pthread_lock.c revision 1.25
1 /* $NetBSD: pthread_lock.c,v 1.25 2007/09/07 00:07:54 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 /* 40 * libpthread internal spinlock routines. 41 */ 42 43 #include <sys/cdefs.h> 44 __RCSID("$NetBSD: pthread_lock.c,v 1.25 2007/09/07 00:07:54 ad Exp $"); 45 46 #include <sys/types.h> 47 #include <sys/lock.h> 48 #include <sys/ras.h> 49 50 #include <errno.h> 51 #include <unistd.h> 52 #include <stdio.h> 53 #include <stdlib.h> 54 #include <time.h> 55 56 #include "pthread.h" 57 #include "pthread_int.h" 58 59 /* How many times to try acquiring spin locks on MP systems. */ 60 #define PTHREAD__NSPINS 1024 61 62 #ifdef PTHREAD_SPIN_DEBUG_PRINT 63 #define SDPRINTF(x) DPRINTF(x) 64 #else 65 #define SDPRINTF(x) 66 #endif 67 68 static void pthread_spinlock_slow(pthread_spin_t *); 69 70 static int pthread__atomic; 71 72 RAS_DECL(pthread__lock); 73 RAS_DECL(pthread__lock2); 74 75 void 76 pthread__simple_lock_init(__cpu_simple_lock_t *alp) 77 { 78 79 if (pthread__atomic) { 80 __cpu_simple_lock_init(alp); 81 return; 82 } 83 84 *alp = __SIMPLELOCK_UNLOCKED; 85 } 86 87 int 88 pthread__simple_lock_try(__cpu_simple_lock_t *alp) 89 { 90 __cpu_simple_lock_t old; 91 92 if (pthread__atomic) 93 return __cpu_simple_lock_try(alp); 94 95 RAS_START(pthread__lock); 96 old = *alp; 97 *alp = __SIMPLELOCK_LOCKED; 98 RAS_END(pthread__lock); 99 100 return old == __SIMPLELOCK_UNLOCKED; 101 } 102 103 inline void 104 pthread__simple_unlock(__cpu_simple_lock_t *alp) 105 { 106 107 #ifdef PTHREAD__CHEAP_UNLOCK 108 __cpu_simple_unlock(alp); 109 #else 110 if (pthread__atomic) { 111 __cpu_simple_unlock(alp); 112 return; 113 } 114 *alp = __SIMPLELOCK_UNLOCKED; 115 #endif 116 } 117 118 void 119 pthread_spinlock(pthread_spin_t *lock) 120 { 121 #ifdef PTHREAD_SPIN_DEBUG 122 pthread_t thread = pthread__self(); 123 124 SDPRINTF(("(pthread_spinlock %p) spinlock %p (count %d)\n", 125 thread, lock, thread->pt_spinlocks)); 126 pthread__assert(thread->pt_spinlocks >= 0); 127 thread->pt_spinlocks++; 128 PTHREADD_ADD(PTHREADD_SPINLOCKS); 129 #endif 130 131 if (pthread__atomic) { 132 if (__predict_true(__cpu_simple_lock_try(lock))) 133 return; 134 } else { 135 __cpu_simple_lock_t old; 136 137 RAS_START(pthread__lock2); 138 old = *lock; 139 *lock = __SIMPLELOCK_LOCKED; 140 RAS_END(pthread__lock2); 141 142 if (__predict_true(old == __SIMPLELOCK_UNLOCKED)) 143 return; 144 } 145 146 pthread_spinlock_slow(lock); 147 } 148 149 /* 150 * Prevent this routine from being inlined. The common case is no 151 * contention and it's better to not burden the instruction decoder. 152 */ 153 #if __GNUC_PREREQ__(3, 0) 154 __attribute ((noinline)) 155 #endif 156 static void 157 pthread_spinlock_slow(pthread_spin_t *lock) 158 { 159 struct timespec ts; 160 int count; 161 #ifdef PTHREAD_SPIN_DEBUG 162 pthread_t thread = pthread__self(); 163 #endif 164 165 do { 166 count = pthread__nspins; 167 while (*lock == __SIMPLELOCK_LOCKED && --count > 0) 168 pthread__smt_pause(); 169 if (count > 0) { 170 if (pthread__simple_lock_try(lock)) 171 break; 172 continue; 173 } 174 175 #ifdef PTHREAD_SPIN_DEBUG 176 SDPRINTF(("(pthread_spinlock %p) retrying spinlock %p " 177 "(count %d)\n", thread, lock, 178 thread->pt_spinlocks)); 179 thread->pt_spinlocks--; 180 ts.tv_sec = 0; 181 ts.tv_nsec = 1; 182 nanosleep(&ts, NULL); 183 thread->pt_spinlocks++; 184 #else 185 ts.tv_sec = 0; 186 ts.tv_nsec = 1; 187 nanosleep(&ts, NULL); 188 #endif 189 } while (/*CONSTCOND*/ 1); 190 } 191 192 int 193 pthread_spintrylock(pthread_spin_t *lock) 194 { 195 #ifdef PTHREAD_SPIN_DEBUG 196 pthread_t thread = pthread__self(); 197 int ret; 198 199 SDPRINTF(("(pthread_spintrylock %p) spinlock %p (count %d)\n", 200 thread, lock, thread->pt_spinlocks)); 201 thread->pt_spinlocks++; 202 ret = pthread__simple_lock_try(lock); 203 if (!ret) 204 thread->pt_spinlocks--; 205 return ret; 206 #else 207 return pthread__simple_lock_try(lock); 208 #endif 209 } 210 211 void 212 pthread_spinunlock(pthread_spin_t *lock) 213 { 214 #ifdef PTHREAD_SPIN_DEBUG 215 pthread_t thread = pthread__self(); 216 217 SDPRINTF(("(pthread_spinunlock %p) spinlock %p (count %d)\n", 218 thread, lock, thread->pt_spinlocks)); 219 220 pthread__simple_unlock(lock); 221 thread->pt_spinlocks--; 222 pthread__assert(thread->pt_spinlocks >= 0); 223 PTHREADD_ADD(PTHREADD_SPINUNLOCKS); 224 #else 225 pthread__simple_unlock(lock); 226 #endif 227 } 228 229 /* 230 * Initialize the locking primitives. On uniprocessors, we always 231 * use Restartable Atomic Sequences if they are available. Otherwise, 232 * we fall back onto machine-dependent atomic lock primitives. 233 */ 234 void 235 pthread__lockprim_init(void) 236 { 237 char *p; 238 239 if ((p = getenv("PTHREAD_NSPINS")) != NULL) 240 pthread__nspins = atoi(p); 241 else if (pthread__concurrency != 1) 242 pthread__nspins = PTHREAD__NSPINS; 243 else 244 pthread__nspins = 1; 245 246 if (pthread__concurrency != 1) { 247 pthread__atomic = 1; 248 return; 249 } 250 251 if (rasctl(RAS_ADDR(pthread__lock), RAS_SIZE(pthread__lock), 252 RAS_INSTALL) != 0) { 253 pthread__atomic = 1; 254 return; 255 } 256 257 if (rasctl(RAS_ADDR(pthread__lock2), RAS_SIZE(pthread__lock2), 258 RAS_INSTALL) != 0) { 259 pthread__atomic = 1; 260 return; 261 } 262 } 263 264 void 265 pthread_lockinit(pthread_spin_t *lock) 266 { 267 268 pthread__simple_lock_init(lock); 269 } 270
Indexes created Sun Sep 21 16:09:51 GMT 2025