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1 | /* Copyright (C) 2005 Free Software Foundation, Inc. |
2 | Contributed by Richard Henderson <rth@redhat.com>. | |
3 | ||
4 | This file is part of the GNU OpenMP Library (libgomp). | |
5 | ||
6 | Libgomp is free software; you can redistribute it and/or modify it | |
7 | under the terms of the GNU Lesser General Public License as published by | |
8 | the Free Software Foundation; either version 2.1 of the License, or | |
9 | (at your option) any later version. | |
10 | ||
11 | Libgomp is distributed in the hope that it will be useful, but WITHOUT ANY | |
12 | WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS | |
13 | FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for | |
14 | more details. | |
15 | ||
16 | You should have received a copy of the GNU Lesser General Public License | |
17 | along with libgomp; see the file COPYING.LIB. If not, write to the | |
18 | Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, | |
19 | MA 02110-1301, USA. */ | |
20 | ||
21 | /* As a special exception, if you link this library with other files, some | |
22 | of which are compiled with GCC, to produce an executable, this library | |
23 | does not by itself cause the resulting executable to be covered by the | |
24 | GNU General Public License. This exception does not however invalidate | |
25 | any other reasons why the executable file might be covered by the GNU | |
26 | General Public License. */ | |
27 | ||
28 | /* This file handles the maintainence of threads in response to team | |
29 | creation and termination. */ | |
30 | ||
31 | #include "libgomp.h" | |
32 | #include <stdlib.h> | |
33 | #include <string.h> | |
34 | ||
953ff289 DN |
35 | /* This array manages threads spawned from the top level, which will |
36 | return to the idle loop once the current PARALLEL construct ends. */ | |
37 | static struct gomp_thread **gomp_threads; | |
38 | static unsigned gomp_threads_size; | |
39 | static unsigned gomp_threads_used; | |
40 | ||
41 | /* This attribute contains PTHREAD_CREATE_DETACHED. */ | |
42 | static pthread_attr_t gomp_thread_attr; | |
43 | ||
44 | /* This barrier holds and releases threads waiting in gomp_threads. */ | |
45 | static gomp_barrier_t gomp_threads_dock; | |
46 | ||
47 | /* This is the libgomp per-thread data structure. */ | |
48 | #ifdef HAVE_TLS | |
49 | __thread struct gomp_thread gomp_tls_data; | |
50 | #else | |
51 | pthread_key_t gomp_tls_key; | |
52 | #endif | |
53 | ||
54 | ||
55 | /* This structure is used to communicate across pthread_create. */ | |
56 | ||
57 | struct gomp_thread_start_data | |
58 | { | |
59 | struct gomp_team_state ts; | |
60 | void (*fn) (void *); | |
61 | void *fn_data; | |
62 | bool nested; | |
63 | }; | |
64 | ||
65 | ||
66 | /* This function is a pthread_create entry point. This contains the idle | |
67 | loop in which a thread waits to be called up to become part of a team. */ | |
68 | ||
69 | static void * | |
70 | gomp_thread_start (void *xdata) | |
71 | { | |
72 | struct gomp_thread_start_data *data = xdata; | |
73 | struct gomp_thread *thr; | |
74 | void (*local_fn) (void *); | |
75 | void *local_data; | |
76 | ||
77 | #ifdef HAVE_TLS | |
78 | thr = &gomp_tls_data; | |
79 | #else | |
80 | struct gomp_thread local_thr; | |
81 | thr = &local_thr; | |
82 | pthread_setspecific (gomp_tls_key, thr); | |
83 | #endif | |
84 | gomp_sem_init (&thr->release, 0); | |
85 | ||
86 | /* Extract what we need from data. */ | |
87 | local_fn = data->fn; | |
88 | local_data = data->fn_data; | |
89 | thr->ts = data->ts; | |
90 | ||
91 | thr->ts.team->ordered_release[thr->ts.team_id] = &thr->release; | |
92 | ||
93 | if (data->nested) | |
94 | { | |
95 | gomp_barrier_wait (&thr->ts.team->barrier); | |
96 | local_fn (local_data); | |
97 | gomp_barrier_wait (&thr->ts.team->barrier); | |
98 | } | |
99 | else | |
100 | { | |
101 | gomp_threads[thr->ts.team_id] = thr; | |
102 | ||
103 | gomp_barrier_wait (&gomp_threads_dock); | |
104 | do | |
105 | { | |
106 | struct gomp_team *team; | |
107 | ||
108 | local_fn (local_data); | |
109 | ||
110 | /* Clear out the team and function data. This is a debugging | |
111 | signal that we're in fact back in the dock. */ | |
112 | team = thr->ts.team; | |
113 | thr->fn = NULL; | |
114 | thr->data = NULL; | |
115 | thr->ts.team = NULL; | |
116 | thr->ts.work_share = NULL; | |
117 | thr->ts.team_id = 0; | |
118 | thr->ts.work_share_generation = 0; | |
119 | thr->ts.static_trip = 0; | |
120 | ||
121 | gomp_barrier_wait (&team->barrier); | |
122 | gomp_barrier_wait (&gomp_threads_dock); | |
123 | ||
124 | local_fn = thr->fn; | |
125 | local_data = thr->data; | |
126 | } | |
127 | while (local_fn); | |
128 | } | |
129 | ||
130 | return NULL; | |
131 | } | |
132 | ||
133 | ||
134 | /* Create a new team data structure. */ | |
135 | ||
136 | static struct gomp_team * | |
137 | new_team (unsigned nthreads, struct gomp_work_share *work_share) | |
138 | { | |
139 | struct gomp_team *team; | |
140 | size_t size; | |
141 | ||
142 | size = sizeof (*team) + nthreads * sizeof (team->ordered_release[0]); | |
143 | team = gomp_malloc (size); | |
144 | gomp_mutex_init (&team->work_share_lock); | |
145 | ||
146 | team->work_shares = gomp_malloc (4 * sizeof (struct gomp_work_share *)); | |
147 | team->generation_mask = 3; | |
148 | team->oldest_live_gen = work_share == NULL; | |
149 | team->num_live_gen = work_share != NULL; | |
150 | team->work_shares[0] = work_share; | |
151 | ||
152 | team->nthreads = nthreads; | |
153 | gomp_barrier_init (&team->barrier, nthreads); | |
154 | ||
155 | gomp_sem_init (&team->master_release, 0); | |
156 | team->ordered_release[0] = &team->master_release; | |
157 | ||
158 | return team; | |
159 | } | |
160 | ||
161 | ||
162 | /* Free a team data structure. */ | |
163 | ||
164 | static void | |
165 | free_team (struct gomp_team *team) | |
166 | { | |
167 | free (team->work_shares); | |
168 | gomp_mutex_destroy (&team->work_share_lock); | |
169 | gomp_barrier_destroy (&team->barrier); | |
170 | gomp_sem_destroy (&team->master_release); | |
171 | free (team); | |
172 | } | |
173 | ||
174 | ||
175 | /* Launch a team. */ | |
176 | ||
177 | void | |
178 | gomp_team_start (void (*fn) (void *), void *data, unsigned nthreads, | |
179 | struct gomp_work_share *work_share) | |
180 | { | |
181 | struct gomp_thread_start_data *start_data; | |
182 | struct gomp_thread *thr, *nthr; | |
183 | struct gomp_team *team; | |
184 | bool nested; | |
185 | unsigned i, n, old_threads_used = 0; | |
186 | ||
187 | thr = gomp_thread (); | |
188 | nested = thr->ts.team != NULL; | |
189 | ||
190 | team = new_team (nthreads, work_share); | |
191 | ||
192 | /* Always save the previous state, even if this isn't a nested team. | |
193 | In particular, we should save any work share state from an outer | |
194 | orphaned work share construct. */ | |
195 | team->prev_ts = thr->ts; | |
196 | ||
197 | thr->ts.team = team; | |
198 | thr->ts.work_share = work_share; | |
199 | thr->ts.team_id = 0; | |
200 | thr->ts.work_share_generation = 0; | |
201 | thr->ts.static_trip = 0; | |
202 | ||
203 | if (nthreads == 1) | |
204 | return; | |
205 | ||
206 | i = 1; | |
207 | ||
208 | /* We only allow the reuse of idle threads for non-nested PARALLEL | |
209 | regions. This appears to be implied by the semantics of | |
210 | threadprivate variables, but perhaps that's reading too much into | |
211 | things. Certainly it does prevent any locking problems, since | |
212 | only the initial program thread will modify gomp_threads. */ | |
213 | if (!nested) | |
214 | { | |
215 | old_threads_used = gomp_threads_used; | |
216 | ||
217 | if (nthreads <= old_threads_used) | |
218 | n = nthreads; | |
219 | else if (old_threads_used == 0) | |
220 | { | |
221 | n = 0; | |
222 | gomp_barrier_init (&gomp_threads_dock, nthreads); | |
223 | } | |
224 | else | |
225 | { | |
226 | n = old_threads_used; | |
227 | ||
228 | /* Increase the barrier threshold to make sure all new | |
229 | threads arrive before the team is released. */ | |
230 | gomp_barrier_reinit (&gomp_threads_dock, nthreads); | |
231 | } | |
232 | ||
233 | /* Not true yet, but soon will be. We're going to release all | |
234 | threads from the dock, and those that aren't part of the | |
235 | team will exit. */ | |
236 | gomp_threads_used = nthreads; | |
237 | ||
238 | /* Release existing idle threads. */ | |
239 | for (; i < n; ++i) | |
240 | { | |
241 | nthr = gomp_threads[i]; | |
242 | nthr->ts.team = team; | |
243 | nthr->ts.work_share = work_share; | |
244 | nthr->ts.team_id = i; | |
245 | nthr->ts.work_share_generation = 0; | |
246 | nthr->ts.static_trip = 0; | |
247 | nthr->fn = fn; | |
248 | nthr->data = data; | |
249 | team->ordered_release[i] = &nthr->release; | |
250 | } | |
251 | ||
252 | if (i == nthreads) | |
253 | goto do_release; | |
254 | ||
255 | /* If necessary, expand the size of the gomp_threads array. It is | |
256 | expected that changes in the number of threads is rare, thus we | |
257 | make no effort to expand gomp_threads_size geometrically. */ | |
258 | if (nthreads >= gomp_threads_size) | |
259 | { | |
260 | gomp_threads_size = nthreads + 1; | |
261 | gomp_threads | |
262 | = gomp_realloc (gomp_threads, | |
263 | gomp_threads_size | |
264 | * sizeof (struct gomp_thread_data *)); | |
265 | } | |
266 | } | |
267 | ||
a55b8e18 SE |
268 | start_data = gomp_alloca (sizeof (struct gomp_thread_start_data) |
269 | * (nthreads-i)); | |
953ff289 DN |
270 | |
271 | /* Launch new threads. */ | |
272 | for (; i < nthreads; ++i, ++start_data) | |
273 | { | |
274 | pthread_t pt; | |
275 | int err; | |
276 | ||
277 | start_data->ts.team = team; | |
278 | start_data->ts.work_share = work_share; | |
279 | start_data->ts.team_id = i; | |
280 | start_data->ts.work_share_generation = 0; | |
281 | start_data->ts.static_trip = 0; | |
282 | start_data->fn = fn; | |
283 | start_data->fn_data = data; | |
284 | start_data->nested = nested; | |
285 | ||
286 | err = pthread_create (&pt, &gomp_thread_attr, | |
287 | gomp_thread_start, start_data); | |
288 | if (err != 0) | |
289 | gomp_fatal ("Thread creation failed: %s", strerror (err)); | |
290 | } | |
291 | ||
292 | do_release: | |
293 | gomp_barrier_wait (nested ? &team->barrier : &gomp_threads_dock); | |
294 | ||
295 | /* Decrease the barrier threshold to match the number of threads | |
296 | that should arrive back at the end of this team. The extra | |
297 | threads should be exiting. Note that we arrange for this test | |
298 | to never be true for nested teams. */ | |
299 | if (nthreads < old_threads_used) | |
300 | gomp_barrier_reinit (&gomp_threads_dock, nthreads); | |
301 | } | |
302 | ||
303 | ||
304 | /* Terminate the current team. This is only to be called by the master | |
305 | thread. We assume that we must wait for the other threads. */ | |
306 | ||
307 | void | |
308 | gomp_team_end (void) | |
309 | { | |
310 | struct gomp_thread *thr = gomp_thread (); | |
311 | struct gomp_team *team = thr->ts.team; | |
312 | ||
313 | gomp_barrier_wait (&team->barrier); | |
314 | ||
315 | thr->ts = team->prev_ts; | |
316 | ||
317 | free_team (team); | |
318 | } | |
319 | ||
320 | ||
321 | /* Constructors for this file. */ | |
322 | ||
323 | static void __attribute__((constructor)) | |
324 | initialize_team (void) | |
325 | { | |
326 | struct gomp_thread *thr; | |
327 | ||
328 | #ifndef HAVE_TLS | |
329 | static struct gomp_thread initial_thread_tls_data; | |
330 | ||
331 | pthread_key_create (&gomp_tls_key, NULL); | |
332 | pthread_setspecific (gomp_tls_key, &initial_thread_tls_data); | |
333 | #endif | |
334 | ||
335 | #ifdef HAVE_TLS | |
336 | thr = &gomp_tls_data; | |
337 | #else | |
338 | thr = &initial_thread_tls_data; | |
339 | #endif | |
340 | gomp_sem_init (&thr->release, 0); | |
341 | ||
342 | pthread_attr_init (&gomp_thread_attr); | |
343 | pthread_attr_setdetachstate (&gomp_thread_attr, PTHREAD_CREATE_DETACHED); | |
344 | } |