pthread_rwlock.c revision 1.7.2.1
1 /* $NetBSD: pthread_rwlock.c,v 1.7.2.1 2004/08/12 04:22:36 jmc 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 <sys/cdefs.h> 40 __RCSID("$NetBSD: pthread_rwlock.c,v 1.7.2.1 2004/08/12 04:22:36 jmc Exp $"); 41 42 #include <errno.h> 43 44 #include "pthread.h" 45 #include "pthread_int.h" 46 47 static void pthread_rwlock__callback(void *); 48 49 __strong_alias(__libc_rwlock_init,pthread_rwlock_init) 50 __strong_alias(__libc_rwlock_rdlock,pthread_rwlock_rdlock) 51 __strong_alias(__libc_rwlock_wrlock,pthread_rwlock_wrlock) 52 __strong_alias(__libc_rwlock_tryrdlock,pthread_rwlock_tryrdlock) 53 __strong_alias(__libc_rwlock_trywrlock,pthread_rwlock_trywrlock) 54 __strong_alias(__libc_rwlock_unlock,pthread_rwlock_unlock) 55 __strong_alias(__libc_rwlock_destroy,pthread_rwlock_destroy) 56 57 int 58 pthread_rwlock_init(pthread_rwlock_t *rwlock, 59 const pthread_rwlockattr_t *attr) 60 { 61 #ifdef ERRORCHECK 62 if ((rwlock == NULL) || 63 (attr && (attr->ptra_magic != _PT_RWLOCKATTR_MAGIC))) 64 return EINVAL; 65 #endif 66 rwlock->ptr_magic = _PT_RWLOCK_MAGIC; 67 pthread_lockinit(&rwlock->ptr_interlock); 68 PTQ_INIT(&rwlock->ptr_rblocked); 69 PTQ_INIT(&rwlock->ptr_wblocked); 70 rwlock->ptr_nreaders = 0; 71 rwlock->ptr_writer = NULL; 72 73 return 0; 74 } 75 76 77 int 78 pthread_rwlock_destroy(pthread_rwlock_t *rwlock) 79 { 80 #ifdef ERRORCHECK 81 if ((rwlock == NULL) || 82 (rwlock->ptr_magic != _PT_RWLOCK_MAGIC) || 83 (!PTQ_EMPTY(&rwlock->ptr_rblocked)) || 84 (!PTQ_EMPTY(&rwlock->ptr_wblocked)) || 85 (rwlock->ptr_nreaders != 0) || 86 (rwlock->ptr_writer != NULL)) 87 return EINVAL; 88 #endif 89 rwlock->ptr_magic = _PT_RWLOCK_DEAD; 90 91 return 0; 92 } 93 94 95 int 96 pthread_rwlock_rdlock(pthread_rwlock_t *rwlock) 97 { 98 pthread_t self; 99 #ifdef ERRORCHECK 100 if ((rwlock == NULL) || (rwlock->ptr_magic != _PT_RWLOCK_MAGIC)) 101 return EINVAL; 102 #endif 103 self = pthread__self(); 104 105 pthread_spinlock(self, &rwlock->ptr_interlock); 106 #ifdef ERRORCHECK 107 if (rwlock->ptr_writer == self) { 108 pthread_spinunlock(self, &rwlock->ptr_interlock); 109 return EDEADLK; 110 } 111 #endif 112 /* 113 * Don't get a readlock if there is a writer or if there are waiting 114 * writers; i.e. prefer writers to readers. This strategy is dictated 115 * by SUSv3. 116 */ 117 while ((rwlock->ptr_writer != NULL) || 118 (!PTQ_EMPTY(&rwlock->ptr_wblocked))) { 119 PTQ_INSERT_TAIL(&rwlock->ptr_rblocked, self, pt_sleep); 120 /* Locking a rwlock is not a cancellation point; don't check */ 121 pthread_spinlock(self, &self->pt_statelock); 122 self->pt_state = PT_STATE_BLOCKED_QUEUE; 123 self->pt_sleepobj = rwlock; 124 self->pt_sleepq = &rwlock->ptr_rblocked; 125 self->pt_sleeplock = &rwlock->ptr_interlock; 126 pthread_spinunlock(self, &self->pt_statelock); 127 pthread__block(self, &rwlock->ptr_interlock); 128 /* interlock is not held when we return */ 129 pthread_spinlock(self, &rwlock->ptr_interlock); 130 } 131 132 rwlock->ptr_nreaders++; 133 pthread_spinunlock(self, &rwlock->ptr_interlock); 134 135 return 0; 136 } 137 138 139 int 140 pthread_rwlock_tryrdlock(pthread_rwlock_t *rwlock) 141 { 142 pthread_t self; 143 #ifdef ERRORCHECK 144 if ((rwlock == NULL) || (rwlock->ptr_magic != _PT_RWLOCK_MAGIC)) 145 return EINVAL; 146 #endif 147 self = pthread__self(); 148 149 pthread_spinlock(self, &rwlock->ptr_interlock); 150 /* 151 * Don't get a readlock if there is a writer or if there are waiting 152 * writers; i.e. prefer writers to readers. This strategy is dictated 153 * by SUSv3. 154 */ 155 if ((rwlock->ptr_writer != NULL) || 156 (!PTQ_EMPTY(&rwlock->ptr_wblocked))) { 157 pthread_spinunlock(self, &rwlock->ptr_interlock); 158 return EBUSY; 159 } 160 161 rwlock->ptr_nreaders++; 162 pthread_spinunlock(self, &rwlock->ptr_interlock); 163 164 return 0; 165 } 166 167 168 int 169 pthread_rwlock_wrlock(pthread_rwlock_t *rwlock) 170 { 171 pthread_t self; 172 #ifdef ERRORCHECK 173 if ((rwlock == NULL) || (rwlock->ptr_magic != _PT_RWLOCK_MAGIC)) 174 return EINVAL; 175 #endif 176 self = pthread__self(); 177 178 pthread_spinlock(self, &rwlock->ptr_interlock); 179 #ifdef ERRORCHECK 180 if (rwlock->ptr_writer == self) { 181 pthread_spinunlock(self, &rwlock->ptr_interlock); 182 return EDEADLK; 183 } 184 #endif 185 /* 186 * Prefer writers to readers here; permit writers even if there are 187 * waiting readers. 188 */ 189 while ((rwlock->ptr_nreaders > 0) || (rwlock->ptr_writer != NULL)) { 190 PTQ_INSERT_TAIL(&rwlock->ptr_wblocked, self, pt_sleep); 191 /* Locking a rwlock is not a cancellation point; don't check */ 192 pthread_spinlock(self, &self->pt_statelock); 193 self->pt_state = PT_STATE_BLOCKED_QUEUE; 194 self->pt_sleepobj = rwlock; 195 self->pt_sleepq = &rwlock->ptr_wblocked; 196 self->pt_sleeplock = &rwlock->ptr_interlock; 197 pthread_spinunlock(self, &self->pt_statelock); 198 pthread__block(self, &rwlock->ptr_interlock); 199 /* interlock is not held when we return */ 200 pthread_spinlock(self, &rwlock->ptr_interlock); 201 } 202 203 rwlock->ptr_writer = self; 204 pthread_spinunlock(self, &rwlock->ptr_interlock); 205 206 return 0; 207 } 208 209 210 int 211 pthread_rwlock_trywrlock(pthread_rwlock_t *rwlock) 212 { 213 pthread_t self; 214 #ifdef ERRORCHECK 215 if ((rwlock == NULL) || (rwlock->ptr_magic != _PT_RWLOCK_MAGIC)) 216 return EINVAL; 217 #endif 218 self = pthread__self(); 219 220 pthread_spinlock(self, &rwlock->ptr_interlock); 221 /* 222 * Prefer writers to readers here; permit writers even if there are 223 * waiting readers. 224 */ 225 if ((rwlock->ptr_nreaders > 0) || (rwlock->ptr_writer != NULL)) { 226 pthread_spinunlock(self, &rwlock->ptr_interlock); 227 return EBUSY; 228 } 229 230 rwlock->ptr_writer = self; 231 pthread_spinunlock(self, &rwlock->ptr_interlock); 232 233 return 0; 234 } 235 236 237 struct pthread_rwlock__waitarg { 238 pthread_t ptw_thread; 239 pthread_rwlock_t *ptw_rwlock; 240 struct pthread_queue_t *ptw_queue; 241 }; 242 243 int 244 pthread_rwlock_timedrdlock(pthread_rwlock_t *rwlock, 245 const struct timespec *abs_timeout) 246 { 247 pthread_t self; 248 struct pthread_rwlock__waitarg wait; 249 struct pt_alarm_t alarm; 250 int retval; 251 #ifdef ERRORCHECK 252 if ((rwlock == NULL) || (rwlock->ptr_magic != _PT_RWLOCK_MAGIC)) 253 return EINVAL; 254 if ((abs_timeout == NULL) || (abs_timeout->tv_nsec >= 1000000000)) 255 return EINVAL; 256 #endif 257 self = pthread__self(); 258 259 pthread_spinlock(self, &rwlock->ptr_interlock); 260 #ifdef ERRORCHECK 261 if (rwlock->ptr_writer == self) { 262 pthread_spinlock(self, &rwlock->ptr_interlock); 263 return EDEADLK; 264 } 265 #endif 266 /* 267 * Don't get a readlock if there is a writer or if there are waiting 268 * writers; i.e. prefer writers to readers. This strategy is dictated 269 * by SUSv3. 270 */ 271 retval = 0; 272 while ((retval == 0) && ((rwlock->ptr_writer != NULL) || 273 (!PTQ_EMPTY(&rwlock->ptr_wblocked)))) { 274 wait.ptw_thread = self; 275 wait.ptw_rwlock = rwlock; 276 wait.ptw_queue = &rwlock->ptr_rblocked; 277 pthread__alarm_add(self, &alarm, abs_timeout, 278 pthread_rwlock__callback, &wait); 279 PTQ_INSERT_TAIL(&rwlock->ptr_rblocked, self, pt_sleep); 280 /* Locking a rwlock is not a cancellation point; don't check */ 281 pthread_spinlock(self, &self->pt_statelock); 282 self->pt_state = PT_STATE_BLOCKED_QUEUE; 283 self->pt_sleepobj = rwlock; 284 self->pt_sleepq = &rwlock->ptr_rblocked; 285 self->pt_sleeplock = &rwlock->ptr_interlock; 286 pthread_spinunlock(self, &self->pt_statelock); 287 pthread__block(self, &rwlock->ptr_interlock); 288 /* interlock is not held when we return */ 289 pthread__alarm_del(self, &alarm); 290 if (pthread__alarm_fired(&alarm)) 291 retval = ETIMEDOUT; 292 pthread_spinlock(self, &rwlock->ptr_interlock); 293 } 294 295 if (retval == 0) 296 rwlock->ptr_nreaders++; 297 pthread_spinunlock(self, &rwlock->ptr_interlock); 298 299 return retval; 300 } 301 302 303 int 304 pthread_rwlock_timedwrlock(pthread_rwlock_t *rwlock, 305 const struct timespec *abs_timeout) 306 { 307 struct pthread_rwlock__waitarg wait; 308 struct pt_alarm_t alarm; 309 int retval; 310 pthread_t self; 311 #ifdef ERRORCHECK 312 if ((rwlock == NULL) || (rwlock->ptr_magic != _PT_RWLOCK_MAGIC)) 313 return EINVAL; 314 #endif 315 self = pthread__self(); 316 317 pthread_spinlock(self, &rwlock->ptr_interlock); 318 #ifdef ERRORCHECK 319 if (rwlock->ptr_writer == self) { 320 pthread_spinlock(self, &rwlock->ptr_interlock); 321 return EDEADLK; 322 } 323 #endif 324 /* 325 * Prefer writers to readers here; permit writers even if there are 326 * waiting readers. 327 */ 328 retval = 0; 329 while (retval == 0 && 330 ((rwlock->ptr_nreaders > 0) || (rwlock->ptr_writer != NULL))) { 331 wait.ptw_thread = self; 332 wait.ptw_rwlock = rwlock; 333 wait.ptw_queue = &rwlock->ptr_wblocked; 334 pthread__alarm_add(self, &alarm, abs_timeout, 335 pthread_rwlock__callback, &wait); 336 PTQ_INSERT_TAIL(&rwlock->ptr_wblocked, self, pt_sleep); 337 /* Locking a rwlock is not a cancellation point; don't check */ 338 pthread_spinlock(self, &self->pt_statelock); 339 self->pt_state = PT_STATE_BLOCKED_QUEUE; 340 self->pt_sleepobj = rwlock; 341 self->pt_sleepq = &rwlock->ptr_wblocked; 342 self->pt_sleeplock = &rwlock->ptr_interlock; 343 pthread_spinunlock(self, &self->pt_statelock); 344 pthread__block(self, &rwlock->ptr_interlock); 345 /* interlock is not held when we return */ 346 pthread__alarm_del(self, &alarm); 347 if (pthread__alarm_fired(&alarm)) 348 retval = ETIMEDOUT; 349 pthread_spinlock(self, &rwlock->ptr_interlock); 350 } 351 352 if (retval == 0) 353 rwlock->ptr_writer = self; 354 pthread_spinunlock(self, &rwlock->ptr_interlock); 355 356 return retval; 357 } 358 359 360 static void 361 pthread_rwlock__callback(void *arg) 362 { 363 struct pthread_rwlock__waitarg *a; 364 pthread_t self; 365 366 a = arg; 367 self = pthread__self(); 368 369 pthread_spinlock(self, &a->ptw_rwlock->ptr_interlock); 370 /* 371 * Don't dequeue and schedule the thread if it's already been 372 * queued up by a signal or broadcast (but hasn't yet run as far 373 * as pthread__alarm_del(), or we wouldn't be here, and hence can't 374 * have become blocked on some *other* queue). 375 */ 376 if (a->ptw_thread->pt_state == PT_STATE_BLOCKED_QUEUE) { 377 PTQ_REMOVE(a->ptw_queue, a->ptw_thread, pt_sleep); 378 pthread__sched(self, a->ptw_thread); 379 } 380 pthread_spinunlock(self, &a->ptw_rwlock->ptr_interlock); 381 382 } 383 384 385 int 386 pthread_rwlock_unlock(pthread_rwlock_t *rwlock) 387 { 388 pthread_t self, writer; 389 struct pthread_queue_t blockedq; 390 #ifdef ERRORCHECK 391 if ((rwlock == NULL) || (rwlock->ptr_magic != _PT_RWLOCK_MAGIC)) 392 return EINVAL; 393 #endif 394 writer = NULL; 395 PTQ_INIT(&blockedq); 396 self = pthread__self(); 397 398 pthread_spinlock(self, &rwlock->ptr_interlock); 399 if (rwlock->ptr_writer != NULL) { 400 /* Releasing a write lock. */ 401 #ifdef ERRORCHECK 402 if (rwlock->ptr_writer != self) { 403 pthread_spinunlock(self, &rwlock->ptr_interlock); 404 return EPERM; 405 } 406 #endif 407 rwlock->ptr_writer = NULL; 408 writer = PTQ_FIRST(&rwlock->ptr_wblocked); 409 if (writer != NULL) { 410 PTQ_REMOVE(&rwlock->ptr_wblocked, writer, pt_sleep); 411 } else { 412 blockedq = rwlock->ptr_rblocked; 413 PTQ_INIT(&rwlock->ptr_rblocked); 414 } 415 } else 416 #ifdef ERRORCHECK 417 if (rwlock->ptr_nreaders > 0) 418 #endif 419 { 420 /* Releasing a read lock. */ 421 rwlock->ptr_nreaders--; 422 if (rwlock->ptr_nreaders == 0) { 423 writer = PTQ_FIRST(&rwlock->ptr_wblocked); 424 if (writer != NULL) 425 PTQ_REMOVE(&rwlock->ptr_wblocked, writer, 426 pt_sleep); 427 } 428 #ifdef ERRORCHECK 429 } else { 430 pthread_spinunlock(self, &rwlock->ptr_interlock); 431 return EPERM; 432 #endif 433 } 434 435 if (writer != NULL) 436 pthread__sched(self, writer); 437 else 438 pthread__sched_sleepers(self, &blockedq); 439 440 pthread_spinunlock(self, &rwlock->ptr_interlock); 441 442 return 0; 443 } 444 445 446 int 447 pthread_rwlockattr_init(pthread_rwlockattr_t *attr) 448 { 449 #ifdef ERRORCHECK 450 if (attr == NULL) 451 return EINVAL; 452 #endif 453 attr->ptra_magic = _PT_RWLOCKATTR_MAGIC; 454 455 return 0; 456 } 457 458 459 int 460 pthread_rwlockattr_destroy(pthread_rwlockattr_t *attr) 461 { 462 #ifdef ERRORCHECK 463 if ((attr == NULL) || 464 (attr->ptra_magic != _PT_RWLOCKATTR_MAGIC)) 465 return EINVAL; 466 #endif 467 attr->ptra_magic = _PT_RWLOCKATTR_DEAD; 468 469 return 0; 470 } 471
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