1/* Copyright (C) 2015-2022 Free Software Foundation, Inc.
2   Contributed by Alexander Monakov <amonakov@ispras.ru>
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 an NVPTX specific implementation of a semaphore synchronization
27   mechanism for libgomp.  This type is private to the library.  This
28   semaphore implementation uses atomic instructions and busy waiting.  */
29
30#ifndef GOMP_SEM_H
31#define GOMP_SEM_H 1
32
33typedef int gomp_sem_t;
34
35static inline void
36gomp_sem_init (gomp_sem_t *sem, int value)
37{
38  *sem = value;
39}
40
41static inline void
42gomp_sem_destroy (gomp_sem_t *sem)
43{
44}
45
46static inline void
47gomp_sem_wait (gomp_sem_t *sem)
48{
49  int count = __atomic_load_n (sem, MEMMODEL_ACQUIRE);
50  for (;;)
51    {
52      while (count == 0)
53	count = __atomic_load_n (sem, MEMMODEL_ACQUIRE);
54      if (__atomic_compare_exchange_n (sem, &count, count - 1, false,
55				       MEMMODEL_ACQUIRE, MEMMODEL_RELAXED))
56	return;
57    }
58}
59
60static inline void
61gomp_sem_post (gomp_sem_t *sem)
62{
63  (void) __atomic_add_fetch (sem, 1, MEMMODEL_RELEASE);
64}
65
66static inline int
67gomp_sem_getcount (gomp_sem_t *sem)
68{
69  int count = __atomic_load_n (sem, MEMMODEL_RELAXED);
70  if (count < 0)
71    return -1;
72  return count;
73}
74#endif /* GOMP_SEM_H */
75