pthread_rwlock.c revision 1.19
1 /* $NetBSD: pthread_rwlock.c,v 1.19 2007/08/04 13:37:50 ad Exp $ */ 2 3 /*- 4 * Copyright (c) 2002, 2006, 2007 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 and Andrew Doran. 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 1.19 2007/08/04 13:37:50 ad Exp $"); 41 42 #include <errno.h> 43 44 #include "pthread.h" 45 #include "pthread_int.h" 46 47 __strong_alias(__libc_rwlock_init,pthread_rwlock_init) 48 __strong_alias(__libc_rwlock_rdlock,pthread_rwlock_rdlock) 49 __strong_alias(__libc_rwlock_wrlock,pthread_rwlock_wrlock) 50 __strong_alias(__libc_rwlock_tryrdlock,pthread_rwlock_tryrdlock) 51 __strong_alias(__libc_rwlock_trywrlock,pthread_rwlock_trywrlock) 52 __strong_alias(__libc_rwlock_unlock,pthread_rwlock_unlock) 53 __strong_alias(__libc_rwlock_destroy,pthread_rwlock_destroy) 54 55 int 56 pthread_rwlock_init(pthread_rwlock_t *rwlock, 57 const pthread_rwlockattr_t *attr) 58 { 59 #ifdef ERRORCHECK 60 if ((rwlock == NULL) || 61 (attr && (attr->ptra_magic != _PT_RWLOCKATTR_MAGIC))) 62 return EINVAL; 63 #endif 64 rwlock->ptr_magic = _PT_RWLOCK_MAGIC; 65 pthread_lockinit(&rwlock->ptr_interlock); 66 PTQ_INIT(&rwlock->ptr_rblocked); 67 PTQ_INIT(&rwlock->ptr_wblocked); 68 rwlock->ptr_nreaders = 0; 69 rwlock->ptr_writer = NULL; 70 71 return 0; 72 } 73 74 75 int 76 pthread_rwlock_destroy(pthread_rwlock_t *rwlock) 77 { 78 #ifdef ERRORCHECK 79 if ((rwlock == NULL) || 80 (rwlock->ptr_magic != _PT_RWLOCK_MAGIC) || 81 (!PTQ_EMPTY(&rwlock->ptr_rblocked)) || 82 (!PTQ_EMPTY(&rwlock->ptr_wblocked)) || 83 (rwlock->ptr_nreaders != 0) || 84 (rwlock->ptr_writer != NULL)) 85 return EINVAL; 86 #endif 87 rwlock->ptr_magic = _PT_RWLOCK_DEAD; 88 89 return 0; 90 } 91 92 93 int 94 pthread_rwlock_rdlock(pthread_rwlock_t *rwlock) 95 { 96 pthread_t self; 97 #ifdef ERRORCHECK 98 if ((rwlock == NULL) || (rwlock->ptr_magic != _PT_RWLOCK_MAGIC)) 99 return EINVAL; 100 #endif 101 self = pthread__self(); 102 103 pthread_spinlock(self, &rwlock->ptr_interlock); 104 #ifdef ERRORCHECK 105 if (rwlock->ptr_writer == self) { 106 pthread_spinunlock(self, &rwlock->ptr_interlock); 107 return EDEADLK; 108 } 109 #endif 110 /* 111 * Don't get a readlock if there is a writer or if there are waiting 112 * writers; i.e. prefer writers to readers. This strategy is dictated 113 * by SUSv3. 114 */ 115 while ((rwlock->ptr_writer != NULL) || 116 (!PTQ_EMPTY(&rwlock->ptr_wblocked))) { 117 PTQ_INSERT_TAIL(&rwlock->ptr_rblocked, self, pt_sleep); 118 self->pt_sleeponq = 1; 119 self->pt_sleepobj = &rwlock->ptr_rblocked; 120 pthread_spinunlock(self, &rwlock->ptr_interlock); 121 (void)pthread__park(self, &rwlock->ptr_interlock, 122 &rwlock->ptr_rblocked, NULL, 0, &rwlock->ptr_rblocked); 123 pthread_spinlock(self, &rwlock->ptr_interlock); 124 } 125 126 rwlock->ptr_nreaders++; 127 pthread_spinunlock(self, &rwlock->ptr_interlock); 128 129 return 0; 130 } 131 132 133 int 134 pthread_rwlock_tryrdlock(pthread_rwlock_t *rwlock) 135 { 136 pthread_t self; 137 #ifdef ERRORCHECK 138 if ((rwlock == NULL) || (rwlock->ptr_magic != _PT_RWLOCK_MAGIC)) 139 return EINVAL; 140 #endif 141 self = pthread__self(); 142 143 pthread_spinlock(self, &rwlock->ptr_interlock); 144 /* 145 * Don't get a readlock if there is a writer or if there are waiting 146 * writers; i.e. prefer writers to readers. This strategy is dictated 147 * by SUSv3. 148 */ 149 if ((rwlock->ptr_writer != NULL) || 150 (!PTQ_EMPTY(&rwlock->ptr_wblocked))) { 151 pthread_spinunlock(self, &rwlock->ptr_interlock); 152 return EBUSY; 153 } 154 155 rwlock->ptr_nreaders++; 156 pthread_spinunlock(self, &rwlock->ptr_interlock); 157 158 return 0; 159 } 160 161 162 int 163 pthread_rwlock_wrlock(pthread_rwlock_t *rwlock) 164 { 165 pthread_t self; 166 extern int pthread__started; 167 168 #ifdef ERRORCHECK 169 if ((rwlock == NULL) || (rwlock->ptr_magic != _PT_RWLOCK_MAGIC)) 170 return EINVAL; 171 #endif 172 self = pthread__self(); 173 174 pthread_spinlock(self, &rwlock->ptr_interlock); 175 #ifdef ERRORCHECK 176 if (rwlock->ptr_writer == self) { 177 pthread_spinunlock(self, &rwlock->ptr_interlock); 178 return EDEADLK; 179 } 180 #endif 181 /* 182 * Prefer writers to readers here; permit writers even if there are 183 * waiting readers. 184 */ 185 while ((rwlock->ptr_nreaders > 0) || (rwlock->ptr_writer != NULL)) { 186 #ifdef ERRORCHECK 187 if (pthread__started == 0) { 188 pthread_spinunlock(self, &rwlock->ptr_interlock); 189 return EDEADLK; 190 } 191 #endif 192 PTQ_INSERT_TAIL(&rwlock->ptr_wblocked, self, pt_sleep); 193 self->pt_sleeponq = 1; 194 self->pt_sleepobj = &rwlock->ptr_wblocked; 195 pthread_spinunlock(self, &rwlock->ptr_interlock); 196 (void)pthread__park(self, &rwlock->ptr_interlock, 197 &rwlock->ptr_wblocked, NULL, 0, &rwlock->ptr_wblocked); 198 pthread_spinlock(self, &rwlock->ptr_interlock); 199 } 200 201 rwlock->ptr_writer = self; 202 pthread_spinunlock(self, &rwlock->ptr_interlock); 203 204 return 0; 205 } 206 207 208 int 209 pthread_rwlock_trywrlock(pthread_rwlock_t *rwlock) 210 { 211 pthread_t self; 212 #ifdef ERRORCHECK 213 if ((rwlock == NULL) || (rwlock->ptr_magic != _PT_RWLOCK_MAGIC)) 214 return EINVAL; 215 #endif 216 self = pthread__self(); 217 218 pthread_spinlock(self, &rwlock->ptr_interlock); 219 /* 220 * Prefer writers to readers here; permit writers even if there are 221 * waiting readers. 222 */ 223 if ((rwlock->ptr_nreaders > 0) || (rwlock->ptr_writer != NULL)) { 224 pthread_spinunlock(self, &rwlock->ptr_interlock); 225 return EBUSY; 226 } 227 228 rwlock->ptr_writer = self; 229 pthread_spinunlock(self, &rwlock->ptr_interlock); 230 231 return 0; 232 } 233 234 235 int 236 pthread_rwlock_timedrdlock(pthread_rwlock_t *rwlock, 237 const struct timespec *abs_timeout) 238 { 239 pthread_t self; 240 int retval; 241 242 #ifdef ERRORCHECK 243 if ((rwlock == NULL) || (rwlock->ptr_magic != _PT_RWLOCK_MAGIC)) 244 return EINVAL; 245 if (abs_timeout == NULL) 246 return EINVAL; 247 #endif 248 if ((abs_timeout->tv_nsec >= 1000000000) || 249 (abs_timeout->tv_nsec < 0) || 250 (abs_timeout->tv_sec < 0)) 251 return EINVAL; 252 253 self = pthread__self(); 254 pthread_spinlock(self, &rwlock->ptr_interlock); 255 #ifdef ERRORCHECK 256 if (rwlock->ptr_writer == self) { 257 pthread_spinunlock(self, &rwlock->ptr_interlock); 258 return EDEADLK; 259 } 260 #endif 261 /* 262 * Don't get a readlock if there is a writer or if there are waiting 263 * writers; i.e. prefer writers to readers. This strategy is dictated 264 * by SUSv3. 265 */ 266 retval = 0; 267 while ((retval == 0) && ((rwlock->ptr_writer != NULL) || 268 (!PTQ_EMPTY(&rwlock->ptr_wblocked)))) { 269 PTQ_INSERT_TAIL(&rwlock->ptr_rblocked, self, pt_sleep); 270 self->pt_sleeponq = 1; 271 self->pt_sleepobj = &rwlock->ptr_rblocked; 272 pthread_spinunlock(self, &rwlock->ptr_interlock); 273 retval = pthread__park(self, &rwlock->ptr_interlock, 274 &rwlock->ptr_rblocked, abs_timeout, 0, 275 &rwlock->ptr_rblocked); 276 pthread_spinlock(self, &rwlock->ptr_interlock); 277 } 278 279 /* One last chance to get the lock, in case it was released between 280 the alarm firing and when this thread got rescheduled, or in case 281 a signal handler kept it busy */ 282 if ((rwlock->ptr_writer == NULL) && 283 (PTQ_EMPTY(&rwlock->ptr_wblocked))) { 284 rwlock->ptr_nreaders++; 285 retval = 0; 286 } 287 pthread_spinunlock(self, &rwlock->ptr_interlock); 288 289 return retval; 290 } 291 292 293 int 294 pthread_rwlock_timedwrlock(pthread_rwlock_t *rwlock, 295 const struct timespec *abs_timeout) 296 { 297 pthread_t self; 298 int retval; 299 extern int pthread__started; 300 301 #ifdef ERRORCHECK 302 if ((rwlock == NULL) || (rwlock->ptr_magic != _PT_RWLOCK_MAGIC)) 303 return EINVAL; 304 if (abs_timeout == NULL) 305 return EINVAL; 306 #endif 307 if ((abs_timeout->tv_nsec >= 1000000000) || 308 (abs_timeout->tv_nsec < 0) || 309 (abs_timeout->tv_sec < 0)) 310 return EINVAL; 311 312 self = pthread__self(); 313 pthread_spinlock(self, &rwlock->ptr_interlock); 314 #ifdef ERRORCHECK 315 if (rwlock->ptr_writer == self) { 316 pthread_spinunlock(self, &rwlock->ptr_interlock); 317 return EDEADLK; 318 } 319 #endif 320 /* 321 * Prefer writers to readers here; permit writers even if there are 322 * waiting readers. 323 */ 324 retval = 0; 325 while (retval == 0 && 326 ((rwlock->ptr_nreaders > 0) || (rwlock->ptr_writer != NULL))) { 327 #ifdef ERRORCHECK 328 if (pthread__started == 0) { 329 pthread_spinunlock(self, &rwlock->ptr_interlock); 330 return EDEADLK; 331 } 332 #endif 333 PTQ_INSERT_TAIL(&rwlock->ptr_wblocked, self, pt_sleep); 334 self->pt_sleeponq = 1; 335 self->pt_sleepobj = &rwlock->ptr_wblocked; 336 pthread_spinunlock(self, &rwlock->ptr_interlock); 337 retval = pthread__park(self, &rwlock->ptr_interlock, 338 &rwlock->ptr_wblocked, abs_timeout, 0, 339 &rwlock->ptr_wblocked); 340 pthread_spinlock(self, &rwlock->ptr_interlock); 341 } 342 343 if ((rwlock->ptr_nreaders == 0) && (rwlock->ptr_writer == NULL)) { 344 rwlock->ptr_writer = self; 345 retval = 0; 346 } 347 pthread_spinunlock(self, &rwlock->ptr_interlock); 348 349 return retval; 350 } 351 352 353 int 354 pthread_rwlock_unlock(pthread_rwlock_t *rwlock) 355 { 356 pthread_t self, writer; 357 #ifdef ERRORCHECK 358 if ((rwlock == NULL) || (rwlock->ptr_magic != _PT_RWLOCK_MAGIC)) 359 return EINVAL; 360 #endif 361 writer = NULL; 362 self = pthread__self(); 363 364 pthread_spinlock(self, &rwlock->ptr_interlock); 365 if (rwlock->ptr_writer != NULL) { 366 /* Releasing a write lock. */ 367 #ifdef ERRORCHECK 368 if (rwlock->ptr_writer != self) { 369 pthread_spinunlock(self, &rwlock->ptr_interlock); 370 return EPERM; 371 } 372 #endif 373 rwlock->ptr_writer = NULL; 374 writer = PTQ_FIRST(&rwlock->ptr_wblocked); 375 if (writer != NULL) { 376 PTQ_REMOVE(&rwlock->ptr_wblocked, writer, pt_sleep); 377 } 378 } else 379 #ifdef ERRORCHECK 380 if (rwlock->ptr_nreaders > 0) 381 #endif 382 { 383 /* Releasing a read lock. */ 384 rwlock->ptr_nreaders--; 385 if (rwlock->ptr_nreaders == 0) { 386 writer = PTQ_FIRST(&rwlock->ptr_wblocked); 387 if (writer != NULL) 388 PTQ_REMOVE(&rwlock->ptr_wblocked, writer, 389 pt_sleep); 390 } 391 #ifdef ERRORCHECK 392 } else { 393 pthread_spinunlock(self, &rwlock->ptr_interlock); 394 return EPERM; 395 #endif 396 } 397 398 if (writer != NULL) 399 pthread__unpark(self, &rwlock->ptr_interlock, 400 &rwlock->ptr_wblocked, writer); 401 else 402 pthread__unpark_all(self, &rwlock->ptr_interlock, 403 &rwlock->ptr_rblocked); 404 405 return 0; 406 } 407 408 409 int 410 pthread_rwlockattr_init(pthread_rwlockattr_t *attr) 411 { 412 #ifdef ERRORCHECK 413 if (attr == NULL) 414 return EINVAL; 415 #endif 416 attr->ptra_magic = _PT_RWLOCKATTR_MAGIC; 417 418 return 0; 419 } 420 421 422 int 423 pthread_rwlockattr_destroy(pthread_rwlockattr_t *attr) 424 { 425 #ifdef ERRORCHECK 426 if ((attr == NULL) || 427 (attr->ptra_magic != _PT_RWLOCKATTR_MAGIC)) 428 return EINVAL; 429 #endif 430 attr->ptra_magic = _PT_RWLOCKATTR_DEAD; 431 432 return 0; 433 } 434
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