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/* Copyright (C) 2005, 2008, 2009, 2011 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 is a Linux specific implementation of a barrier synchronization

   mechanism for libgomp.  This type is private to the library.  This

   implementation uses atomic instructions and the futex syscall.  */

#ifndef GOMP_BARRIER_H

#define GOMP_BARRIER_H 1

#include "mutex.h"

typedef struct

{

  /* Make sure total/generation is in a mostly read cacheline, while

     awaited in a separate cacheline.  */

  unsigned total __attribute__((aligned (64)));

  unsigned generation;

  unsigned awaited __attribute__((aligned (64)));

} gomp_barrier_t;

typedef unsigned int gomp_barrier_state_t;

static inline void gomp_barrier_init (gomp_barrier_t *bar, unsigned count)

{

  bar->total = count;

  bar->awaited = count;

  bar->generation = 0;

}

static inline void gomp_barrier_reinit (gomp_barrier_t *bar, unsigned count)

{

  __atomic_add_fetch (&bar->awaited, count - bar->total, MEMMODEL_ACQ_REL);

  bar->total = count;

}

static inline void gomp_barrier_destroy (gomp_barrier_t *bar)

{

}

extern void gomp_barrier_wait (gomp_barrier_t *);

extern void gomp_barrier_wait_last (gomp_barrier_t *);

extern void gomp_barrier_wait_end (gomp_barrier_t *, gomp_barrier_state_t);

extern void gomp_team_barrier_wait (gomp_barrier_t *);

extern void gomp_team_barrier_wait_end (gomp_barrier_t *,

                                        gomp_barrier_state_t);

extern void gomp_team_barrier_wake (gomp_barrier_t *, int);

static inline gomp_barrier_state_t

gomp_barrier_wait_start (gomp_barrier_t *bar)

{

  unsigned int ret = __atomic_load_n (&bar->generation, MEMMODEL_ACQUIRE) & ~3;

  /* A memory barrier is needed before exiting from the various forms

     of gomp_barrier_wait, to satisfy OpenMP API version 3.1 section

     2.8.6 flush Construct, which says there is an implicit flush during

     a barrier region.  This is a convenient place to add the barrier,

     so we use MEMMODEL_ACQ_REL here rather than MEMMODEL_ACQUIRE.  */

  ret += __atomic_add_fetch (&bar->awaited, -1, MEMMODEL_ACQ_REL) == 0;

  return ret;

}

static inline bool

gomp_barrier_last_thread (gomp_barrier_state_t state)

{

  return state & 1;

}

/* All the inlines below must be called with team->task_lock

   held.  */

static inline void

gomp_team_barrier_set_task_pending (gomp_barrier_t *bar)

{

  bar->generation |= 1;

}

static inline void

gomp_team_barrier_clear_task_pending (gomp_barrier_t *bar)

{

  bar->generation &= ~1;

}

static inline void

gomp_team_barrier_set_waiting_for_tasks (gomp_barrier_t *bar)

{

  bar->generation |= 2;

}

static inline bool

gomp_team_barrier_waiting_for_tasks (gomp_barrier_t *bar)

{

  return (bar->generation & 2) != 0;

}

static inline void

gomp_team_barrier_done (gomp_barrier_t *bar, gomp_barrier_state_t state)

{

  bar->generation = (state & ~3) + 4;

}

#endif /* GOMP_BARRIER_H */