pthread_rwlock.c revision 1.1.2.4
1 /* $NetBSD: pthread_rwlock.c,v 1.1.2.4 2003/01/09 19:27:52 thorpej Exp $ */ 2 3 /*- 4 * Copyright (c) 2002 The NetBSD Foundation, Inc. 5 * All rights reserved. 6 * 7 * This code is derived from software contributed to The NetBSD Foundation 8 * by Nathan J. Williams. 9 * 10 * Redistribution and use in source and binary forms, with or without 11 * modification, are permitted provided that the following conditions 12 * are met: 13 * 1. Redistributions of source code must retain the above copyright 14 * notice, this list of conditions and the following disclaimer. 15 * 2. Redistributions in binary form must reproduce the above copyright 16 * notice, this list of conditions and the following disclaimer in the 17 * documentation and/or other materials provided with the distribution. 18 * 3. All advertising materials mentioning features or use of this software 19 * must display the following acknowledgement: 20 * This product includes software developed by the NetBSD 21 * Foundation, Inc. and its contributors. 22 * 4. Neither the name of The NetBSD Foundation nor the names of its 23 * contributors may be used to endorse or promote products derived 24 * from this software without specific prior written permission. 25 * 26 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS 27 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 28 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 29 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS 30 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 31 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 32 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 33 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 34 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 35 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 36 * POSSIBILITY OF SUCH DAMAGE. 37 */ 38 39 #include <assert.h> 40 #include <errno.h> 41 #include <sys/cdefs.h> 42 43 #include "pthread.h" 44 #include "pthread_int.h" 45 46 static void pthread_rwlock__callback(void *); 47 48 __strong_alias(__libc_rwlock_init,pthread_rwlock_init) 49 __strong_alias(__libc_rwlock_rdlock,pthread_rwlock_rdlock) 50 __strong_alias(__libc_rwlock_wrlock,pthread_rwlock_wrlock) 51 __strong_alias(__libc_rwlock_tryrdlock,pthread_rwlock_tryrdlock) 52 __strong_alias(__libc_rwlock_trywrlock,pthread_rwlock_trywrlock) 53 __strong_alias(__libc_rwlock_unlock,pthread_rwlock_unlock) 54 __strong_alias(__libc_rwlock_destroy,pthread_rwlock_destroy) 55 56 int 57 pthread_rwlock_init(pthread_rwlock_t *rwlock, 58 const pthread_rwlockattr_t *attr) 59 { 60 #ifdef ERRORCHECK 61 if ((rwlock == NULL) || 62 (attr && (attr->ptra_magic != _PT_RWLOCKATTR_MAGIC))) 63 return EINVAL; 64 #endif 65 rwlock->ptr_magic = _PT_RWLOCK_MAGIC; 66 pthread_lockinit(&rwlock->ptr_interlock); 67 PTQ_INIT(&rwlock->ptr_rblocked); 68 PTQ_INIT(&rwlock->ptr_wblocked); 69 rwlock->ptr_nreaders = 0; 70 rwlock->ptr_writer = NULL; 71 72 return 0; 73 } 74 75 76 int 77 pthread_rwlock_destroy(pthread_rwlock_t *rwlock) 78 { 79 #ifdef ERRORCHECK 80 if ((rwlock == NULL) || 81 (rwlock->ptr_magic != _PT_RWLOCK_MAGIC) || 82 (!PTQ_EMPTY(&rwlock->ptr_rblocked)) || 83 (!PTQ_EMPTY(&rwlock->ptr_wblocked)) || 84 (rwlock->ptr_nreaders != 0) || 85 (rwlock->ptr_writer != NULL)) 86 return EINVAL; 87 #endif 88 rwlock->ptr_magic = _PT_RWLOCK_DEAD; 89 90 return 0; 91 } 92 93 94 int 95 pthread_rwlock_rdlock(pthread_rwlock_t *rwlock) 96 { 97 pthread_t self; 98 #ifdef ERRORCHECK 99 if ((rwlock == NULL) || (rwlock->ptr_magic != _PT_RWLOCK_MAGIC)) 100 return EINVAL; 101 #endif 102 self = pthread__self(); 103 104 pthread_spinlock(self, &rwlock->ptr_interlock); 105 #ifdef ERRORCHECK 106 if (rwlock->ptr_writer == self) { 107 pthread_spinunlock(self, &rwlock->ptr_interlock); 108 return EDEADLK; 109 } 110 #endif 111 /* 112 * Don't get a readlock if there is a writer or if there are waiting 113 * writers; i.e. prefer writers to readers. This strategy is dictated 114 * by SUSv3. 115 */ 116 while ((rwlock->ptr_writer != NULL) || 117 (!PTQ_EMPTY(&rwlock->ptr_wblocked))) { 118 PTQ_INSERT_TAIL(&rwlock->ptr_rblocked, self, pt_sleep); 119 /* Locking a rwlock is not a cancellation point; don't check */ 120 pthread_spinlock(self, &self->pt_statelock); 121 self->pt_state = PT_STATE_BLOCKED_QUEUE; 122 self->pt_sleepobj = rwlock; 123 self->pt_sleepq = &rwlock->ptr_rblocked; 124 self->pt_sleeplock = &rwlock->ptr_interlock; 125 pthread_spinunlock(self, &self->pt_statelock); 126 pthread__block(self, &rwlock->ptr_interlock); 127 /* interlock is not held when we return */ 128 pthread_spinlock(self, &rwlock->ptr_interlock); 129 } 130 131 rwlock->ptr_nreaders++; 132 pthread_spinunlock(self, &rwlock->ptr_interlock); 133 134 return 0; 135 } 136 137 138 int 139 pthread_rwlock_tryrdlock(pthread_rwlock_t *rwlock) 140 { 141 pthread_t self; 142 #ifdef ERRORCHECK 143 if ((rwlock == NULL) || (rwlock->ptr_magic != _PT_RWLOCK_MAGIC)) 144 return EINVAL; 145 #endif 146 self = pthread__self(); 147 148 pthread_spinlock(self, &rwlock->ptr_interlock); 149 #ifdef ERRORCHECK 150 if (rwlock->ptr_writer == self) { 151 pthread_spinunlock(self, &rwlock->ptr_interlock); 152 return EDEADLK; 153 } 154 #endif 155 /* 156 * Don't get a readlock if there is a writer or if there are waiting 157 * writers; i.e. prefer writers to readers. This strategy is dictated 158 * by SUSv3. 159 */ 160 if ((rwlock->ptr_writer != NULL) || 161 (!PTQ_EMPTY(&rwlock->ptr_wblocked))) { 162 pthread_spinunlock(self, &rwlock->ptr_interlock); 163 return EBUSY; 164 } 165 166 rwlock->ptr_nreaders++; 167 pthread_spinunlock(self, &rwlock->ptr_interlock); 168 169 return 0; 170 } 171 172 173 int 174 pthread_rwlock_wrlock(pthread_rwlock_t *rwlock) 175 { 176 pthread_t self; 177 #ifdef ERRORCHECK 178 if ((rwlock == NULL) || (rwlock->ptr_magic != _PT_RWLOCK_MAGIC)) 179 return EINVAL; 180 #endif 181 self = pthread__self(); 182 183 pthread_spinlock(self, &rwlock->ptr_interlock); 184 /* 185 * Prefer writers to readers here; permit writers even if there are 186 * waiting readers. 187 */ 188 while ((rwlock->ptr_nreaders > 0) || (rwlock->ptr_writer != NULL)) { 189 PTQ_INSERT_TAIL(&rwlock->ptr_wblocked, self, pt_sleep); 190 /* Locking a rwlock is not a cancellation point; don't check */ 191 pthread_spinlock(self, &self->pt_statelock); 192 self->pt_state = PT_STATE_BLOCKED_QUEUE; 193 self->pt_sleepobj = rwlock; 194 self->pt_sleepq = &rwlock->ptr_wblocked; 195 self->pt_sleeplock = &rwlock->ptr_interlock; 196 pthread_spinunlock(self, &self->pt_statelock); 197 pthread__block(self, &rwlock->ptr_interlock); 198 /* interlock is not held when we return */ 199 pthread_spinlock(self, &rwlock->ptr_interlock); 200 } 201 202 rwlock->ptr_writer = self; 203 pthread_spinunlock(self, &rwlock->ptr_interlock); 204 205 return 0; 206 } 207 208 209 int 210 pthread_rwlock_trywrlock(pthread_rwlock_t *rwlock) 211 { 212 pthread_t self; 213 #ifdef ERRORCHECK 214 if ((rwlock == NULL) || (rwlock->ptr_magic != _PT_RWLOCK_MAGIC)) 215 return EINVAL; 216 #endif 217 self = pthread__self(); 218 219 pthread_spinlock(self, &rwlock->ptr_interlock); 220 /* 221 * Prefer writers to readers here; permit writers even if there are 222 * waiting readers. 223 */ 224 if ((rwlock->ptr_nreaders > 0) || (rwlock->ptr_writer != NULL)) { 225 pthread_spinunlock(self, &rwlock->ptr_interlock); 226 return EBUSY; 227 } 228 229 rwlock->ptr_writer = self; 230 pthread_spinunlock(self, &rwlock->ptr_interlock); 231 232 return 0; 233 } 234 235 236 struct pthread_rwlock__waitarg { 237 pthread_t ptw_thread; 238 pthread_rwlock_t *ptw_rwlock; 239 struct pthread_queue_t *ptw_queue; 240 }; 241 242 int 243 pthread_rwlock_timedrdlock(pthread_rwlock_t *rwlock, 244 const struct timespec *abs_timeout) 245 { 246 pthread_t self; 247 struct pthread_rwlock__waitarg wait; 248 struct pt_alarm_t alarm; 249 int retval; 250 #ifdef ERRORCHECK 251 if ((rwlock == NULL) || (rwlock->ptr_magic != _PT_RWLOCK_MAGIC)) 252 return EINVAL; 253 #endif 254 self = pthread__self(); 255 256 pthread_spinlock(self, &rwlock->ptr_interlock); 257 #ifdef ERRORCHECK 258 if (rwlock->ptr_writer == self) { 259 pthread_spinlock(self, &rwlock->ptr_interlock); 260 return EDEADLK; 261 } 262 #endif 263 /* 264 * Don't get a readlock if there is a writer or if there are waiting 265 * writers; i.e. prefer writers to readers. This strategy is dictated 266 * by SUSv3. 267 */ 268 retval = 0; 269 while ((retval == 0) && ((rwlock->ptr_writer != NULL) || 270 (!PTQ_EMPTY(&rwlock->ptr_wblocked)))) { 271 wait.ptw_thread = self; 272 wait.ptw_rwlock = rwlock; 273 wait.ptw_queue = &rwlock->ptr_rblocked; 274 pthread__alarm_add(self, &alarm, abs_timeout, 275 pthread_rwlock__callback, &wait); 276 PTQ_INSERT_TAIL(&rwlock->ptr_rblocked, self, pt_sleep); 277 /* Locking a rwlock is not a cancellation point; don't check */ 278 pthread_spinlock(self, &self->pt_statelock); 279 self->pt_state = PT_STATE_BLOCKED_QUEUE; 280 self->pt_sleepobj = rwlock; 281 self->pt_sleepq = &rwlock->ptr_rblocked; 282 self->pt_sleeplock = &rwlock->ptr_interlock; 283 pthread_spinunlock(self, &self->pt_statelock); 284 pthread__block(self, &rwlock->ptr_interlock); 285 /* interlock is not held when we return */ 286 pthread__alarm_del(self, &alarm); 287 if (pthread__alarm_fired(&alarm)) 288 retval = ETIMEDOUT; 289 pthread_spinlock(self, &rwlock->ptr_interlock); 290 } 291 292 if (retval == 0) 293 rwlock->ptr_nreaders++; 294 pthread_spinunlock(self, &rwlock->ptr_interlock); 295 296 return retval; 297 } 298 299 300 int 301 pthread_rwlock_timedwrlock(pthread_rwlock_t *rwlock, 302 const struct timespec *abs_timeout) 303 { 304 struct pthread_rwlock__waitarg wait; 305 struct pt_alarm_t alarm; 306 int retval; 307 pthread_t self; 308 #ifdef ERRORCHECK 309 if ((rwlock == NULL) || (rwlock->ptr_magic != _PT_RWLOCK_MAGIC)) 310 return EINVAL; 311 #endif 312 self = pthread__self(); 313 314 pthread_spinlock(self, &rwlock->ptr_interlock); 315 /* 316 * Prefer writers to readers here; permit writers even if there are 317 * waiting readers. 318 */ 319 retval = 0; 320 while (retval == 0 && 321 ((rwlock->ptr_nreaders > 0) || (rwlock->ptr_writer != NULL))) { 322 wait.ptw_thread = self; 323 wait.ptw_rwlock = rwlock; 324 wait.ptw_queue = &rwlock->ptr_wblocked; 325 pthread__alarm_add(self, &alarm, abs_timeout, 326 pthread_rwlock__callback, &wait); 327 PTQ_INSERT_TAIL(&rwlock->ptr_wblocked, self, pt_sleep); 328 /* Locking a rwlock is not a cancellation point; don't check */ 329 pthread_spinlock(self, &self->pt_statelock); 330 self->pt_state = PT_STATE_BLOCKED_QUEUE; 331 self->pt_sleepobj = rwlock; 332 self->pt_sleepq = &rwlock->ptr_wblocked; 333 self->pt_sleeplock = &rwlock->ptr_interlock; 334 pthread_spinunlock(self, &self->pt_statelock); 335 pthread__block(self, &rwlock->ptr_interlock); 336 /* interlock is not held when we return */ 337 pthread__alarm_del(self, &alarm); 338 if (pthread__alarm_fired(&alarm)) 339 retval = ETIMEDOUT; 340 pthread_spinlock(self, &rwlock->ptr_interlock); 341 } 342 343 if (retval == 0) 344 rwlock->ptr_writer = self; 345 pthread_spinunlock(self, &rwlock->ptr_interlock); 346 347 return 0; 348 } 349 350 351 static void 352 pthread_rwlock__callback(void *arg) 353 { 354 struct pthread_rwlock__waitarg *a; 355 pthread_t self; 356 357 a = arg; 358 self = pthread__self(); 359 360 pthread_spinlock(self, &a->ptw_rwlock->ptr_interlock); 361 /* 362 * Don't dequeue and schedule the thread if it's already been 363 * queued up by a signal or broadcast (but hasn't yet run as far 364 * as pthread__alarm_del(), or we wouldn't be here, and hence can't 365 * have become blocked on some *other* queue). 366 */ 367 if (a->ptw_thread->pt_state == PT_STATE_BLOCKED_QUEUE) { 368 PTQ_REMOVE(a->ptw_queue, a->ptw_thread, pt_sleep); 369 pthread__sched(self, a->ptw_thread); 370 } 371 pthread_spinunlock(self, &a->ptw_rwlock->ptr_interlock); 372 373 } 374 375 376 int 377 pthread_rwlock_unlock(pthread_rwlock_t *rwlock) 378 { 379 pthread_t self, reader, writer; 380 struct pthread_queue_t blockedq; 381 #ifdef ERRORCHECK 382 if ((rwlock == NULL) || (rwlock->ptr_magic != _PT_RWLOCK_MAGIC)) 383 return EINVAL; 384 #endif 385 writer = NULL; 386 PTQ_INIT(&blockedq); 387 self = pthread__self(); 388 389 pthread_spinlock(self, &rwlock->ptr_interlock); 390 if (rwlock->ptr_writer != NULL) { 391 /* Releasing a write lock. */ 392 #ifdef ERRORCHECK 393 if (rwlock->ptr_writer != self) { 394 pthread_spinunlock(self, &rwlock->ptr_interlock); 395 return EPERM; 396 } 397 #endif 398 rwlock->ptr_writer = NULL; 399 writer = PTQ_FIRST(&rwlock->ptr_wblocked); 400 if (writer != NULL) { 401 PTQ_REMOVE(&rwlock->ptr_wblocked, writer, pt_sleep); 402 } else { 403 blockedq = rwlock->ptr_rblocked; 404 PTQ_INIT(&rwlock->ptr_rblocked); 405 } 406 } else { 407 /* Releasing a read lock. */ 408 rwlock->ptr_nreaders--; 409 if (rwlock->ptr_nreaders == 0) { 410 writer = PTQ_FIRST(&rwlock->ptr_wblocked); 411 if (writer != NULL) 412 PTQ_REMOVE(&rwlock->ptr_wblocked, writer, 413 pt_sleep); 414 } 415 } 416 417 pthread_spinunlock(self, &rwlock->ptr_interlock); 418 419 if (writer != NULL) 420 pthread__sched(self, writer); 421 else 422 PTQ_FOREACH(reader, &blockedq, pt_sleep) 423 pthread__sched(self, reader); 424 425 return 0; 426 } 427 428 429 int 430 pthread_rwlockattr_init(pthread_rwlockattr_t *attr) 431 { 432 #ifdef ERRORCHECK 433 if (attr == NULL) 434 return EINVAL; 435 #endif 436 attr->ptra_magic = _PT_RWLOCKATTR_MAGIC; 437 438 return 0; 439 } 440 441 442 int 443 pthread_rwlockattr_destroy(pthread_rwlockattr_t *attr) 444 { 445 #ifdef ERRORCHECK 446 if ((attr == NULL) || 447 (attr->ptra_magic != _PT_RWLOCKATTR_MAGIC)) 448 return EINVAL; 449 #endif 450 attr->ptra_magic = _PT_RWLOCKATTR_DEAD; 451 452 return 0; 453 } 454
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