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/* Copyright (C) 2005, 2008, 2009 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 General Public License as published by

   the Free Software Foundation; either version 3, 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 General Public License for

   more details.

   Under Section 7 of GPL version 3, you are granted additional

   permissions described in the GCC Runtime Library Exception, version

   3.1, as published by the Free Software Foundation.

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

   a copy of the GCC Runtime Library Exception along with this program;

   see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see

   <http://www.gnu.org/licenses/>.  */

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

   of threads.  */

#include "libgomp.h"

#include <stddef.h>

#include <stdlib.h>

#include <string.h>

/* Allocate a new work share structure, preferably from current team's

   free gomp_work_share cache.  */

static struct gomp_work_share *

alloc_work_share (struct gomp_team *team)

{

  struct gomp_work_share *ws;

  unsigned int i;

  /* This is called in a critical section.  */

  if (team->work_share_list_alloc != NULL)

    {

      ws = team->work_share_list_alloc;

      team->work_share_list_alloc = ws->next_free;

      return ws;

    }

#ifdef HAVE_SYNC_BUILTINS

  ws = team->work_share_list_free;

  /* We need atomic read from work_share_list_free,

     as free_work_share can be called concurrently.  */

  __asm ("" : "+r" (ws));

  if (ws && ws->next_free)

    {

      struct gomp_work_share *next = ws->next_free;

      ws->next_free = NULL;

      team->work_share_list_alloc = next->next_free;

      return next;

    }

#else

  gomp_mutex_lock (&team->work_share_list_free_lock);

  ws = team->work_share_list_free;

  if (ws)

    {

      team->work_share_list_alloc = ws->next_free;

      team->work_share_list_free = NULL;

      gomp_mutex_unlock (&team->work_share_list_free_lock);

      return ws;

    }

  gomp_mutex_unlock (&team->work_share_list_free_lock);

#endif

  team->work_share_chunk *= 2;

  ws = gomp_malloc (team->work_share_chunk * sizeof (struct gomp_work_share));

  ws->next_alloc = team->work_shares[0].next_alloc;

  team->work_shares[0].next_alloc = ws;

  team->work_share_list_alloc = &ws[1];

  for (i = 1; i < team->work_share_chunk - 1; i++)

    ws[i].next_free = &ws[i + 1];

  ws[i].next_free = NULL;

  return ws;

}

/* Initialize an already allocated struct gomp_work_share.

   This shouldn't touch the next_alloc field.  */

void

gomp_init_work_share (struct gomp_work_share *ws, bool ordered,

                      unsigned nthreads)

{

  gomp_mutex_init (&ws->lock);

  if (__builtin_expect (ordered, 0))

    {

#define INLINE_ORDERED_TEAM_IDS_CNT \

  ((sizeof (struct gomp_work_share) \

    - offsetof (struct gomp_work_share, inline_ordered_team_ids)) \

   / sizeof (((struct gomp_work_share *) 0)->inline_ordered_team_ids[0]))

      if (nthreads > INLINE_ORDERED_TEAM_IDS_CNT)

        ws->ordered_team_ids

          = gomp_malloc (nthreads * sizeof (*ws->ordered_team_ids));

      else

        ws->ordered_team_ids = ws->inline_ordered_team_ids;

      memset (ws->ordered_team_ids, '\0',

              nthreads * sizeof (*ws->ordered_team_ids));

      ws->ordered_num_used = 0;

      ws->ordered_owner = -1;

      ws->ordered_cur = 0;

    }

  else

    ws->ordered_team_ids = NULL;

  gomp_ptrlock_init (&ws->next_ws, NULL);

  ws->threads_completed = 0;

}

/* Do any needed destruction of gomp_work_share fields before it

   is put back into free gomp_work_share cache or freed.  */

void

gomp_fini_work_share (struct gomp_work_share *ws)

{

  gomp_mutex_destroy (&ws->lock);

  if (ws->ordered_team_ids != ws->inline_ordered_team_ids)

    free (ws->ordered_team_ids);

  gomp_ptrlock_destroy (&ws->next_ws);

}

/* Free a work share struct, if not orphaned, put it into current

   team's free gomp_work_share cache.  */

static inline void

free_work_share (struct gomp_team *team, struct gomp_work_share *ws)

{

  gomp_fini_work_share (ws);

  if (__builtin_expect (team == NULL, 0))

    free (ws);

  else

    {

      struct gomp_work_share *next_ws;

#ifdef HAVE_SYNC_BUILTINS

      do

        {

          next_ws = team->work_share_list_free;

          ws->next_free = next_ws;

        }

      while (!__sync_bool_compare_and_swap (&team->work_share_list_free,

                                            next_ws, ws));

#else

      gomp_mutex_lock (&team->work_share_list_free_lock);

      next_ws = team->work_share_list_free;

      ws->next_free = next_ws;

      team->work_share_list_free = ws;

      gomp_mutex_unlock (&team->work_share_list_free_lock);

#endif

    }

}

/* 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;

  /* Work sharing constructs can be orphaned.  */

  if (team == NULL)

    {

      ws = gomp_malloc (sizeof (*ws));

      gomp_init_work_share (ws, ordered, 1);

      thr->ts.work_share = ws;

      return ws;

    }

  ws = thr->ts.work_share;

  thr->ts.last_work_share = ws;

  ws = gomp_ptrlock_get (&ws->next_ws);

  if (ws == NULL)

    {

      /* This thread encountered a new ws first.  */

      struct gomp_work_share *ws = alloc_work_share (team);

      gomp_init_work_share (ws, ordered, team->nthreads);

      thr->ts.work_share = ws;

      return true;

    }

  else

    {

      thr->ts.work_share = ws;

      return false;

    }

}

/* 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;

  gomp_barrier_state_t bstate;

  /* Work sharing constructs can be orphaned.  */

  if (team == NULL)

    {

      free_work_share (NULL, thr->ts.work_share);

      thr->ts.work_share = NULL;

      return;

    }

  bstate = gomp_barrier_wait_start (&team->barrier);

  if (gomp_barrier_last_thread (bstate))

    {

      if (__builtin_expect (thr->ts.last_work_share != NULL, 1))

        free_work_share (team, thr->ts.last_work_share);

    }

  gomp_team_barrier_wait_end (&team->barrier, bstate);

  thr->ts.last_work_share = NULL;

}

/* 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;

  /* Work sharing constructs can be orphaned.  */

  if (team == NULL)

    {

      free_work_share (NULL, ws);

      thr->ts.work_share = NULL;

      return;

    }

  if (__builtin_expect (thr->ts.last_work_share == NULL, 0))

    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)

    free_work_share (team, thr->ts.last_work_share);

  thr->ts.last_work_share = NULL;

}