pthread_lock.c revision 1.23
1 /* $NetBSD: pthread_lock.c,v 1.23 2007/08/16 13:54:17 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 1.23 2007/08/16 13:54:17 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 55 #include "pthread.h" 56 #include "pthread_int.h" 57 58 /* How many times to try acquiring spin locks on MP systems. */ 59 #define PTHREAD__NSPINS 1024 60 61 #ifdef PTHREAD_SPIN_DEBUG_PRINT 62 #define SDPRINTF(x) DPRINTF(x) 63 #else 64 #define SDPRINTF(x) 65 #endif 66 67 static void pthread_spinlock_slow(pthread_spin_t *); 68 69 static int pthread__atomic; 70 71 RAS_DECL(pthread__lock); 72 RAS_DECL(pthread__lock2); 73 74 void 75 pthread__simple_lock_init(__cpu_simple_lock_t *alp) 76 { 77 78 if (pthread__atomic) { 79 __cpu_simple_lock_init(alp); 80 return; 81 } 82 83 *alp = __SIMPLELOCK_UNLOCKED; 84 } 85 86 int 87 pthread__simple_lock_try(__cpu_simple_lock_t *alp) 88 { 89 __cpu_simple_lock_t old; 90 91 if (pthread__atomic) 92 return __cpu_simple_lock_try(alp); 93 94 RAS_START(pthread__lock); 95 old = *alp; 96 *alp = __SIMPLELOCK_LOCKED; 97 RAS_END(pthread__lock); 98 99 return old == __SIMPLELOCK_UNLOCKED; 100 } 101 102 inline void 103 pthread__simple_unlock(__cpu_simple_lock_t *alp) 104 { 105 106 #ifdef PTHREAD__CHEAP_UNLOCK 107 __cpu_simple_unlock(alp); 108 #else 109 if (pthread__atomic) { 110 __cpu_simple_unlock(alp); 111 return; 112 } 113 *alp = __SIMPLELOCK_UNLOCKED; 114 #endif 115 } 116 117 void 118 pthread_spinlock(pthread_spin_t *lock) 119 { 120 #ifdef PTHREAD_SPIN_DEBUG 121 pthread_t thread = pthread__self(); 122 123 SDPRINTF(("(pthread_spinlock %p) spinlock %p (count %d)\n", 124 thread, lock, thread->pt_spinlocks)); 125 pthread__assert(thread->pt_spinlocks >= 0); 126 thread->pt_spinlocks++; 127 #endif 128 129 if (pthread__atomic) { 130 if (__predict_false(!__cpu_simple_lock_try(lock))) { 131 pthread_spinlock_slow(lock); 132 return; 133 } 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_false(old != __SIMPLELOCK_UNLOCKED)) { 143 pthread_spinlock_slow(lock); 144 return; 145 } 146 } 147 148 PTHREADD_ADD(PTHREADD_SPINLOCKS); 149 } 150 151 /* 152 * Prevent this routine from being inlined. The common case is no 153 * contention and it's better to not burden the instruction decoder. 154 */ 155 #if __GNUC_PREREQ__(3, 0) 156 __attribute ((noinline)) 157 #endif 158 static void 159 pthread_spinlock_slow(pthread_spin_t *lock) 160 { 161 int count; 162 #ifdef PTHREAD_SPIN_DEBUG 163 pthread_t thread = pthread__self(); 164 #endif 165 166 do { 167 count = pthread__nspins; 168 while (*lock == __SIMPLELOCK_LOCKED && --count > 0) 169 pthread__smt_pause(); 170 if (count > 0) { 171 if (pthread__simple_lock_try(lock)) 172 break; 173 continue; 174 } 175 176 #ifdef PTHREAD_SPIN_DEBUG 177 SDPRINTF(("(pthread_spinlock %p) retrying spinlock %p " 178 "(count %d)\n", thread, lock, 179 thread->pt_spinlocks)); 180 thread->pt_spinlocks--; 181 /* XXXLWP far from ideal */ 182 sched_yield(); 183 thread->pt_spinlocks++; 184 #else 185 /* XXXLWP far from ideal */ 186 sched_yield(); 187 #endif 188 } while (/*CONSTCOND*/ 1); 189 190 PTHREADD_ADD(PTHREADD_SPINLOCKS); 191 } 192 193 int 194 pthread_spintrylock(pthread_spin_t *lock) 195 { 196 #ifdef PTHREAD_SPIN_DEBUG 197 pthread_t thread = pthread__self(); 198 int ret; 199 200 SDPRINTF(("(pthread_spintrylock %p) spinlock %p (count %d)\n", 201 thread, lock, thread->pt_spinlocks)); 202 thread->pt_spinlocks++; 203 ret = pthread__simple_lock_try(lock); 204 if (!ret) 205 thread->pt_spinlocks--; 206 return ret; 207 #else 208 return pthread__simple_lock_try(lock); 209 #endif 210 } 211 212 void 213 pthread_spinunlock(pthread_spin_t *lock) 214 { 215 #ifdef PTHREAD_SPIN_DEBUG 216 pthread_t thread = pthread__self(); 217 218 SDPRINTF(("(pthread_spinunlock %p) spinlock %p (count %d)\n", 219 thread, lock, thread->pt_spinlocks)); 220 221 pthread__simple_unlock(lock); 222 thread->pt_spinlocks--; 223 pthread__assert(thread->pt_spinlocks >= 0); 224 PTHREADD_ADD(PTHREADD_SPINUNLOCKS); 225 #else 226 pthread__simple_unlock(lock); 227 #endif 228 } 229 230 /* 231 * Initialize the locking primitives. On uniprocessors, we always 232 * use Restartable Atomic Sequences if they are available. Otherwise, 233 * we fall back onto machine-dependent atomic lock primitives. 234 */ 235 void 236 pthread__lockprim_init(void) 237 { 238 char *p; 239 240 if ((p = getenv("PTHREAD_NSPINS")) != NULL) 241 pthread__nspins = atoi(p); 242 else if (pthread__concurrency != 1) 243 pthread__nspins = PTHREAD__NSPINS; 244 else 245 pthread__nspins = 1; 246 247 if (pthread__concurrency != 1) { 248 pthread__atomic = 1; 249 return; 250 } 251 252 if (rasctl(RAS_ADDR(pthread__lock), RAS_SIZE(pthread__lock), 253 RAS_INSTALL) != 0) { 254 pthread__atomic = 1; 255 return; 256 } 257 258 if (rasctl(RAS_ADDR(pthread__lock2), RAS_SIZE(pthread__lock2), 259 RAS_INSTALL) != 0) { 260 pthread__atomic = 1; 261 return; 262 } 263 } 264 265 void 266 pthread_lockinit(pthread_spin_t *lock) 267 { 268 269 pthread__simple_lock_init(lock); 270 } 271
Indexes created Tue Sep 23 07:09:52 GMT 2025