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99dee823 | 1 | /* Copyright (C) 2015-2021 Free Software Foundation, Inc. |
fa499995 AS |
2 | Contributed by Mentor Embedded. |
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 AMD GCN specific implementation of a barrier synchronization | |
27 | mechanism for libgomp. This type is private to the library. This | |
28 | implementation uses atomic instructions and s_barrier instruction. It | |
29 | uses MEMMODEL_RELAXED here because barriers are within workgroups and | |
30 | therefore don't need to flush caches. */ | |
31 | ||
32 | #include <limits.h> | |
33 | #include "libgomp.h" | |
34 | ||
35 | ||
36 | void | |
37 | gomp_barrier_wait_end (gomp_barrier_t *bar, gomp_barrier_state_t state) | |
38 | { | |
39 | if (__builtin_expect (state & BAR_WAS_LAST, 0)) | |
40 | { | |
41 | /* Next time we'll be awaiting TOTAL threads again. */ | |
42 | bar->awaited = bar->total; | |
43 | __atomic_store_n (&bar->generation, bar->generation + BAR_INCR, | |
44 | MEMMODEL_RELAXED); | |
45 | } | |
6f513951 AS |
46 | if (bar->total > 1) |
47 | asm ("s_barrier" ::: "memory"); | |
fa499995 AS |
48 | } |
49 | ||
50 | void | |
51 | gomp_barrier_wait (gomp_barrier_t *bar) | |
52 | { | |
53 | gomp_barrier_wait_end (bar, gomp_barrier_wait_start (bar)); | |
54 | } | |
55 | ||
56 | /* Like gomp_barrier_wait, except that if the encountering thread | |
57 | is not the last one to hit the barrier, it returns immediately. | |
58 | The intended usage is that a thread which intends to gomp_barrier_destroy | |
59 | this barrier calls gomp_barrier_wait, while all other threads | |
60 | call gomp_barrier_wait_last. When gomp_barrier_wait returns, | |
61 | the barrier can be safely destroyed. */ | |
62 | ||
63 | void | |
64 | gomp_barrier_wait_last (gomp_barrier_t *bar) | |
65 | { | |
66 | /* Deferring to gomp_barrier_wait does not use the optimization opportunity | |
67 | allowed by the interface contract for all-but-last participants. The | |
68 | original implementation in config/linux/bar.c handles this better. */ | |
69 | gomp_barrier_wait (bar); | |
70 | } | |
71 | ||
72 | void | |
73 | gomp_team_barrier_wake (gomp_barrier_t *bar, int count) | |
74 | { | |
6f513951 AS |
75 | if (bar->total > 1) |
76 | asm ("s_barrier" ::: "memory"); | |
fa499995 AS |
77 | } |
78 | ||
79 | void | |
80 | gomp_team_barrier_wait_end (gomp_barrier_t *bar, gomp_barrier_state_t state) | |
81 | { | |
82 | unsigned int generation, gen; | |
83 | ||
84 | if (__builtin_expect (state & BAR_WAS_LAST, 0)) | |
85 | { | |
86 | /* Next time we'll be awaiting TOTAL threads again. */ | |
87 | struct gomp_thread *thr = gomp_thread (); | |
88 | struct gomp_team *team = thr->ts.team; | |
89 | ||
90 | bar->awaited = bar->total; | |
91 | team->work_share_cancelled = 0; | |
92 | if (__builtin_expect (team->task_count, 0)) | |
93 | { | |
94 | gomp_barrier_handle_tasks (state); | |
95 | state &= ~BAR_WAS_LAST; | |
96 | } | |
97 | else | |
98 | { | |
99 | state &= ~BAR_CANCELLED; | |
100 | state += BAR_INCR - BAR_WAS_LAST; | |
101 | __atomic_store_n (&bar->generation, state, MEMMODEL_RELAXED); | |
6f513951 AS |
102 | if (bar->total > 1) |
103 | asm ("s_barrier" ::: "memory"); | |
fa499995 AS |
104 | return; |
105 | } | |
106 | } | |
107 | ||
108 | generation = state; | |
109 | state &= ~BAR_CANCELLED; | |
110 | int retry = 100; | |
111 | do | |
112 | { | |
113 | if (retry-- == 0) | |
114 | { | |
115 | /* It really shouldn't happen that barriers get out of sync, but | |
116 | if they do then this will loop until they realign, so we need | |
117 | to avoid an infinite loop where the thread just isn't there. */ | |
118 | const char msg[] = ("Barrier sync failed (another thread died?);" | |
119 | " aborting."); | |
120 | write (2, msg, sizeof (msg)-1); | |
121 | abort(); | |
122 | } | |
123 | ||
124 | asm ("s_barrier" ::: "memory"); | |
125 | gen = __atomic_load_n (&bar->generation, MEMMODEL_ACQUIRE); | |
126 | if (__builtin_expect (gen & BAR_TASK_PENDING, 0)) | |
127 | { | |
128 | gomp_barrier_handle_tasks (state); | |
129 | gen = __atomic_load_n (&bar->generation, MEMMODEL_ACQUIRE); | |
130 | } | |
131 | generation |= gen & BAR_WAITING_FOR_TASK; | |
132 | } | |
133 | while (gen != state + BAR_INCR); | |
134 | } | |
135 | ||
136 | void | |
137 | gomp_team_barrier_wait (gomp_barrier_t *bar) | |
138 | { | |
139 | gomp_team_barrier_wait_end (bar, gomp_barrier_wait_start (bar)); | |
140 | } | |
141 | ||
142 | void | |
143 | gomp_team_barrier_wait_final (gomp_barrier_t *bar) | |
144 | { | |
145 | gomp_barrier_state_t state = gomp_barrier_wait_final_start (bar); | |
146 | if (__builtin_expect (state & BAR_WAS_LAST, 0)) | |
147 | bar->awaited_final = bar->total; | |
148 | gomp_team_barrier_wait_end (bar, state); | |
149 | } | |
150 | ||
151 | bool | |
152 | gomp_team_barrier_wait_cancel_end (gomp_barrier_t *bar, | |
153 | gomp_barrier_state_t state) | |
154 | { | |
155 | unsigned int generation, gen; | |
156 | ||
157 | if (__builtin_expect (state & BAR_WAS_LAST, 0)) | |
158 | { | |
159 | /* Next time we'll be awaiting TOTAL threads again. */ | |
160 | /* BAR_CANCELLED should never be set in state here, because | |
161 | cancellation means that at least one of the threads has been | |
162 | cancelled, thus on a cancellable barrier we should never see | |
163 | all threads to arrive. */ | |
164 | struct gomp_thread *thr = gomp_thread (); | |
165 | struct gomp_team *team = thr->ts.team; | |
166 | ||
167 | bar->awaited = bar->total; | |
168 | team->work_share_cancelled = 0; | |
169 | if (__builtin_expect (team->task_count, 0)) | |
170 | { | |
171 | gomp_barrier_handle_tasks (state); | |
172 | state &= ~BAR_WAS_LAST; | |
173 | } | |
174 | else | |
175 | { | |
176 | state += BAR_INCR - BAR_WAS_LAST; | |
177 | __atomic_store_n (&bar->generation, state, MEMMODEL_RELAXED); | |
6f513951 AS |
178 | if (bar->total > 1) |
179 | asm ("s_barrier" ::: "memory"); | |
fa499995 AS |
180 | return false; |
181 | } | |
182 | } | |
183 | ||
184 | if (__builtin_expect (state & BAR_CANCELLED, 0)) | |
185 | return true; | |
186 | ||
187 | generation = state; | |
188 | int retry = 100; | |
189 | do | |
190 | { | |
191 | if (retry-- == 0) | |
192 | { | |
193 | /* It really shouldn't happen that barriers get out of sync, but | |
194 | if they do then this will loop until they realign, so we need | |
195 | to avoid an infinite loop where the thread just isn't there. */ | |
196 | const char msg[] = ("Barrier sync failed (another thread died?);" | |
197 | " aborting."); | |
198 | write (2, msg, sizeof (msg)-1); | |
199 | abort(); | |
200 | } | |
201 | ||
6f513951 AS |
202 | if (bar->total > 1) |
203 | asm ("s_barrier" ::: "memory"); | |
fa499995 AS |
204 | gen = __atomic_load_n (&bar->generation, MEMMODEL_RELAXED); |
205 | if (__builtin_expect (gen & BAR_CANCELLED, 0)) | |
206 | return true; | |
207 | if (__builtin_expect (gen & BAR_TASK_PENDING, 0)) | |
208 | { | |
209 | gomp_barrier_handle_tasks (state); | |
210 | gen = __atomic_load_n (&bar->generation, MEMMODEL_RELAXED); | |
211 | } | |
212 | generation |= gen & BAR_WAITING_FOR_TASK; | |
213 | } | |
214 | while (gen != state + BAR_INCR); | |
215 | ||
216 | return false; | |
217 | } | |
218 | ||
219 | bool | |
220 | gomp_team_barrier_wait_cancel (gomp_barrier_t *bar) | |
221 | { | |
222 | return gomp_team_barrier_wait_cancel_end (bar, gomp_barrier_wait_start (bar)); | |
223 | } | |
224 | ||
225 | void | |
226 | gomp_team_barrier_cancel (struct gomp_team *team) | |
227 | { | |
228 | gomp_mutex_lock (&team->task_lock); | |
229 | if (team->barrier.generation & BAR_CANCELLED) | |
230 | { | |
231 | gomp_mutex_unlock (&team->task_lock); | |
232 | return; | |
233 | } | |
234 | team->barrier.generation |= BAR_CANCELLED; | |
235 | gomp_mutex_unlock (&team->task_lock); | |
236 | gomp_team_barrier_wake (&team->barrier, INT_MAX); | |
237 | } |