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
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
|
/* $OpenLDAP$ */
/* This work is part of OpenLDAP Software <http://www.openldap.org/>.
*
* Copyright 1998-2018 The OpenLDAP Foundation.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted only as authorized by the OpenLDAP
* Public License.
*
* A copy of this license is available in file LICENSE in the
* top-level directory of the distribution or, alternatively, at
* <http://www.OpenLDAP.org/license.html>.
*/
/* This work was initially developed by Kurt D. Zeilenga for inclusion
* in OpenLDAP Software. Additional significant contributors include:
* Stuart Lynne
*/
/*
* This is an improved implementation of Reader/Writer locks does
* not protect writers from starvation. That is, if a writer is
* currently waiting on a reader, any new reader will get
* the lock before the writer.
*
* Does not support cancellation nor does any status checking.
*/
/* Adapted from publically available examples for:
* "Programming with Posix Threads"
* by David R Butenhof, Addison-Wesley
* http://cseng.aw.com/bookpage.taf?ISBN=0-201-63392-2
*/
#include "portable.h"
#include <ac/stdlib.h>
#include <ac/errno.h>
#include <ac/string.h>
#include <ac/time.h>
#include "ldap-int.h"
#include "ldap_pvt_thread.h" /* Get the thread interface */
#define LDAP_THREAD_RDWR_IMPLEMENTATION
#include "ldap_thr_debug.h" /* May rename the symbols defined below */
/*
* implementations that provide their own compatible
* reader/writer locks define LDAP_THREAD_HAVE_RDWR
* in ldap_pvt_thread.h
*/
#ifndef LDAP_THREAD_HAVE_RDWR
struct ldap_int_thread_rdwr_s {
ldap_pvt_thread_mutex_t ltrw_mutex;
ldap_pvt_thread_cond_t ltrw_read; /* wait for read */
ldap_pvt_thread_cond_t ltrw_write; /* wait for write */
int ltrw_valid;
#define LDAP_PVT_THREAD_RDWR_VALID 0x0bad
int ltrw_r_active;
int ltrw_w_active;
int ltrw_r_wait;
int ltrw_w_wait;
#ifdef LDAP_RDWR_DEBUG
/* keep track of who has these locks */
#define MAX_READERS 32
int ltrw_more_readers; /* Set if ltrw_readers[] is incomplete */
ldap_pvt_thread_t ltrw_readers[MAX_READERS];
ldap_pvt_thread_t ltrw_writer;
#endif
};
int
ldap_pvt_thread_rdwr_init( ldap_pvt_thread_rdwr_t *rwlock )
{
struct ldap_int_thread_rdwr_s *rw;
assert( rwlock != NULL );
rw = (struct ldap_int_thread_rdwr_s *) LDAP_CALLOC( 1,
sizeof( struct ldap_int_thread_rdwr_s ) );
if ( !rw )
return LDAP_NO_MEMORY;
/* we should check return results */
ldap_pvt_thread_mutex_init( &rw->ltrw_mutex );
ldap_pvt_thread_cond_init( &rw->ltrw_read );
ldap_pvt_thread_cond_init( &rw->ltrw_write );
rw->ltrw_valid = LDAP_PVT_THREAD_RDWR_VALID;
*rwlock = rw;
return 0;
}
int
ldap_pvt_thread_rdwr_destroy( ldap_pvt_thread_rdwr_t *rwlock )
{
struct ldap_int_thread_rdwr_s *rw;
assert( rwlock != NULL );
rw = *rwlock;
assert( rw != NULL );
assert( rw->ltrw_valid == LDAP_PVT_THREAD_RDWR_VALID );
if( rw->ltrw_valid != LDAP_PVT_THREAD_RDWR_VALID )
return LDAP_PVT_THREAD_EINVAL;
ldap_pvt_thread_mutex_lock( &rw->ltrw_mutex );
assert( rw->ltrw_w_active >= 0 );
assert( rw->ltrw_w_wait >= 0 );
assert( rw->ltrw_r_active >= 0 );
assert( rw->ltrw_r_wait >= 0 );
/* active threads? */
if( rw->ltrw_r_active > 0 || rw->ltrw_w_active > 0) {
ldap_pvt_thread_mutex_unlock( &rw->ltrw_mutex );
return LDAP_PVT_THREAD_EBUSY;
}
/* waiting threads? */
if( rw->ltrw_r_wait > 0 || rw->ltrw_w_wait > 0) {
ldap_pvt_thread_mutex_unlock( &rw->ltrw_mutex );
return LDAP_PVT_THREAD_EBUSY;
}
rw->ltrw_valid = 0;
ldap_pvt_thread_mutex_unlock( &rw->ltrw_mutex );
ldap_pvt_thread_mutex_destroy( &rw->ltrw_mutex );
ldap_pvt_thread_cond_destroy( &rw->ltrw_read );
ldap_pvt_thread_cond_destroy( &rw->ltrw_write );
LDAP_FREE(rw);
*rwlock = NULL;
return 0;
}
int ldap_pvt_thread_rdwr_rlock( ldap_pvt_thread_rdwr_t *rwlock )
{
struct ldap_int_thread_rdwr_s *rw;
assert( rwlock != NULL );
rw = *rwlock;
assert( rw != NULL );
assert( rw->ltrw_valid == LDAP_PVT_THREAD_RDWR_VALID );
if( rw->ltrw_valid != LDAP_PVT_THREAD_RDWR_VALID )
return LDAP_PVT_THREAD_EINVAL;
ldap_pvt_thread_mutex_lock( &rw->ltrw_mutex );
assert( rw->ltrw_w_active >= 0 );
assert( rw->ltrw_w_wait >= 0 );
assert( rw->ltrw_r_active >= 0 );
assert( rw->ltrw_r_wait >= 0 );
if( rw->ltrw_w_active > 0 ) {
/* writer is active */
rw->ltrw_r_wait++;
do {
ldap_pvt_thread_cond_wait(
&rw->ltrw_read, &rw->ltrw_mutex );
} while( rw->ltrw_w_active > 0 );
rw->ltrw_r_wait--;
assert( rw->ltrw_r_wait >= 0 );
}
#ifdef LDAP_RDWR_DEBUG
if( rw->ltrw_r_active < MAX_READERS )
rw->ltrw_readers[rw->ltrw_r_active] = ldap_pvt_thread_self();
else
rw->ltrw_more_readers = 1;
#endif
rw->ltrw_r_active++;
ldap_pvt_thread_mutex_unlock( &rw->ltrw_mutex );
return 0;
}
int ldap_pvt_thread_rdwr_rtrylock( ldap_pvt_thread_rdwr_t *rwlock )
{
struct ldap_int_thread_rdwr_s *rw;
assert( rwlock != NULL );
rw = *rwlock;
assert( rw != NULL );
assert( rw->ltrw_valid == LDAP_PVT_THREAD_RDWR_VALID );
if( rw->ltrw_valid != LDAP_PVT_THREAD_RDWR_VALID )
return LDAP_PVT_THREAD_EINVAL;
ldap_pvt_thread_mutex_lock( &rw->ltrw_mutex );
assert( rw->ltrw_w_active >= 0 );
assert( rw->ltrw_w_wait >= 0 );
assert( rw->ltrw_r_active >= 0 );
assert( rw->ltrw_r_wait >= 0 );
if( rw->ltrw_w_active > 0) {
ldap_pvt_thread_mutex_unlock( &rw->ltrw_mutex );
return LDAP_PVT_THREAD_EBUSY;
}
#ifdef LDAP_RDWR_DEBUG
if( rw->ltrw_r_active < MAX_READERS )
rw->ltrw_readers[rw->ltrw_r_active] = ldap_pvt_thread_self();
else
rw->ltrw_more_readers = 1;
#endif
rw->ltrw_r_active++;
ldap_pvt_thread_mutex_unlock( &rw->ltrw_mutex );
return 0;
}
int ldap_pvt_thread_rdwr_runlock( ldap_pvt_thread_rdwr_t *rwlock )
{
struct ldap_int_thread_rdwr_s *rw;
assert( rwlock != NULL );
rw = *rwlock;
assert( rw != NULL );
assert( rw->ltrw_valid == LDAP_PVT_THREAD_RDWR_VALID );
if( rw->ltrw_valid != LDAP_PVT_THREAD_RDWR_VALID )
return LDAP_PVT_THREAD_EINVAL;
ldap_pvt_thread_mutex_lock( &rw->ltrw_mutex );
rw->ltrw_r_active--;
#ifdef LDAP_RDWR_DEBUG
/* Remove us from the list of readers */
{
ldap_pvt_thread_t self = ldap_pvt_thread_self();
int i, j;
for( i = j = rw->ltrw_r_active; i >= 0; i--) {
if (rw->ltrw_readers[i] == self) {
rw->ltrw_readers[i] = rw->ltrw_readers[j];
rw->ltrw_readers[j] = 0;
break;
}
}
if( !rw->ltrw_more_readers )
assert( i >= 0 );
else if( j == 0 )
rw->ltrw_more_readers = 0;
}
#endif
assert( rw->ltrw_w_active >= 0 );
assert( rw->ltrw_w_wait >= 0 );
assert( rw->ltrw_r_active >= 0 );
assert( rw->ltrw_r_wait >= 0 );
if (rw->ltrw_r_active == 0 && rw->ltrw_w_wait > 0 ) {
ldap_pvt_thread_cond_signal( &rw->ltrw_write );
}
ldap_pvt_thread_mutex_unlock( &rw->ltrw_mutex );
return 0;
}
int ldap_pvt_thread_rdwr_wlock( ldap_pvt_thread_rdwr_t *rwlock )
{
struct ldap_int_thread_rdwr_s *rw;
assert( rwlock != NULL );
rw = *rwlock;
assert( rw != NULL );
assert( rw->ltrw_valid == LDAP_PVT_THREAD_RDWR_VALID );
if( rw->ltrw_valid != LDAP_PVT_THREAD_RDWR_VALID )
return LDAP_PVT_THREAD_EINVAL;
ldap_pvt_thread_mutex_lock( &rw->ltrw_mutex );
assert( rw->ltrw_w_active >= 0 );
assert( rw->ltrw_w_wait >= 0 );
assert( rw->ltrw_r_active >= 0 );
assert( rw->ltrw_r_wait >= 0 );
if ( rw->ltrw_w_active > 0 || rw->ltrw_r_active > 0 ) {
rw->ltrw_w_wait++;
do {
ldap_pvt_thread_cond_wait(
&rw->ltrw_write, &rw->ltrw_mutex );
} while ( rw->ltrw_w_active > 0 || rw->ltrw_r_active > 0 );
rw->ltrw_w_wait--;
assert( rw->ltrw_w_wait >= 0 );
}
#ifdef LDAP_RDWR_DEBUG
rw->ltrw_writer = ldap_pvt_thread_self();
#endif
rw->ltrw_w_active++;
ldap_pvt_thread_mutex_unlock( &rw->ltrw_mutex );
return 0;
}
int ldap_pvt_thread_rdwr_wtrylock( ldap_pvt_thread_rdwr_t *rwlock )
{
struct ldap_int_thread_rdwr_s *rw;
assert( rwlock != NULL );
rw = *rwlock;
assert( rw != NULL );
assert( rw->ltrw_valid == LDAP_PVT_THREAD_RDWR_VALID );
if( rw->ltrw_valid != LDAP_PVT_THREAD_RDWR_VALID )
return LDAP_PVT_THREAD_EINVAL;
ldap_pvt_thread_mutex_lock( &rw->ltrw_mutex );
assert( rw->ltrw_w_active >= 0 );
assert( rw->ltrw_w_wait >= 0 );
assert( rw->ltrw_r_active >= 0 );
assert( rw->ltrw_r_wait >= 0 );
if ( rw->ltrw_w_active > 0 || rw->ltrw_r_active > 0 ) {
ldap_pvt_thread_mutex_unlock( &rw->ltrw_mutex );
return LDAP_PVT_THREAD_EBUSY;
}
#ifdef LDAP_RDWR_DEBUG
rw->ltrw_writer = ldap_pvt_thread_self();
#endif
rw->ltrw_w_active++;
ldap_pvt_thread_mutex_unlock( &rw->ltrw_mutex );
return 0;
}
int ldap_pvt_thread_rdwr_wunlock( ldap_pvt_thread_rdwr_t *rwlock )
{
struct ldap_int_thread_rdwr_s *rw;
assert( rwlock != NULL );
rw = *rwlock;
assert( rw != NULL );
assert( rw->ltrw_valid == LDAP_PVT_THREAD_RDWR_VALID );
if( rw->ltrw_valid != LDAP_PVT_THREAD_RDWR_VALID )
return LDAP_PVT_THREAD_EINVAL;
ldap_pvt_thread_mutex_lock( &rw->ltrw_mutex );
rw->ltrw_w_active--;
assert( rw->ltrw_w_active >= 0 );
assert( rw->ltrw_w_wait >= 0 );
assert( rw->ltrw_r_active >= 0 );
assert( rw->ltrw_r_wait >= 0 );
if (rw->ltrw_r_wait > 0) {
ldap_pvt_thread_cond_broadcast( &rw->ltrw_read );
} else if (rw->ltrw_w_wait > 0) {
ldap_pvt_thread_cond_signal( &rw->ltrw_write );
}
#ifdef LDAP_RDWR_DEBUG
assert( rw->ltrw_writer == ldap_pvt_thread_self() );
rw->ltrw_writer = 0;
#endif
ldap_pvt_thread_mutex_unlock( &rw->ltrw_mutex );
return 0;
}
#ifdef LDAP_RDWR_DEBUG
/* just for testing,
* return 0 if false, suitable for assert(ldap_pvt_thread_rdwr_Xchk(rdwr))
*
* Currently they don't check if the calling thread is the one
* that has the lock, just that there is a reader or writer.
*
* Basically sufficent for testing that places that should have
* a lock are caught.
*/
int ldap_pvt_thread_rdwr_readers(ldap_pvt_thread_rdwr_t *rwlock)
{
struct ldap_int_thread_rdwr_s *rw;
assert( rwlock != NULL );
rw = *rwlock;
assert( rw != NULL );
assert( rw->ltrw_valid == LDAP_PVT_THREAD_RDWR_VALID );
assert( rw->ltrw_w_active >= 0 );
assert( rw->ltrw_w_wait >= 0 );
assert( rw->ltrw_r_active >= 0 );
assert( rw->ltrw_r_wait >= 0 );
return( rw->ltrw_r_active );
}
int ldap_pvt_thread_rdwr_writers(ldap_pvt_thread_rdwr_t *rwlock)
{
struct ldap_int_thread_rdwr_s *rw;
assert( rwlock != NULL );
rw = *rwlock;
assert( rw != NULL );
assert( rw->ltrw_valid == LDAP_PVT_THREAD_RDWR_VALID );
assert( rw->ltrw_w_active >= 0 );
assert( rw->ltrw_w_wait >= 0 );
assert( rw->ltrw_r_active >= 0 );
assert( rw->ltrw_r_wait >= 0 );
return( rw->ltrw_w_active );
}
int ldap_pvt_thread_rdwr_active(ldap_pvt_thread_rdwr_t *rwlock)
{
struct ldap_int_thread_rdwr_s *rw;
assert( rwlock != NULL );
rw = *rwlock;
assert( rw != NULL );
assert( rw->ltrw_valid == LDAP_PVT_THREAD_RDWR_VALID );
assert( rw->ltrw_w_active >= 0 );
assert( rw->ltrw_w_wait >= 0 );
assert( rw->ltrw_r_active >= 0 );
assert( rw->ltrw_r_wait >= 0 );
return(ldap_pvt_thread_rdwr_readers(rwlock) +
ldap_pvt_thread_rdwr_writers(rwlock));
}
#endif /* LDAP_RDWR_DEBUG */
#endif /* LDAP_THREAD_HAVE_RDWR */
|
