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/* Copyright (C) 2005 Free Software Foundation, Inc.

   Contributed by Richard Henderson <rth@redhat.com>.

   This file is part of the GNU OpenMP Library (libgomp).

   Libgomp is free software; you can redistribute it and/or modify it

   under the terms of the GNU Lesser General Public License as published by

   the Free Software Foundation; either version 2.1 of the License, or

   (at your option) any later version.

   Libgomp is distributed in the hope that it will be useful, but WITHOUT ANY

   WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS

   FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public License for

   more details.

   You should have received a copy of the GNU Lesser General Public License

   along with libgomp; see the file COPYING.LIB.  If not, write to the

   Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,

   MA 02110-1301, USA.  */

/* As a special exception, if you link this library with other files, some

   of which are compiled with GCC, to produce an executable, this library

   does not by itself cause the resulting executable to be covered by the

   GNU General Public License.  This exception does not however invalidate

   any other reasons why the executable file might be covered by the GNU

   General Public License.  */

/* This file contains routines to manage the work-share queue for a team

   of threads.  */

#include "libgomp.h"

#include <stdlib.h>

#include <string.h>

/* Create a new work share structure.  */

struct gomp_work_share *

gomp_new_work_share (bool ordered, unsigned nthreads)

{

  struct gomp_work_share *ws;

  size_t size;

  size = sizeof (*ws);

  if (ordered)

    size += nthreads * sizeof (ws->ordered_team_ids[0]);

  ws = gomp_malloc_cleared (size);

  gomp_mutex_init (&ws->lock);

  ws->ordered_owner = -1;

  return ws;

}

/* Free a work share structure.  */

static void

free_work_share (struct gomp_work_share *ws)

{

  gomp_mutex_destroy (&ws->lock);

  free (ws);

}

/* The current thread is ready to begin the next work sharing construct.

   In all cases, thr->ts.work_share is updated to point to the new

   structure.  In all cases the work_share lock is locked.  Return true

   if this was the first thread to reach this point.  */

bool

gomp_work_share_start (bool ordered)

{

  struct gomp_thread *thr = gomp_thread ();

  struct gomp_team *team = thr->ts.team;

  struct gomp_work_share *ws;

  unsigned ws_index, ws_gen;

  /* Work sharing constructs can be orphaned.  */

  if (team == NULL)

    {

      ws = gomp_new_work_share (ordered, 1);

      thr->ts.work_share = ws;

      thr->ts.static_trip = 0;

      gomp_mutex_lock (&ws->lock);

      return true;

    }

  gomp_mutex_lock (&team->work_share_lock);

  /* This thread is beginning its next generation.  */

  ws_gen = ++thr->ts.work_share_generation;

  /* If this next generation is not newer than any other generation in

     the team, then simply reference the existing construct.  */

  if (ws_gen - team->oldest_live_gen < team->num_live_gen)

    {

      ws_index = ws_gen & team->generation_mask;

      ws = team->work_shares[ws_index];

      thr->ts.work_share = ws;

      thr->ts.static_trip = 0;

      gomp_mutex_lock (&ws->lock);

      gomp_mutex_unlock (&team->work_share_lock);

      return false;

    }

  /* Resize the work shares queue if we've run out of space.  */

  if (team->num_live_gen++ == team->generation_mask)

    {

      team->work_shares = gomp_realloc (team->work_shares,

                                        2 * team->num_live_gen

                                        * sizeof (*team->work_shares));

      /* Unless oldest_live_gen is zero, the sequence of live elements

         wraps around the end of the array.  If we do nothing, we break

         lookup of the existing elements.  Fix that by unwrapping the

         data from the front to the end.  */

      if (team->oldest_live_gen > 0)

        memcpy (team->work_shares + team->num_live_gen,

                team->work_shares,

                (team->oldest_live_gen & team->generation_mask)

                * sizeof (*team->work_shares));

      team->generation_mask = team->generation_mask * 2 + 1;

    }

  ws_index = ws_gen & team->generation_mask;

  ws = gomp_new_work_share (ordered, team->nthreads);

  thr->ts.work_share = ws;

  thr->ts.static_trip = 0;

  team->work_shares[ws_index] = ws;

  gomp_mutex_lock (&ws->lock);

  gomp_mutex_unlock (&team->work_share_lock);

  return true;

}

/* The current thread is done with its current work sharing construct.

   This version does imply a barrier at the end of the work-share.  */

void

gomp_work_share_end (void)

{

  struct gomp_thread *thr = gomp_thread ();

  struct gomp_team *team = thr->ts.team;

  struct gomp_work_share *ws = thr->ts.work_share;

  bool last;

  thr->ts.work_share = NULL;

  /* Work sharing constructs can be orphaned.  */

  if (team == NULL)

    {

      free_work_share (ws);

      return;

    }

  last = gomp_barrier_wait_start (&team->barrier);

  if (last)

    {

      unsigned ws_index;

      ws_index = thr->ts.work_share_generation & team->generation_mask;

      team->work_shares[ws_index] = NULL;

      team->oldest_live_gen++;

      team->num_live_gen = 0;

      free_work_share (ws);

    }

  gomp_barrier_wait_end (&team->barrier, last);

}

/* The current thread is done with its current work sharing construct.

   This version does NOT imply a barrier at the end of the work-share.  */

void

gomp_work_share_end_nowait (void)

{

  struct gomp_thread *thr = gomp_thread ();

  struct gomp_team *team = thr->ts.team;

  struct gomp_work_share *ws = thr->ts.work_share;

  unsigned completed;

  thr->ts.work_share = NULL;

  /* Work sharing constructs can be orphaned.  */

  if (team == NULL)

    {

      free_work_share (ws);

      return;

    }

#ifdef HAVE_SYNC_BUILTINS

  completed = __sync_add_and_fetch (&ws->threads_completed, 1);

#else

  gomp_mutex_lock (&ws->lock);

  completed = ++ws->threads_completed;

  gomp_mutex_unlock (&ws->lock);

#endif

  if (completed == team->nthreads)

    {

      unsigned ws_index;

      gomp_mutex_lock (&team->work_share_lock);

      ws_index = thr->ts.work_share_generation & team->generation_mask;

      team->work_shares[ws_index] = NULL;

      team->oldest_live_gen++;

      team->num_live_gen--;

      gomp_mutex_unlock (&team->work_share_lock);

      free_work_share (ws);

    }

}