ST_CURRENT_THREAD();

  thread->retval = retval;
  _st_thread_cleanup(thread);
  _st_active_count--;
  if (thread->term) {
    /* Put thread on the zombie queue */
    thread->state = _ST_ST_ZOMBIE;
    _ST_ADD_ZOMBIEQ(thread);

    /* Notify on our termination condition variable */
    st_cond_signal(thread->term);

    /* Switch context and come back later */
    _ST_SWITCH_CONTEXT(thread);

    /* Continue the cleanup */
    st_cond_destroy(thread->term);
    thread->term = NULL;
  }

#ifdef DEBUG
  _ST_DEL_THREADQ(thread);
#endif

  if (!(thread->flags & _ST_FL_PRIMORDIAL))
    _st_stack_free(thread->stack);

  /* Find another thread to run */
  _ST_SWITCH_CONTEXT(thread);
  /* Not going to land here */
}


int st_thread_join(_st_thread_t *thread, void **retvalp)
{
  _st_cond_t *term = thread->term;

  /* Can't join a non-joinable thread */
  if (term == NULL) {
    errno = EINVAL;
    return -1;
  }
  if (_ST_CURRENT_THREAD() == thread) {
    errno = EDEADLK;
    return -1;
  }

  /* Multiple threads can't wait on the same joinable thread */
  if (term->wait_q.next != &term->wait_q) {
    errno = EINVAL;
    return -1;
  }

  while (thread->state != _ST_ST_ZOMBIE) {
    if (st_cond_timedwait(term, ST_UTIME_NO_TIMEOUT) != 0)
      return -1;
  }

  if (retvalp)
    *retvalp = thread->retval;

  /*
   * Remove target thread from the zombie queue and make it runnable.
   * When it gets scheduled later, it will do the clean up.
   */
  thread->state = _ST_ST_RUNNABLE;
  _ST_DEL_ZOMBIEQ(thread);
  _ST_ADD_RUNQ(thread);

  return 0;
}


void _st_thread_main(void)
{
  _st_thread_t *thread = _ST_CURRENT_THREAD();

  /*
   * Cap the stack by zeroing out the saved return address register
   * value. This allows some debugging/profiling tools to know when
   * to stop unwinding the stack. It's a no-op on most platforms.
   */
  MD_CAP_STACK(&thread);

  /* Run thread main */
  thread->retval = (*thread->start)(thread->arg);

  /* All done, time to go away */
  st_thread_exit(thread->retval);
}


/*
 * Insert "thread" into the timeout heap, in the position
 * specified by thread->heap_index.  See docs/timeout_heap.txt
 * for details about the timeout heap.
 */
static _st_thread_t **heap_insert(_st_thread_t *thread) {
  int target = thread->heap_index;
  int s = target;
  _st_thread_t **p = &_ST_SLEEPQ;
  int bits = 0;
  int bit;
  int index = 1;

  while (s) {
    s >>= 1;
    bits++;
  }
  for (bit = bits - 2; bit >= 0; bit--) {
    if (thread->due < (*p)->due) {
      _st_thread_t *t = *p;
      thread->left = t->left;
      thread->right = t->right;
      *p = thread;
      thread->heap_index = index;
      thread = t;
    }
    index <<= 1;
    if (target & (1 << bit)) {
      p = &((*p)->right);
      index |= 1;
    } else {
      p = &((*p)->left);
    }
  }
  thread->heap_index = index;
  *p = thread;
  thread->left = thread->right = NULL;
  return p;
}

/*
 * Delete "thread" from the timeout heap.
 */
static void heap_delete(_st_thread_t *thread) {
  _st_thread_t *t, **p;
  int bits = 0;
  int s, bit;

  /* First find and unlink the last heap element */
  p = &_ST_SLEEPQ;
  s = _ST_SLEEPQ_SIZE;
  while (s) {
    s >>= 1;
    bits++;
  }
  for (bit = bits - 2; bit >= 0; bit--) {
    if (_ST_SLEEPQ_SIZE & (1 << bit)) {
      p = &((*p)->right);
    } else {
      p = &((*p)->left);
    }
  }
  t = *p;
  *p = NULL;
  --_ST_SLEEPQ_SIZE;
  if (t != thread) {
    /*
     * Insert the unlinked last element in place of the element we are deleting
     */
    t->heap_index = thread->heap_index;
    p = heap_insert(t);
    t = *p;
    t->left = thread->left;
    t->right = thread->right;

    /*
     * Reestablish the heap invariant.
     */
    for (;;) {
      _st_thread_t *y; /* The younger child */
      int index_tmp;
      if (t->left == NULL)
	break;
      else if (t->right == NULL)
	y = t->left;
      else if (t->left->due < t->right->due)
	y = t->left;
      else
	y = t->right;
      if (t->due > y->due) {
	_st_thread_t *tl = y->left;
	_st_thread_t *tr = y->right;
	*p = y;
	if (y == t->left) {
	  y->left = t;
	  y->right = t->right;
	  p = &y->left;
	} else {
	  y->left = t->left;
	  y->right = t;
	  p = &y->right;
	}
	t->left = tl;
	t->right = tr;
	index_tmp = t->heap_index;
	t->heap_index = y->heap_index;
	y->heap_index = index_tmp;
      } else {
	break;
      }
    }
  }
  thread->left = thread->right = NULL;
}


void _st_add_sleep_q(_st_thread_t *thread, st_utime_t timeout)
{
  thread->due = _ST_LAST_CLOCK + timeout;
  thread->flags |= _ST_FL_ON_SLEEPQ;
  thread->heap_index = ++_ST_SLEEPQ_SIZE;
  heap_insert(thread);
}


void _st_del_sleep_q(_st_thread_t *thread)
{
  heap_delete(thread);
  thread->flags &= ~_ST_FL_ON_SLEEPQ;
}


void _st_vp_check_clock(void)
{
  _st_thread_t *thread;
  st_utime_t elapsed, now;
 
  now = st_utime();
  elapsed = now - _ST_LAST_CLOCK;
  _ST_LAST_CLOCK = now;

  if (_st_curr_time && now - _st_last_tset > 999000) {
    _st_curr_time = time(NULL);
    _st_last_tset = now;
  }

  while (_ST_SLEEPQ != NULL) {
    thread = _ST_SLEEPQ;
    ST_ASSERT(thread->flags & _ST_FL_ON_SLEEPQ);
    if (thread->due > now)
      break;
    _ST_DEL_SLEEPQ(thread);

    /* If thread is waiting on condition variable, set the time out flag */
    if (thread->state == _ST_ST_COND_WAIT)
      thread->flags |= _ST_FL_TIMEDOUT;

    /* Make thread runnable */
    ST_ASSERT(!(thread->flags & _ST_FL_IDLE_THREAD));
    thread->state = _ST_ST_RUNNABLE;
    _ST_ADD_RUNQ(thread);
  }
}


void st_thread_interrupt(_st_thread_t *thread)
{
  /* If thread is already dead */
  if (thread->state == _ST_ST_ZOMBIE)
    return;

  thread->flags |= _ST_FL_INTERRUPT;

  if (thread->state == _ST_ST_RUNNING || thread->state == _ST_ST_RUNNABLE)
    return;

  if (thread->flags & _ST_FL_ON_SLEEPQ)
    _ST_DEL_SLEEPQ(thread);

  /* Make thread runnable */
  thread->state = _ST_ST_RUNNABLE;
  _ST_ADD_RUNQ(thread);
}


_st_thread_t *st_thread_create(void *(*start)(void *arg), void *arg,
			       int joinable, int stk_size)
{
  _st_thread_t *thread;
  _st_stack_t *stack;
  void **ptds;
  char *sp;
#ifdef __ia64__
  char *bsp;
#endif

  /* Adjust stack size */
  if (stk_size == 0)
    stk_size = ST_DEFAULT_STACK_SIZE;
  stk_size = ((stk_size + _ST_PAGE_SIZE - 1) / _ST_PAGE_SIZE) * _ST_PAGE_SIZE;
  stack = _st_stack_new(stk_size);
  if (!stack)
    return NULL;

  /* Allocate thread object and per-thread data off the stack */
#if defined (MD_STACK_GROWS_DOWN)
  sp = stack->stk_top;
#ifdef __ia64__
  /*
   * The stack segment is split in the middle. The upper half is used
   * as backing store for the register stack which grows upward.
   * The lower half is used for the traditional memory stack which
   * grows downward. Both stacks start in the middle and grow outward
   * from each other.
   */
  sp -= (stk_size >> 1);
  bsp = sp;
  /* Make register stack 64-byte aligned */
  if ((unsigned long)bsp & 0x3f)
    bsp = bsp + (0x40 - ((unsigned long)bsp & 0x3f));
  stack->bsp = bsp + _ST_STACK_PAD_SIZE;
#endif
  sp = sp - (ST_KEYS_MAX * sizeof(void *));
  ptds = (void **) sp;
  sp = sp - sizeof(_st_thread_t);
  thread = (_st_thread_t *) sp;

  /* Make stack 64-byte aligned */
  if ((unsigned long)sp & 0x3f)
    sp = sp - ((unsigned long)sp & 0x3f);
  stack->sp = sp - _ST_STACK_PAD_SIZE;
#elif defined (MD_STACK_GROWS_UP)
  sp = stack->stk_bottom;
  thread = (_st_thread_t *) sp;
  sp = sp + sizeof(_st_thread_t);
  ptds = (void **) sp;
  sp = sp + (ST_KEYS_MAX * sizeof(void *));

  /* Make stack 64-byte aligned */
  if ((unsigned long)sp & 0x3f)
    sp = sp + (0x40 - ((unsigned long)sp & 0x3f));
  stack->sp = sp + _ST_STACK_PAD_SIZE;
#else
#error Unknown OS
#endif

  memset(thread, 0, sizeof(_st_thread_t));
  memset(ptds, 0, ST_KEYS_MAX * sizeof(void *));

  /* Initialize thread */
  thread->private_data = ptds;
  thread->stack = stack;
  thread->start = start;
  thread->arg = arg;

#ifndef __ia64__
  _ST_INIT_CONTEXT(thread, stack->sp, _st_thread_main);
#else
  _ST_INIT_CONTEXT(thread, stack->sp, stack->bsp, _st_thread_main);
#endif

  /* If thread is joinable, allocate a termination condition variable */
  if (joinable) {
    thread->term = st_cond_new();
    if (thread->term == NULL) {
      _st_stack_free(thread->stack);
      return NULL;
    }
  }

  /* Make thread runnable */
  thread->state = _ST_ST_RUNNABLE;
  _st_active_count++;
  _ST_ADD_RUNQ(thread);
#ifdef DEBUG
  _ST_ADD_THREADQ(thread);
#endif

  return thread;
}


_st_thread_t *st_thread_self(void)
{
  return _ST_CURRENT_THREAD();
}


#ifdef DEBUG
/* ARGSUSED */
void _st_show_thread_stack(_st_thread_t *thread, const char *messg)
{

}

/* To be set from debugger */
int _st_iterate_threads_flag = 0;

void _st_iterate_threads(void)
{
  static _st_thread_t *thread = NULL;
  static jmp_buf orig_jb, save_jb;
  _st_clist_t *q;

  if (!_st_iterate_threads_flag) {
    if (thread) {
      memcpy(thread->context, save_jb, sizeof(jmp_buf));
      MD_LONGJMP(orig_jb, 1);
    }
    return;
  }

  if (thread) {
    memcpy(thread->context, save_jb, sizeof(jmp_buf));
    _st_show_thread_stack(thread, NULL);
  } else {
    if (MD_SETJMP(orig_jb)) {
      _st_iterate_threads_flag = 0;
      thread = NULL;
      _st_show_thread_stack(thread, "Iteration completed");
      return;
    }
    thread = _ST_CURRENT_THREAD();
    _st_show_thread_stack(thread, "Iteration started");
  }

  q = thread->tlink.next;
  if (q == &_ST_THREADQ)
    q = q->next;
  ST_ASSERT(q != &_ST_THREADQ);
  thread = _ST_THREAD_THREADQ_PTR(q);
  if (thread == _ST_CURRENT_THREAD())
    MD_LONGJMP(orig_jb, 1);
  memcpy(save_jb, thread->context, sizeof(jmp_buf));
  MD_LONGJMP(thread->context, 1);
}
#endif /* DEBUG */