1 /* Copyright (C) 2005-2023 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 is the default implementation of a barrier synchronization mechanism
27 for libgomp. This type is private to the library. Note that we rely on
28 being able to adjust the barrier count while threads are blocked, so the
29 POSIX pthread_barrier_t won't work. */
30
31 #ifndef GOMP_BARRIER_H
32 #define GOMP_BARRIER_H 1
33
34 #include <pthread.h>
35
36 typedef struct
37 {
38 gomp_mutex_t mutex1;
39 #ifndef HAVE_SYNC_BUILTINS
40 gomp_mutex_t mutex2;
41 #endif
42 gomp_sem_t sem1;
43 gomp_sem_t sem2;
44 unsigned total;
45 unsigned arrived;
46 unsigned generation;
47 bool cancellable;
48 } gomp_barrier_t;
49
50 typedef unsigned int gomp_barrier_state_t;
51
52 /* The generation field contains a counter in the high bits, with a few
53 low bits dedicated to flags. Note that TASK_PENDING and WAS_LAST can
54 share space because WAS_LAST is never stored back to generation. */
55 #define BAR_TASK_PENDING 1
56 #define BAR_WAS_LAST 1
57 #define BAR_WAITING_FOR_TASK 2
58 #define BAR_CANCELLED 4
59 #define BAR_INCR 8
60
61 extern void gomp_barrier_init (gomp_barrier_t *, unsigned);
62 extern void gomp_barrier_reinit (gomp_barrier_t *, unsigned);
63 extern void gomp_barrier_destroy (gomp_barrier_t *);
64
65 extern void gomp_barrier_wait (gomp_barrier_t *);
66 extern void gomp_barrier_wait_end (gomp_barrier_t *, gomp_barrier_state_t);
67 extern void gomp_team_barrier_wait (gomp_barrier_t *);
68 extern void gomp_team_barrier_wait_end (gomp_barrier_t *,
69 gomp_barrier_state_t);
70 extern bool gomp_team_barrier_wait_cancel (gomp_barrier_t *);
71 extern bool gomp_team_barrier_wait_cancel_end (gomp_barrier_t *,
72 gomp_barrier_state_t);
73 extern void gomp_team_barrier_wake (gomp_barrier_t *, int);
74 struct gomp_team;
75 extern void gomp_team_barrier_cancel (struct gomp_team *);
76
77 static inline gomp_barrier_state_t
78 gomp_barrier_wait_start (gomp_barrier_t *bar)
79 {
80 unsigned int ret;
81 gomp_mutex_lock (&bar->mutex1);
82 ret = bar->generation & (-BAR_INCR | BAR_CANCELLED);
83 if (++bar->arrived == bar->total)
84 ret |= BAR_WAS_LAST;
85 return ret;
86 }
87
88 static inline gomp_barrier_state_t
89 gomp_barrier_wait_cancel_start (gomp_barrier_t *bar)
90 {
91 unsigned int ret;
92 gomp_mutex_lock (&bar->mutex1);
93 ret = bar->generation & (-BAR_INCR | BAR_CANCELLED);
94 if (ret & BAR_CANCELLED)
95 return ret;
96 if (++bar->arrived == bar->total)
97 ret |= BAR_WAS_LAST;
98 return ret;
99 }
100
101 static inline void
102 gomp_team_barrier_wait_final (gomp_barrier_t *bar)
103 {
104 gomp_team_barrier_wait (bar);
105 }
106
107 static inline bool
108 gomp_barrier_last_thread (gomp_barrier_state_t state)
109 {
110 return state & BAR_WAS_LAST;
111 }
112
113 static inline void
114 gomp_barrier_wait_last (gomp_barrier_t *bar)
115 {
116 gomp_barrier_wait (bar);
117 }
118
119 /* All the inlines below must be called with team->task_lock
120 held. */
121
122 static inline void
123 gomp_team_barrier_set_task_pending (gomp_barrier_t *bar)
124 {
125 bar->generation |= BAR_TASK_PENDING;
126 }
127
128 static inline void
129 gomp_team_barrier_clear_task_pending (gomp_barrier_t *bar)
130 {
131 bar->generation &= ~BAR_TASK_PENDING;
132 }
133
134 static inline void
135 gomp_team_barrier_set_waiting_for_tasks (gomp_barrier_t *bar)
136 {
137 bar->generation |= BAR_WAITING_FOR_TASK;
138 }
139
140 static inline bool
141 gomp_team_barrier_waiting_for_tasks (gomp_barrier_t *bar)
142 {
143 return (bar->generation & BAR_WAITING_FOR_TASK) != 0;
144 }
145
146 static inline bool
147 gomp_team_barrier_cancelled (gomp_barrier_t *bar)
148 {
149 return __builtin_expect ((bar->generation & BAR_CANCELLED) != 0, 0);
150 }
151
152 static inline void
153 gomp_team_barrier_done (gomp_barrier_t *bar, gomp_barrier_state_t state)
154 {
155 bar->generation = (state & -BAR_INCR) + BAR_INCR;
156 }
157
158 #endif /* GOMP_BARRIER_H */