1/* Copyright (C) 2005-2015 Free Software Foundation, Inc.
2   Contributed by Richard Henderson <rth@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 file handles the CRITICAL construct.  */
27
28#include "libgomp.h"
29#include <stdlib.h>
30
31
32static gomp_mutex_t default_lock;
33
34void
35GOMP_critical_start (void)
36{
37  /* There is an implicit flush on entry to a critical region. */
38  __atomic_thread_fence (MEMMODEL_RELEASE);
39  gomp_mutex_lock (&default_lock);
40}
41
42void
43GOMP_critical_end (void)
44{
45  gomp_mutex_unlock (&default_lock);
46}
47
48#ifndef HAVE_SYNC_BUILTINS
49static gomp_mutex_t create_lock_lock;
50#endif
51
52void
53GOMP_critical_name_start (void **pptr)
54{
55  gomp_mutex_t *plock;
56
57  /* If a mutex fits within the space for a pointer, and is zero initialized,
58     then use the pointer space directly.  */
59  if (GOMP_MUTEX_INIT_0
60      && sizeof (gomp_mutex_t) <= sizeof (void *)
61      && __alignof (gomp_mutex_t) <= sizeof (void *))
62    plock = (gomp_mutex_t *)pptr;
63
64  /* Otherwise we have to be prepared to malloc storage.  */
65  else
66    {
67      plock = *pptr;
68
69      if (plock == NULL)
70	{
71#ifdef HAVE_SYNC_BUILTINS
72	  gomp_mutex_t *nlock = gomp_malloc (sizeof (gomp_mutex_t));
73	  gomp_mutex_init (nlock);
74
75	  plock = __sync_val_compare_and_swap (pptr, NULL, nlock);
76	  if (plock != NULL)
77	    {
78	      gomp_mutex_destroy (nlock);
79	      free (nlock);
80	    }
81	  else
82	    plock = nlock;
83#else
84	  gomp_mutex_lock (&create_lock_lock);
85	  plock = *pptr;
86	  if (plock == NULL)
87	    {
88	      plock = gomp_malloc (sizeof (gomp_mutex_t));
89	      gomp_mutex_init (plock);
90	      __sync_synchronize ();
91	      *pptr = plock;
92	    }
93	  gomp_mutex_unlock (&create_lock_lock);
94#endif
95	}
96    }
97
98  gomp_mutex_lock (plock);
99}
100
101void
102GOMP_critical_name_end (void **pptr)
103{
104  gomp_mutex_t *plock;
105
106  /* If a mutex fits within the space for a pointer, and is zero initialized,
107     then use the pointer space directly.  */
108  if (GOMP_MUTEX_INIT_0
109      && sizeof (gomp_mutex_t) <= sizeof (void *)
110      && __alignof (gomp_mutex_t) <= sizeof (void *))
111    plock = (gomp_mutex_t *)pptr;
112  else
113    plock = *pptr;
114
115  gomp_mutex_unlock (plock);
116}
117
118/* This mutex is used when atomic operations don't exist for the target
119   in the mode requested.  The result is not globally atomic, but works so
120   long as all parallel references are within #pragma omp atomic directives.
121   According to responses received from omp@openmp.org, appears to be within
122   spec.  Which makes sense, since that's how several other compilers
123   handle this situation as well.  */
124
125static gomp_mutex_t atomic_lock;
126
127void
128GOMP_atomic_start (void)
129{
130  gomp_mutex_lock (&atomic_lock);
131}
132
133void
134GOMP_atomic_end (void)
135{
136  gomp_mutex_unlock (&atomic_lock);
137}
138
139#if !GOMP_MUTEX_INIT_0
140static void __attribute__((constructor))
141initialize_critical (void)
142{
143  gomp_mutex_init (&default_lock);
144  gomp_mutex_init (&atomic_lock);
145#ifndef HAVE_SYNC_BUILTINS
146  gomp_mutex_init (&create_lock_lock);
147#endif
148}
149#endif
150