pthread_lock.c revision 1.16
1 /* $NetBSD: pthread_lock.c,v 1.16 2006/12/24 18:39:46 ad Exp $ */ 2 3 /*- 4 * Copyright (c) 2001 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_lock.c,v 1.16 2006/12/24 18:39:46 ad Exp $"); 41 42 #include <sys/types.h> 43 #include <sys/lock.h> 44 #include <sys/ras.h> 45 46 #include <errno.h> 47 #include <unistd.h> 48 49 #include "pthread.h" 50 #include "pthread_int.h" 51 52 #ifdef PTHREAD_SPIN_DEBUG_PRINT 53 #define SDPRINTF(x) DPRINTF(x) 54 #else 55 #define SDPRINTF(x) 56 #endif 57 58 extern int pthread__nspins; 59 60 RAS_DECL(pthread__lock); 61 62 static void 63 pthread__ras_simple_lock_init(__cpu_simple_lock_t *alp) 64 { 65 66 *alp = __SIMPLELOCK_UNLOCKED; 67 } 68 69 static int 70 pthread__ras_simple_lock_try(__cpu_simple_lock_t *alp) 71 { 72 __cpu_simple_lock_t old; 73 74 RAS_START(pthread__lock); 75 old = *alp; 76 *alp = __SIMPLELOCK_LOCKED; 77 RAS_END(pthread__lock); 78 79 return (old == __SIMPLELOCK_UNLOCKED); 80 } 81 82 static void 83 pthread__ras_simple_unlock(__cpu_simple_lock_t *alp) 84 { 85 86 *alp = __SIMPLELOCK_UNLOCKED; 87 } 88 89 static const struct pthread_lock_ops pthread__lock_ops_ras = { 90 pthread__ras_simple_lock_init, 91 pthread__ras_simple_lock_try, 92 pthread__ras_simple_unlock, 93 }; 94 95 static void 96 pthread__atomic_simple_lock_init(__cpu_simple_lock_t *alp) 97 { 98 99 __cpu_simple_lock_init(alp); 100 } 101 102 static int 103 pthread__atomic_simple_lock_try(__cpu_simple_lock_t *alp) 104 { 105 106 return (__cpu_simple_lock_try(alp)); 107 } 108 109 static void 110 pthread__atomic_simple_unlock(__cpu_simple_lock_t *alp) 111 { 112 113 __cpu_simple_unlock(alp); 114 } 115 116 static const struct pthread_lock_ops pthread__lock_ops_atomic = { 117 pthread__atomic_simple_lock_init, 118 pthread__atomic_simple_lock_try, 119 pthread__atomic_simple_unlock, 120 }; 121 122 /* 123 * We default to pointing to the RAS primitives; we might need to use 124 * locks early, but before main() starts. This is safe, since no other 125 * threads will be active for the process, so atomicity will not be 126 * required. 127 */ 128 const struct pthread_lock_ops *pthread__lock_ops = &pthread__lock_ops_ras; 129 130 /* 131 * Initialize the locking primitives. On uniprocessors, we always 132 * use Restartable Atomic Sequences if they are available. Otherwise, 133 * we fall back onto machine-dependent atomic lock primitives. 134 */ 135 void 136 pthread__lockprim_init(int ncpu) 137 { 138 139 if (ncpu == 1 && rasctl(RAS_ADDR(pthread__lock), 140 RAS_SIZE(pthread__lock), RAS_INSTALL) == 0) { 141 pthread__lock_ops = &pthread__lock_ops_ras; 142 return; 143 } 144 145 pthread__lock_ops = &pthread__lock_ops_atomic; 146 } 147 148 void 149 pthread_lockinit(pthread_spin_t *lock) 150 { 151 152 pthread__simple_lock_init(lock); 153 } 154 155 void 156 pthread_spinlock(pthread_t thread, pthread_spin_t *lock) 157 { 158 int count, ret; 159 160 count = pthread__nspins; 161 SDPRINTF(("(pthread_spinlock %p) incrementing spinlock %p (count %d)\n", 162 thread, lock, thread->pt_spinlocks)); 163 #ifdef PTHREAD_SPIN_DEBUG 164 pthread__assert(thread->pt_spinlocks >= 0); 165 #endif 166 ++thread->pt_spinlocks; 167 168 do { 169 while (((ret = pthread__simple_lock_try(lock)) == 0) && --count) 170 /* XXX For at least x86, issue 'pause' instruction */; 171 172 if (ret == 1) 173 break; 174 175 SDPRINTF(("(pthread_spinlock %p) decrementing spinlock %p (count %d)\n", 176 thread, lock, thread->pt_spinlocks)); 177 --thread->pt_spinlocks; 178 179 /* 180 * We may be preempted while spinning. If so, we will 181 * be restarted here if thread->pt_spinlocks is 182 * nonzero, which can happen if: 183 * a) we just got the lock 184 * b) we haven't yet decremented the lock count. 185 * If we're at this point, (b) applies. Therefore, 186 * check if we're being continued, and if so, bail. 187 * (in case (a), we should let the code finish and 188 * we will bail out in pthread_spinunlock()). 189 */ 190 #ifdef PTHREAD_SA 191 if (thread->pt_next != NULL) { 192 PTHREADD_ADD(PTHREADD_SPINPREEMPT); 193 pthread__assert(thread->pt_blockgen == thread->pt_unblockgen); 194 pthread__switch(thread, thread->pt_next); 195 } 196 #else 197 /* XXXLWP far from ideal */ 198 sched_yield(); 199 #endif 200 /* try again */ 201 count = pthread__nspins; 202 SDPRINTF(("(pthread_spinlock %p) incrementing spinlock from %d\n", 203 thread, thread->pt_spinlocks)); 204 ++thread->pt_spinlocks; 205 } while (/*CONSTCOND*/1); 206 207 PTHREADD_ADD(PTHREADD_SPINLOCKS); 208 /* Got it! We're out of here. */ 209 } 210 211 212 int 213 pthread_spintrylock(pthread_t thread, pthread_spin_t *lock) 214 { 215 int ret; 216 217 SDPRINTF(("(pthread_spinlock %p) incrementing spinlock from %d\n", 218 thread, thread->pt_spinlocks)); 219 ++thread->pt_spinlocks; 220 221 ret = pthread__simple_lock_try(lock); 222 223 #ifdef PTHREAD_SA 224 if (ret == 0) { 225 SDPRINTF(("(pthread_spintrylock %p) decrementing spinlock from %d\n", 226 thread, thread->pt_spinlocks)); 227 --thread->pt_spinlocks; 228 /* See above. */ 229 if (thread->pt_next != NULL) { 230 PTHREADD_ADD(PTHREADD_SPINPREEMPT); 231 pthread__assert(thread->pt_blockgen == thread->pt_unblockgen); 232 pthread__switch(thread, thread->pt_next); 233 } 234 } 235 #endif 236 237 return ret; 238 } 239 240 241 void 242 pthread_spinunlock(pthread_t thread, pthread_spin_t *lock) 243 { 244 245 pthread__simple_unlock(lock); 246 SDPRINTF(("(pthread_spinunlock %p) decrementing spinlock %p (count %d)\n", 247 thread, lock, thread->pt_spinlocks)); 248 --thread->pt_spinlocks; 249 #ifdef PTHREAD_SPIN_DEBUG 250 pthread__assert(thread->pt_spinlocks >= 0); 251 #endif 252 PTHREADD_ADD(PTHREADD_SPINUNLOCKS); 253 254 #ifdef PTHREAD_SA 255 /* 256 * If we were preempted while holding a spinlock, the 257 * scheduler will notice this and continue us. To be good 258 * citzens, we must now get out of here if that was our 259 * last spinlock. 260 * XXX when will we ever have more than one? 261 */ 262 263 if ((thread->pt_spinlocks == 0) && (thread->pt_next != NULL)) { 264 PTHREADD_ADD(PTHREADD_SPINPREEMPT); 265 /* pthread__assert(thread->pt_blockgen == thread->pt_unblockgen); */ 266 pthread__switch(thread, thread->pt_next); 267 } 268 #endif 269 } 270 271 272 /* 273 * Public (POSIX-specified) spinlocks. 274 * These don't interact with the spin-preemption code, nor do they 275 * perform any adaptive sleeping. 276 */ 277 278 int 279 pthread_spin_init(pthread_spinlock_t *lock, int pshared) 280 { 281 282 #ifdef ERRORCHECK 283 if ((lock == NULL) || 284 ((pshared != PTHREAD_PROCESS_PRIVATE) && 285 (pshared != PTHREAD_PROCESS_SHARED))) 286 return EINVAL; 287 #endif 288 lock->pts_magic = _PT_SPINLOCK_MAGIC; 289 /* 290 * We don't actually use the pshared flag for anything; 291 * CPU simple locks have all the process-shared properties 292 * that we want anyway. 293 */ 294 lock->pts_flags = pshared; 295 pthread_lockinit(&lock->pts_spin); 296 297 return 0; 298 } 299 300 int 301 pthread_spin_destroy(pthread_spinlock_t *lock) 302 { 303 304 #ifdef ERRORCHECK 305 if ((lock == NULL) || (lock->pts_magic != _PT_SPINLOCK_MAGIC)) 306 return EINVAL; 307 308 if (lock->pts_spin != __SIMPLELOCK_UNLOCKED) 309 return EBUSY; 310 #endif 311 312 lock->pts_magic = _PT_SPINLOCK_DEAD; 313 314 return 0; 315 } 316 317 int 318 pthread_spin_lock(pthread_spinlock_t *lock) 319 { 320 321 #ifdef ERRORCHECK 322 if ((lock == NULL) || (lock->pts_magic != _PT_SPINLOCK_MAGIC)) 323 return EINVAL; 324 #endif 325 326 while (pthread__simple_lock_try(&lock->pts_spin) == 0) 327 /* spin */ ; 328 329 return 0; 330 } 331 332 int 333 pthread_spin_trylock(pthread_spinlock_t *lock) 334 { 335 336 #ifdef ERRORCHECK 337 if ((lock == NULL) || (lock->pts_magic != _PT_SPINLOCK_MAGIC)) 338 return EINVAL; 339 #endif 340 341 if (pthread__simple_lock_try(&lock->pts_spin) == 0) 342 return EBUSY; 343 344 return 0; 345 } 346 347 int 348 pthread_spin_unlock(pthread_spinlock_t *lock) 349 { 350 351 #ifdef ERRORCHECK 352 if ((lock == NULL) || (lock->pts_magic != _PT_SPINLOCK_MAGIC)) 353 return EINVAL; 354 #endif 355 356 pthread__simple_unlock(&lock->pts_spin); 357 358 return 0; 359 } 360
Indexes created Tue Sep 23 01:09:51 GMT 2025