pthread_lock.c revision 1.20.2.2
1 /* $NetBSD: pthread_lock.c,v 1.20.2.2 2007/08/15 08:25:10 skrll Exp $ */ 2 3 /*- 4 * Copyright (c) 2001, 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_lock.c,v 1.20.2.2 2007/08/15 08:25:10 skrll 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 #include <stdio.h> 49 50 #include "pthread.h" 51 #include "pthread_int.h" 52 53 #ifdef PTHREAD_SPIN_DEBUG_PRINT 54 #define SDPRINTF(x) DPRINTF(x) 55 #else 56 #define SDPRINTF(x) 57 #endif 58 59 /* This does not belong here. */ 60 #if defined(i386) || defined(__x86_64__) 61 #define smt_pause() __asm __volatile("rep; nop" ::: "memory") 62 #else 63 #define smt_pause() /* nothing */ 64 #endif 65 66 extern int pthread__nspins; 67 static int pthread__atomic; 68 69 RAS_DECL(pthread__lock); 70 71 void 72 pthread__simple_lock_init(__cpu_simple_lock_t *alp) 73 { 74 75 if (pthread__atomic) { 76 __cpu_simple_lock_init(alp); 77 return; 78 } 79 80 __cpu_simple_lock_clear(alp); 81 } 82 83 int 84 pthread__simple_lock_try(__cpu_simple_lock_t *alp) 85 { 86 int unlocked; 87 88 if (pthread__atomic) 89 return __cpu_simple_lock_try(alp); 90 91 RAS_START(pthread__lock); 92 unlocked = __SIMPLELOCK_UNLOCKED_P(alp); 93 __cpu_simple_lock_set(alp); 94 RAS_END(pthread__lock); 95 96 return unlocked; 97 } 98 99 inline void 100 pthread__simple_unlock(__cpu_simple_lock_t *alp) 101 { 102 103 if (pthread__atomic) { 104 __cpu_simple_unlock(alp); 105 return; 106 } 107 108 __cpu_simple_lock_clear(alp); 109 } 110 111 /* 112 * Initialize the locking primitives. On uniprocessors, we always 113 * use Restartable Atomic Sequences if they are available. Otherwise, 114 * we fall back onto machine-dependent atomic lock primitives. 115 */ 116 void 117 pthread__lockprim_init(int ncpu) 118 { 119 120 if (ncpu != 1) { 121 pthread__atomic = 1; 122 return; 123 } 124 125 if (rasctl(RAS_ADDR(pthread__lock), RAS_SIZE(pthread__lock), 126 RAS_INSTALL) != 0) { 127 pthread__atomic = 1; 128 return; 129 } 130 } 131 132 void 133 pthread_lockinit(pthread_spin_t *lock) 134 { 135 136 pthread__simple_lock_init(lock); 137 } 138 139 void 140 pthread_spinlock(pthread_t thread, pthread_spin_t *lock) 141 { 142 int count, ret; 143 144 count = pthread__nspins; 145 SDPRINTF(("(pthread_spinlock %p) spinlock %p (count %d)\n", 146 thread, lock, thread->pt_spinlocks)); 147 #ifdef PTHREAD_SPIN_DEBUG 148 pthread__assert(thread->pt_spinlocks >= 0); 149 #endif 150 151 thread->pt_spinlocks++; 152 if (__predict_true(pthread__simple_lock_try(lock))) { 153 PTHREADD_ADD(PTHREADD_SPINLOCKS); 154 return; 155 } 156 157 do { 158 while ((ret = pthread__simple_lock_try(lock)) == 0 && 159 --count) { 160 smt_pause(); 161 } 162 163 if (ret == 1) 164 break; 165 166 SDPRINTF(("(pthread_spinlock %p) retrying spinlock %p " 167 "(count %d)\n", thread, lock, 168 thread->pt_spinlocks)); 169 thread->pt_spinlocks--; 170 171 /* XXXLWP far from ideal */ 172 sched_yield(); 173 count = pthread__nspins; 174 thread->pt_spinlocks++; 175 } while (/*CONSTCOND*/ 1); 176 177 PTHREADD_ADD(PTHREADD_SPINLOCKS); 178 } 179 180 int 181 pthread_spintrylock(pthread_t thread, pthread_spin_t *lock) 182 { 183 int ret; 184 185 SDPRINTF(("(pthread_spintrylock %p) spinlock %p (count %d)\n", 186 thread, lock, thread->pt_spinlocks)); 187 188 thread->pt_spinlocks++; 189 ret = pthread__simple_lock_try(lock); 190 if (!ret) 191 thread->pt_spinlocks--; 192 193 return ret; 194 } 195 196 void 197 pthread_spinunlock(pthread_t thread, pthread_spin_t *lock) 198 { 199 200 SDPRINTF(("(pthread_spinunlock %p) spinlock %p (count %d)\n", 201 thread, lock, thread->pt_spinlocks)); 202 203 pthread__simple_unlock(lock); 204 thread->pt_spinlocks--; 205 #ifdef PTHREAD_SPIN_DEBUG 206 pthread__assert(thread->pt_spinlocks >= 0); 207 #endif 208 PTHREADD_ADD(PTHREADD_SPINUNLOCKS); 209 } 210 211 212 /* 213 * Public (POSIX-specified) spinlocks. 214 */ 215 int 216 pthread_spin_init(pthread_spinlock_t *lock, int pshared) 217 { 218 219 #ifdef ERRORCHECK 220 if (lock == NULL || (pshared != PTHREAD_PROCESS_PRIVATE && 221 pshared != PTHREAD_PROCESS_SHARED)) 222 return EINVAL; 223 #endif 224 lock->pts_magic = _PT_SPINLOCK_MAGIC; 225 226 /* 227 * We don't actually use the pshared flag for anything; 228 * CPU simple locks have all the process-shared properties 229 * that we want anyway. 230 */ 231 lock->pts_flags = pshared; 232 pthread_lockinit(&lock->pts_spin); 233 234 return 0; 235 } 236 237 int 238 pthread_spin_destroy(pthread_spinlock_t *lock) 239 { 240 241 #ifdef ERRORCHECK 242 if (lock == NULL || lock->pts_magic != _PT_SPINLOCK_MAGIC) 243 return EINVAL; 244 if (!__SIMPLELOCK_UNLOCKED_P(&lock->pts_spin)) 245 return EBUSY; 246 #endif 247 248 lock->pts_magic = _PT_SPINLOCK_DEAD; 249 250 return 0; 251 } 252 253 int 254 pthread_spin_lock(pthread_spinlock_t *lock) 255 { 256 257 #ifdef ERRORCHECK 258 if (lock == NULL || lock->pts_magic != _PT_SPINLOCK_MAGIC) 259 return EINVAL; 260 #endif 261 262 while (pthread__simple_lock_try(&lock->pts_spin) == 0) { 263 smt_pause(); 264 } 265 266 return 0; 267 } 268 269 int 270 pthread_spin_trylock(pthread_spinlock_t *lock) 271 { 272 273 #ifdef ERRORCHECK 274 if (lock == NULL || lock->pts_magic != _PT_SPINLOCK_MAGIC) 275 return EINVAL; 276 #endif 277 278 if (pthread__simple_lock_try(&lock->pts_spin) == 0) 279 return EBUSY; 280 281 return 0; 282 } 283 284 int 285 pthread_spin_unlock(pthread_spinlock_t *lock) 286 { 287 288 #ifdef ERRORCHECK 289 if (lock == NULL || lock->pts_magic != _PT_SPINLOCK_MAGIC) 290 return EINVAL; 291 #endif 292 293 pthread__simple_unlock(&lock->pts_spin); 294 295 return 0; 296 } 297
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