pthread_lock.c revision 1.26
1 /* $NetBSD: pthread_lock.c,v 1.26 2007/09/07 14:09:27 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 1.26 2007/09/07 14:09:27 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 PTHREADD_ADD(PTHREADD_SPINLOCKS); 128 #endif 129 130 if (pthread__atomic) { 131 if (__predict_true(__cpu_simple_lock_try(lock))) 132 return; 133 } else { 134 __cpu_simple_lock_t old; 135 136 RAS_START(pthread__lock2); 137 old = *lock; 138 *lock = __SIMPLELOCK_LOCKED; 139 RAS_END(pthread__lock2); 140 141 if (__predict_true(old == __SIMPLELOCK_UNLOCKED)) 142 return; 143 } 144 145 pthread_spinlock_slow(lock); 146 } 147 148 /* 149 * Prevent this routine from being inlined. The common case is no 150 * contention and it's better to not burden the instruction decoder. 151 */ 152 #if __GNUC_PREREQ__(3, 0) 153 __attribute ((noinline)) 154 #endif 155 static void 156 pthread_spinlock_slow(pthread_spin_t *lock) 157 { 158 int count; 159 #ifdef PTHREAD_SPIN_DEBUG 160 pthread_t thread = pthread__self(); 161 #endif 162 163 do { 164 count = pthread__nspins; 165 while (*lock == __SIMPLELOCK_LOCKED && --count > 0) 166 pthread__smt_pause(); 167 if (count > 0) { 168 if (pthread__simple_lock_try(lock)) 169 break; 170 continue; 171 } 172 173 #ifdef PTHREAD_SPIN_DEBUG 174 SDPRINTF(("(pthread_spinlock %p) retrying spinlock %p " 175 "(count %d)\n", thread, lock, 176 thread->pt_spinlocks)); 177 thread->pt_spinlocks--; 178 /* XXXLWP far from ideal */ 179 sched_yield(); 180 thread->pt_spinlocks++; 181 #else 182 /* XXXLWP far from ideal */ 183 sched_yield(); 184 #endif 185 } while (/*CONSTCOND*/ 1); 186 } 187 188 int 189 pthread_spintrylock(pthread_spin_t *lock) 190 { 191 #ifdef PTHREAD_SPIN_DEBUG 192 pthread_t thread = pthread__self(); 193 int ret; 194 195 SDPRINTF(("(pthread_spintrylock %p) spinlock %p (count %d)\n", 196 thread, lock, thread->pt_spinlocks)); 197 thread->pt_spinlocks++; 198 ret = pthread__simple_lock_try(lock); 199 if (!ret) 200 thread->pt_spinlocks--; 201 return ret; 202 #else 203 return pthread__simple_lock_try(lock); 204 #endif 205 } 206 207 void 208 pthread_spinunlock(pthread_spin_t *lock) 209 { 210 #ifdef PTHREAD_SPIN_DEBUG 211 pthread_t thread = pthread__self(); 212 213 SDPRINTF(("(pthread_spinunlock %p) spinlock %p (count %d)\n", 214 thread, lock, thread->pt_spinlocks)); 215 216 pthread__simple_unlock(lock); 217 thread->pt_spinlocks--; 218 pthread__assert(thread->pt_spinlocks >= 0); 219 PTHREADD_ADD(PTHREADD_SPINUNLOCKS); 220 #else 221 pthread__simple_unlock(lock); 222 #endif 223 } 224 225 /* 226 * Initialize the locking primitives. On uniprocessors, we always 227 * use Restartable Atomic Sequences if they are available. Otherwise, 228 * we fall back onto machine-dependent atomic lock primitives. 229 */ 230 void 231 pthread__lockprim_init(void) 232 { 233 char *p; 234 235 if ((p = getenv("PTHREAD_NSPINS")) != NULL) 236 pthread__nspins = atoi(p); 237 else if (pthread__concurrency != 1) 238 pthread__nspins = PTHREAD__NSPINS; 239 else 240 pthread__nspins = 1; 241 242 if (pthread__concurrency != 1) { 243 pthread__atomic = 1; 244 return; 245 } 246 247 if (rasctl(RAS_ADDR(pthread__lock), RAS_SIZE(pthread__lock), 248 RAS_INSTALL) != 0) { 249 pthread__atomic = 1; 250 return; 251 } 252 253 if (rasctl(RAS_ADDR(pthread__lock2), RAS_SIZE(pthread__lock2), 254 RAS_INSTALL) != 0) { 255 pthread__atomic = 1; 256 return; 257 } 258 } 259 260 void 261 pthread_lockinit(pthread_spin_t *lock) 262 { 263 264 pthread__simple_lock_init(lock); 265 } 266
Indexes created Sun Sep 21 20:09:37 GMT 2025