wait.h revision 1.1.1.5 
1/* Copyright (C) 2008-2017 Free Software Foundation, Inc.
2   Contributed by Jakub Jelinek <jakub@redhat.com>.
3
4   This file is part of the GNU Offloading and Multi Processing Library
5   (libgomp).
6
7   Libgomp is free software; you can redistribute it and/or modify it
8   under the terms of the GNU General Public License as published by
9   the Free Software Foundation; either version 3, or (at your option)
10   any later version.
11
12   Libgomp is distributed in the hope that it will be useful, but WITHOUT ANY
13   WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
14   FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
15   more details.
16
17   Under Section 7 of GPL version 3, you are granted additional
18   permissions described in the GCC Runtime Library Exception, version
19   3.1, as published by the Free Software Foundation.
20
21   You should have received a copy of the GNU General Public License and
22   a copy of the GCC Runtime Library Exception along with this program;
23   see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
24   <http://www.gnu.org/licenses/>.  */
25
26/* This is a Linux specific implementation of a mutex synchronization
27   mechanism for libgomp.  This type is private to the library.  This
28   implementation uses atomic instructions and the futex syscall.  */
29
30#ifndef GOMP_WAIT_H
31#define GOMP_WAIT_H 1
32
33#include "libgomp.h"
34#include <errno.h>
35
36#define FUTEX_WAIT	0
37#define FUTEX_WAKE	1
38#define FUTEX_PRIVATE_FLAG	128
39
40#ifdef HAVE_ATTRIBUTE_VISIBILITY
41# pragma GCC visibility push(hidden)
42#endif
43
44extern int gomp_futex_wait, gomp_futex_wake;
45
46#include <futex.h>
47
48static inline int do_spin (int *addr, int val)
49{
50  unsigned long long i, count = gomp_spin_count_var;
51
52  if (__builtin_expect (__atomic_load_n (&gomp_managed_threads,
53                                         MEMMODEL_RELAXED)
54                        > gomp_available_cpus, 0))
55    count = gomp_throttled_spin_count_var;
56  for (i = 0; i < count; i++)
57    if (__builtin_expect (__atomic_load_n (addr, MEMMODEL_RELAXED) != val, 0))
58      return 0;
59    else
60      cpu_relax ();
61  return 1;
62}
63
64static inline void do_wait (int *addr, int val)
65{
66  if (do_spin (addr, val))
67    futex_wait (addr, val);
68}
69
70#ifdef HAVE_ATTRIBUTE_VISIBILITY
71# pragma GCC visibility pop
72#endif
73
74#endif /* GOMP_WAIT_H */
75