pthread_lock.c revision 1.21
1 /* $NetBSD: pthread_lock.c,v 1.21 2007/08/04 13:37:49 ad 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 1.21 2007/08/04 13:37:49 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 #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 static int pthread__atomic; 60 61 RAS_DECL(pthread__lock); 62 63 void 64 pthread__simple_lock_init(__cpu_simple_lock_t *alp) 65 { 66 67 if (pthread__atomic) { 68 __cpu_simple_lock_init(alp); 69 return; 70 } 71 72 *alp = __SIMPLELOCK_UNLOCKED; 73 } 74 75 int 76 pthread__simple_lock_try(__cpu_simple_lock_t *alp) 77 { 78 __cpu_simple_lock_t old; 79 80 if (pthread__atomic) 81 return __cpu_simple_lock_try(alp); 82 83 RAS_START(pthread__lock); 84 old = *alp; 85 *alp = __SIMPLELOCK_LOCKED; 86 RAS_END(pthread__lock); 87 88 return old == __SIMPLELOCK_UNLOCKED; 89 } 90 91 inline void 92 pthread__simple_unlock(__cpu_simple_lock_t *alp) 93 { 94 95 if (pthread__atomic) { 96 __cpu_simple_unlock(alp); 97 return; 98 } 99 100 *alp = __SIMPLELOCK_UNLOCKED; 101 } 102 103 /* 104 * Initialize the locking primitives. On uniprocessors, we always 105 * use Restartable Atomic Sequences if they are available. Otherwise, 106 * we fall back onto machine-dependent atomic lock primitives. 107 */ 108 void 109 pthread__lockprim_init(int ncpu) 110 { 111 112 if (ncpu != 1) { 113 pthread__atomic = 1; 114 return; 115 } 116 117 if (rasctl(RAS_ADDR(pthread__lock), RAS_SIZE(pthread__lock), 118 RAS_INSTALL) != 0) { 119 pthread__atomic = 1; 120 return; 121 } 122 } 123 124 void 125 pthread_lockinit(pthread_spin_t *lock) 126 { 127 128 pthread__simple_lock_init(lock); 129 } 130 131 void 132 pthread_spinlock(pthread_t thread, pthread_spin_t *lock) 133 { 134 int count; 135 136 SDPRINTF(("(pthread_spinlock %p) spinlock %p (count %d)\n", 137 thread, lock, thread->pt_spinlocks)); 138 #ifdef PTHREAD_SPIN_DEBUG 139 pthread__assert(thread->pt_spinlocks >= 0); 140 #endif 141 142 thread->pt_spinlocks++; 143 if (__predict_true(pthread__simple_lock_try(lock))) { 144 PTHREADD_ADD(PTHREADD_SPINLOCKS); 145 return; 146 } 147 148 do { 149 count = pthread__nspins; 150 while (*lock == __SIMPLELOCK_LOCKED && --count > 0) 151 pthread__smt_pause(); 152 if (count > 0) { 153 if (pthread__simple_lock_try(lock)) 154 break; 155 continue; 156 } 157 158 SDPRINTF(("(pthread_spinlock %p) retrying spinlock %p " 159 "(count %d)\n", thread, lock, 160 thread->pt_spinlocks)); 161 thread->pt_spinlocks--; 162 163 /* XXXLWP far from ideal */ 164 sched_yield(); 165 thread->pt_spinlocks++; 166 } while (/*CONSTCOND*/ 1); 167 168 PTHREADD_ADD(PTHREADD_SPINLOCKS); 169 } 170 171 int 172 pthread_spintrylock(pthread_t thread, pthread_spin_t *lock) 173 { 174 int ret; 175 176 SDPRINTF(("(pthread_spintrylock %p) spinlock %p (count %d)\n", 177 thread, lock, thread->pt_spinlocks)); 178 179 thread->pt_spinlocks++; 180 ret = pthread__simple_lock_try(lock); 181 if (!ret) 182 thread->pt_spinlocks--; 183 184 return ret; 185 } 186 187 void 188 pthread_spinunlock(pthread_t thread, pthread_spin_t *lock) 189 { 190 191 SDPRINTF(("(pthread_spinunlock %p) spinlock %p (count %d)\n", 192 thread, lock, thread->pt_spinlocks)); 193 194 pthread__simple_unlock(lock); 195 thread->pt_spinlocks--; 196 #ifdef PTHREAD_SPIN_DEBUG 197 pthread__assert(thread->pt_spinlocks >= 0); 198 #endif 199 PTHREADD_ADD(PTHREADD_SPINUNLOCKS); 200 } 201 202 203 /* 204 * Public (POSIX-specified) spinlocks. 205 */ 206 int 207 pthread_spin_init(pthread_spinlock_t *lock, int pshared) 208 { 209 210 #ifdef ERRORCHECK 211 if (lock == NULL || (pshared != PTHREAD_PROCESS_PRIVATE && 212 pshared != PTHREAD_PROCESS_SHARED)) 213 return EINVAL; 214 #endif 215 lock->pts_magic = _PT_SPINLOCK_MAGIC; 216 217 /* 218 * We don't actually use the pshared flag for anything; 219 * CPU simple locks have all the process-shared properties 220 * that we want anyway. 221 */ 222 lock->pts_flags = pshared; 223 pthread_lockinit(&lock->pts_spin); 224 225 return 0; 226 } 227 228 int 229 pthread_spin_destroy(pthread_spinlock_t *lock) 230 { 231 232 #ifdef ERRORCHECK 233 if (lock == NULL || lock->pts_magic != _PT_SPINLOCK_MAGIC) 234 return EINVAL; 235 if (lock->pts_spin != __SIMPLELOCK_UNLOCKED) 236 return EBUSY; 237 #endif 238 239 lock->pts_magic = _PT_SPINLOCK_DEAD; 240 241 return 0; 242 } 243 244 int 245 pthread_spin_lock(pthread_spinlock_t *lock) 246 { 247 248 #ifdef ERRORCHECK 249 if (lock == NULL || lock->pts_magic != _PT_SPINLOCK_MAGIC) 250 return EINVAL; 251 #endif 252 253 while (pthread__simple_lock_try(&lock->pts_spin) == 0) { 254 pthread__smt_pause(); 255 } 256 257 return 0; 258 } 259 260 int 261 pthread_spin_trylock(pthread_spinlock_t *lock) 262 { 263 264 #ifdef ERRORCHECK 265 if (lock == NULL || lock->pts_magic != _PT_SPINLOCK_MAGIC) 266 return EINVAL; 267 #endif 268 269 if (pthread__simple_lock_try(&lock->pts_spin) == 0) 270 return EBUSY; 271 272 return 0; 273 } 274 275 int 276 pthread_spin_unlock(pthread_spinlock_t *lock) 277 { 278 279 #ifdef ERRORCHECK 280 if (lock == NULL || lock->pts_magic != _PT_SPINLOCK_MAGIC) 281 return EINVAL; 282 #endif 283 284 pthread__simple_unlock(&lock->pts_spin); 285 286 return 0; 287 } 288
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