pthread_lock.c revision 1.18
1 /* $NetBSD: pthread_lock.c,v 1.18 2007/03/02 18:53:52 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 1.18 2007/03/02 18:53:52 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 /* This does not belong here. */ 59 #if defined(i386) || defined(__x86_64__) 60 #define smt_pause() __asm __volatile("rep; nop" ::: "memory") 61 #else 62 #define smt_pause() /* nothing */ 63 #endif 64 65 extern int pthread__nspins; 66 67 RAS_DECL(pthread__lock); 68 69 static void 70 pthread__ras_simple_lock_init(__cpu_simple_lock_t *alp) 71 { 72 73 *alp = __SIMPLELOCK_UNLOCKED; 74 } 75 76 static int 77 pthread__ras_simple_lock_try(__cpu_simple_lock_t *alp) 78 { 79 __cpu_simple_lock_t old; 80 81 RAS_START(pthread__lock); 82 old = *alp; 83 *alp = __SIMPLELOCK_LOCKED; 84 RAS_END(pthread__lock); 85 86 return (old == __SIMPLELOCK_UNLOCKED); 87 } 88 89 static void 90 pthread__ras_simple_unlock(__cpu_simple_lock_t *alp) 91 { 92 93 *alp = __SIMPLELOCK_UNLOCKED; 94 } 95 96 static const struct pthread_lock_ops pthread__lock_ops_ras = { 97 pthread__ras_simple_lock_init, 98 pthread__ras_simple_lock_try, 99 pthread__ras_simple_unlock, 100 }; 101 102 static void 103 pthread__atomic_simple_lock_init(__cpu_simple_lock_t *alp) 104 { 105 106 __cpu_simple_lock_init(alp); 107 } 108 109 static int 110 pthread__atomic_simple_lock_try(__cpu_simple_lock_t *alp) 111 { 112 113 return (__cpu_simple_lock_try(alp)); 114 } 115 116 static void 117 pthread__atomic_simple_unlock(__cpu_simple_lock_t *alp) 118 { 119 120 __cpu_simple_unlock(alp); 121 } 122 123 static const struct pthread_lock_ops pthread__lock_ops_atomic = { 124 pthread__atomic_simple_lock_init, 125 pthread__atomic_simple_lock_try, 126 pthread__atomic_simple_unlock, 127 }; 128 129 /* 130 * We default to pointing to the RAS primitives; we might need to use 131 * locks early, but before main() starts. This is safe, since no other 132 * threads will be active for the process, so atomicity will not be 133 * required. 134 */ 135 const struct pthread_lock_ops *pthread__lock_ops = &pthread__lock_ops_ras; 136 137 /* 138 * Initialize the locking primitives. On uniprocessors, we always 139 * use Restartable Atomic Sequences if they are available. Otherwise, 140 * we fall back onto machine-dependent atomic lock primitives. 141 */ 142 void 143 pthread__lockprim_init(int ncpu) 144 { 145 146 if (ncpu == 1 && rasctl(RAS_ADDR(pthread__lock), 147 RAS_SIZE(pthread__lock), RAS_INSTALL) == 0) { 148 pthread__lock_ops = &pthread__lock_ops_ras; 149 return; 150 } 151 152 pthread__lock_ops = &pthread__lock_ops_atomic; 153 } 154 155 void 156 pthread_lockinit(pthread_spin_t *lock) 157 { 158 159 pthread__simple_lock_init(lock); 160 } 161 162 void 163 pthread_spinlock(pthread_t thread, pthread_spin_t *lock) 164 { 165 int count, ret; 166 167 count = pthread__nspins; 168 SDPRINTF(("(pthread_spinlock %p) incrementing spinlock %p (count %d)\n", 169 thread, lock, thread->pt_spinlocks)); 170 #ifdef PTHREAD_SPIN_DEBUG 171 pthread__assert(thread->pt_spinlocks >= 0); 172 #endif 173 ++thread->pt_spinlocks; 174 175 do { 176 while (((ret = pthread__simple_lock_try(lock)) == 0) && --count) { 177 smt_pause(); 178 } 179 180 if (ret == 1) 181 break; 182 183 SDPRINTF(("(pthread_spinlock %p) decrementing spinlock %p (count %d)\n", 184 thread, lock, thread->pt_spinlocks)); 185 --thread->pt_spinlocks; 186 187 /* 188 * We may be preempted while spinning. If so, we will 189 * be restarted here if thread->pt_spinlocks is 190 * nonzero, which can happen if: 191 * a) we just got the lock 192 * b) we haven't yet decremented the lock count. 193 * If we're at this point, (b) applies. Therefore, 194 * check if we're being continued, and if so, bail. 195 * (in case (a), we should let the code finish and 196 * we will bail out in pthread_spinunlock()). 197 */ 198 /* XXXLWP far from ideal */ 199 sched_yield(); 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)); 219 220 ++thread->pt_spinlocks; 221 ret = pthread__simple_lock_try(lock); 222 if (!ret) 223 --thread->pt_spinlocks; 224 return ret; 225 } 226 227 228 void 229 pthread_spinunlock(pthread_t thread, pthread_spin_t *lock) 230 { 231 232 pthread__simple_unlock(lock); 233 SDPRINTF(("(pthread_spinunlock %p) decrementing spinlock %p (count %d)\n", 234 thread, lock, thread->pt_spinlocks)); 235 --thread->pt_spinlocks; 236 #ifdef PTHREAD_SPIN_DEBUG 237 pthread__assert(thread->pt_spinlocks >= 0); 238 #endif 239 PTHREADD_ADD(PTHREADD_SPINUNLOCKS); 240 } 241 242 243 /* 244 * Public (POSIX-specified) spinlocks. 245 * These don't interact with the spin-preemption code, nor do they 246 * perform any adaptive sleeping. 247 */ 248 249 int 250 pthread_spin_init(pthread_spinlock_t *lock, int pshared) 251 { 252 253 #ifdef ERRORCHECK 254 if ((lock == NULL) || 255 ((pshared != PTHREAD_PROCESS_PRIVATE) && 256 (pshared != PTHREAD_PROCESS_SHARED))) 257 return EINVAL; 258 #endif 259 lock->pts_magic = _PT_SPINLOCK_MAGIC; 260 /* 261 * We don't actually use the pshared flag for anything; 262 * CPU simple locks have all the process-shared properties 263 * that we want anyway. 264 */ 265 lock->pts_flags = pshared; 266 pthread_lockinit(&lock->pts_spin); 267 268 return 0; 269 } 270 271 int 272 pthread_spin_destroy(pthread_spinlock_t *lock) 273 { 274 275 #ifdef ERRORCHECK 276 if ((lock == NULL) || (lock->pts_magic != _PT_SPINLOCK_MAGIC)) 277 return EINVAL; 278 279 if (lock->pts_spin != __SIMPLELOCK_UNLOCKED) 280 return EBUSY; 281 #endif 282 283 lock->pts_magic = _PT_SPINLOCK_DEAD; 284 285 return 0; 286 } 287 288 int 289 pthread_spin_lock(pthread_spinlock_t *lock) 290 { 291 292 #ifdef ERRORCHECK 293 if ((lock == NULL) || (lock->pts_magic != _PT_SPINLOCK_MAGIC)) 294 return EINVAL; 295 #endif 296 297 while (pthread__simple_lock_try(&lock->pts_spin) == 0) { 298 smt_pause(); 299 } 300 301 return 0; 302 } 303 304 int 305 pthread_spin_trylock(pthread_spinlock_t *lock) 306 { 307 308 #ifdef ERRORCHECK 309 if ((lock == NULL) || (lock->pts_magic != _PT_SPINLOCK_MAGIC)) 310 return EINVAL; 311 #endif 312 313 if (pthread__simple_lock_try(&lock->pts_spin) == 0) 314 return EBUSY; 315 316 return 0; 317 } 318 319 int 320 pthread_spin_unlock(pthread_spinlock_t *lock) 321 { 322 323 #ifdef ERRORCHECK 324 if ((lock == NULL) || (lock->pts_magic != _PT_SPINLOCK_MAGIC)) 325 return EINVAL; 326 #endif 327 328 pthread__simple_unlock(&lock->pts_spin); 329 330 return 0; 331 } 332
Indexes created Mon Sep 22 13:09:51 GMT 2025