summaryrefslogtreecommitdiff
path: root/barrier.c
blob: e989095609440faec945649b459063f7c5f4bc17 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
/*
 * barrier.c
 *
 * Description:
 * This translation unit implements barrier primitives.
 *
 * Pthreads-win32 - POSIX Threads Library for Win32
 * Copyright (C) 1998
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Library General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Library General Public License for more details.
 *
 * You should have received a copy of the GNU Library General Public
 * License along with this library; if not, write to the Free
 * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
 * MA 02111-1307, USA
 */

#include "pthread.h"
#include "implement.h"


int
pthread_barrier_init(pthread_barrier_t * barrier,
                     const pthread_barrierattr_t * attr,
                     unsigned int count)
{
  pthread_barrier_t b;

  if (barrier == NULL || count == 0)
    {
      return EINVAL;
    }

  if (NULL != (b = (pthread_barrier_t) calloc(1, sizeof(*b))))
    {
      b->pshared = (attr != NULL && *attr != NULL
                    ? (*attr)->pshared
                    : PTHREAD_PROCESS_PRIVATE);

      b->nCurrentBarrierHeight = b->nInitialBarrierHeight = count;
      b->iStep = 0;

      /*
       * Two semaphores are used in the same way as two stepping
       * stones might be used in crossing a stream. Once all
       * threads are safely on one stone, the other stone can
       * be moved ahead, and the threads can start moving to it.
       * If some threads decide to eat their lunch before moving
       * then the other threads have to wait.
       */
      if (0 == sem_init(&(b->semBarrierBreeched[0]), b->pshared, 0))
        {
          if (0 == sem_init(&(b->semBarrierBreeched[1]), b->pshared, 0))
            {
              *barrier = b;
              return 0;
            }
          (void) sem_destroy(&(b->semBarrierBreeched[0]));
        }
      (void) free(b);
    }

  return ENOMEM;
}

int
pthread_barrier_destroy(pthread_barrier_t *barrier)
{
  int result = 0;
  pthread_barrier_t b;

  if (barrier == NULL || *barrier == (pthread_barrier_t) PTW32_OBJECT_INVALID)
    {
      return EINVAL;
    }

  b = *barrier;
  *barrier = NULL;

  if (0 == (result = sem_destroy(&(b->semBarrierBreeched[0]))))
    {
      if (0 == (result = sem_destroy(&(b->semBarrierBreeched[1]))))
        {
          (void) free(b);
          return 0;
        }
      (void) sem_init(&(b->semBarrierBreeched[0]),
                        b->pshared,
                        0);
    }

  *barrier = b;
  return(result);
}


int
pthread_barrier_wait(pthread_barrier_t *barrier)
{
  int result;
  int step;
  pthread_barrier_t b;

  if (barrier == NULL || *barrier == (pthread_barrier_t) PTW32_OBJECT_INVALID)
    {
      return EINVAL;
    }

  b = *barrier;
  step = b->iStep;

  if (0 == InterlockedDecrement((long *) &(b->nCurrentBarrierHeight)))
    {
      /* Must be done before posting the semaphore. */
      b->nCurrentBarrierHeight = b->nInitialBarrierHeight;

      /*
       * There is no race condition between the semaphore wait and post
       * because we are using two alternating semas and all threads have
       * entered barrier_wait and checked nCurrentBarrierHeight before this
       * barrier's sema can be posted. Any threads that have not quite
       * entered sem_wait below when the multiple_post has completed
       * will nevertheless continue through the semaphore (barrier)
       * and will not be left stranded.
       */
      result = (b->nInitialBarrierHeight > 1
                ? sem_post_multiple(&(b->semBarrierBreeched[step]),
                                    b->nInitialBarrierHeight - 1)
                : 0);
    }
  else
    {
      BOOL switchCancelState;
      int oldCancelState;
      pthread_t self = pthread_self();

      /*
       * This routine is not a cancelation point, so temporarily
       * prevent sem_wait() from being one.
       * PTHREAD_CANCEL_ASYNCHRONOUS threads can still be canceled.
       */
      switchCancelState = (self->cancelType == PTHREAD_CANCEL_DEFERRED &&
                           0 == pthread_setcancelstate(PTHREAD_CANCEL_DISABLE,
                                                       &oldCancelState));

      result = sem_wait(&(b->semBarrierBreeched[step]));

      if (switchCancelState)
        {
          (void) pthread_setcancelstate(oldCancelState, NULL);
        }
    }

  /*
   * The first thread across will be the PTHREAD_BARRIER_SERIAL_THREAD.
   * This also sets up the alternate semaphore as the next barrier.
   */
  if (0 == result)
    {
      result = ((PTW32_INTERLOCKED_LONG) step ==
                ptw32_interlocked_compare_exchange((PTW32_INTERLOCKED_LPLONG) &(b->iStep),
                                                   (PTW32_INTERLOCKED_LONG) (1L - step),
                                                   (PTW32_INTERLOCKED_LONG) step)
                ? PTHREAD_BARRIER_SERIAL_THREAD
                : 0);
    }

  return(result);
}


int
pthread_barrierattr_init (pthread_barrierattr_t * attr)
     /*
      * ------------------------------------------------------
      * DOCPUBLIC
      *      Initializes a barrier attributes object with default
      *      attributes.
      *
      * PARAMETERS
      *      attr
      *              pointer to an instance of pthread_barrierattr_t
      *
      *
      * DESCRIPTION
      *      Initializes a barrier attributes object with default
      *      attributes.
      *
      *      NOTES:
      *              1)      Used to define barrier types
      *
      * RESULTS
      *              0               successfully initialized attr,
      *              ENOMEM          insufficient memory for attr.
      *
      * ------------------------------------------------------
      */
{
  pthread_barrierattr_t ba;
  int result = 0;
 
  ba = (pthread_barrierattr_t) calloc (1, sizeof (*ba));
 
  if (ba == NULL)
    {
      result = ENOMEM;
    }
  else
    {
      ba->pshared = PTHREAD_PROCESS_PRIVATE;
    }

  *attr = ba;

  return (result);
}                               /* pthread_barrierattr_init */
 
 
int
pthread_barrierattr_destroy (pthread_barrierattr_t * attr)
     /*
      * ------------------------------------------------------
      * DOCPUBLIC
      *      Destroys a barrier attributes object. The object can
      *      no longer be used.
      *
      * PARAMETERS
      *      attr
      *              pointer to an instance of pthread_barrierattr_t
      *
      *
      * DESCRIPTION
      *      Destroys a barrier attributes object. The object can
      *      no longer be used.
      *
      *      NOTES:
      *              1)      Does not affect barrieres created using 'attr'
      *
      * RESULTS
      *              0               successfully released attr,
      *              EINVAL          'attr' is invalid.
      *
      * ------------------------------------------------------
      */
{
  int result = 0;
 
  if (attr == NULL || *attr == NULL)
    {
      result = EINVAL;
    }
  else
    {
      pthread_barrierattr_t ba = *attr;
 
      *attr = NULL;
      free (ba);
    }
 
  return (result);
}                               /* pthread_barrierattr_destroy */


int
pthread_barrierattr_getpshared (const pthread_barrierattr_t * attr,
                                int *pshared)
     /*
      * ------------------------------------------------------
      * DOCPUBLIC
      *      Determine whether barriers created with 'attr' can be
      *      shared between processes.
      *
      * PARAMETERS
      *      attr
      *              pointer to an instance of pthread_barrierattr_t
      *
      *      pshared
      *              will be set to one of:
      *
      *                      PTHREAD_PROCESS_SHARED
      *                              May be shared if in shared memory
      *
      *                      PTHREAD_PROCESS_PRIVATE
      *                              Cannot be shared.
      *
      *
      * DESCRIPTION
      *      Mutexes creatd with 'attr' can be shared between
      *      processes if pthread_barrier_t variable is allocated
      *      in memory shared by these processes.
      *      NOTES:
      *              1)      pshared barriers MUST be allocated in shared
      *                      memory.
      *              2)      The following macro is defined if shared barriers
      *                      are supported:
      *                              _POSIX_THREAD_PROCESS_SHARED
      *
      * RESULTS
      *              0               successfully retrieved attribute,
      *              EINVAL          'attr' is invalid,
      *
      * ------------------------------------------------------
      */
{
  int result;
 
  if ((attr != NULL && *attr != NULL) &&
      (pshared != NULL))
    {
      *pshared = (*attr)->pshared;
      result = 0;
    }
  else
    {
      result = EINVAL;
    }
 
  return (result);
}                               /* pthread_barrierattr_getpshared */


int
pthread_barrierattr_setpshared (pthread_barrierattr_t * attr,
                                int pshared)
     /*
      * ------------------------------------------------------
      * DOCPUBLIC
      *      Barriers created with 'attr' can be shared between
      *      processes if pthread_barrier_t variable is allocated
      *      in memory shared by these processes.
      *
      * PARAMETERS
      *      attr
      *              pointer to an instance of pthread_barrierattr_t
      *
      *      pshared
      *              must be one of:
      *
      *                      PTHREAD_PROCESS_SHARED
      *                              May be shared if in shared memory
      *
      *                      PTHREAD_PROCESS_PRIVATE
      *                              Cannot be shared.
      *
      * DESCRIPTION
      *      Mutexes creatd with 'attr' can be shared between
      *      processes if pthread_barrier_t variable is allocated
      *      in memory shared by these processes.
      *
      *      NOTES:
      *              1)      pshared barriers MUST be allocated in shared
      *                      memory.
      *
      *              2)      The following macro is defined if shared barriers
      *                      are supported:
      *                              _POSIX_THREAD_PROCESS_SHARED
      *
      * RESULTS
      *              0               successfully set attribute,
      *              EINVAL          'attr' or pshared is invalid,
      *              ENOSYS          PTHREAD_PROCESS_SHARED not supported,
      *
      * ------------------------------------------------------
      */
{
  int result;
 
  if ((attr != NULL && *attr != NULL) &&
      ((pshared == PTHREAD_PROCESS_SHARED) ||
       (pshared == PTHREAD_PROCESS_PRIVATE)))
    {
      if (pshared == PTHREAD_PROCESS_SHARED)
        {
 
#if !defined( _POSIX_THREAD_PROCESS_SHARED )
 
          result = ENOSYS;
          pshared = PTHREAD_PROCESS_PRIVATE;
 
#else
 
          result = 0;
 
#endif /* _POSIX_THREAD_PROCESS_SHARED */
 
        }
      else
        {
          result = 0;
        }
 
      (*attr)->pshared = pshared;
    }
  else
    {
      result = EINVAL;
    }
 
  return (result);
 
}                               /* pthread_barrierattr_setpshared */