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/* Copyright (C) 2008, 2009, 2011 Free Software Foundation, Inc.

   Contributed by Jakub Jelinek <jakub@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 mutex synchronization

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

   implementation uses atomic instructions and the futex syscall.  */

#include <endian.h>

#include <limits.h>

#include "wait.h"

void *

gomp_ptrlock_get_slow (gomp_ptrlock_t *ptrlock)

{

  int *intptr;

  uintptr_t oldval = 1;

  __atomic_compare_exchange_n (ptrlock, &oldval, 2, false,

                               MEMMODEL_RELAXED, MEMMODEL_RELAXED);

  /* futex works on ints, not pointers.

     But a valid work share pointer will be at least

     8 byte aligned, so it is safe to assume the low

     32-bits of the pointer won't contain values 1 or 2.  */

  __asm volatile ("" : "=r" (intptr) : "0" (ptrlock));

#if __BYTE_ORDER == __BIG_ENDIAN

  if (sizeof (*ptrlock) > sizeof (int))

    intptr += (sizeof (*ptrlock) / sizeof (int)) - 1;

#endif

  do

    do_wait (intptr, 2);

  while (*intptr == 2);

  __asm volatile ("" : : : "memory");

  return *ptrlock;

}

void

gomp_ptrlock_set_slow (gomp_ptrlock_t *ptrlock)

{

  int *intptr;

  __asm volatile ("" : "=r" (intptr) : "0" (ptrlock));

#if __BYTE_ORDER == __BIG_ENDIAN

  if (sizeof (*ptrlock) > sizeof (int))

    intptr += (sizeof (*ptrlock) / sizeof (int)) - 1;

#endif

  futex_wake (intptr, INT_MAX);

}