pthread_lock.c revision 1.20.2.4
1 /* $NetBSD: pthread_lock.c,v 1.20.2.4 2007/09/03 10:14:15 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 /* 40 * libpthread internal spinlock routines. 41 */ 42 43 #include <sys/cdefs.h> 44 __RCSID("$NetBSD: pthread_lock.c,v 1.20.2.4 2007/09/03 10:14:15 skrll 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 int 75 pthread__simple_locked_p(__cpu_simple_lock_t *alp) 76 { 77 return __SIMPLELOCK_LOCKED_P(alp); 78 } 79 80 void 81 pthread__simple_lock_init(__cpu_simple_lock_t *alp) 82 { 83 84 if (pthread__atomic) { 85 __cpu_simple_lock_init(alp); 86 return; 87 } 88 89 __cpu_simple_lock_clear(alp); 90 } 91 92 int 93 pthread__simple_lock_try(__cpu_simple_lock_t *alp) 94 { 95 int unlocked; 96 97 if (pthread__atomic) 98 return __cpu_simple_lock_try(alp); 99 100 RAS_START(pthread__lock); 101 unlocked = __SIMPLELOCK_UNLOCKED_P(alp); 102 __cpu_simple_lock_set(alp); 103 RAS_END(pthread__lock); 104 105 return unlocked; 106 } 107 108 inline void 109 pthread__simple_unlock(__cpu_simple_lock_t *alp) 110 { 111 112 #ifdef PTHREAD__CHEAP_UNLOCK 113 __cpu_simple_unlock(alp); 114 #else 115 if (pthread__atomic) { 116 __cpu_simple_unlock(alp); 117 return; 118 } 119 120 __cpu_simple_lock_clear(alp); 121 #endif 122 } 123 124 void 125 pthread_spinlock(pthread_spin_t *lock) 126 { 127 #ifdef PTHREAD_SPIN_DEBUG 128 pthread_t thread = pthread__self(); 129 130 SDPRINTF(("(pthread_spinlock %p) spinlock %p (count %d)\n", 131 thread, lock, thread->pt_spinlocks)); 132 pthread__assert(thread->pt_spinlocks >= 0); 133 thread->pt_spinlocks++; 134 PTHREADD_ADD(PTHREADD_SPINLOCKS); 135 #endif 136 137 if (pthread__atomic) { 138 if (__predict_true(__cpu_simple_lock_try(lock))) 139 return; 140 } else { 141 int unlocked; 142 143 RAS_START(pthread__lock2); 144 unlocked = __SIMPLELOCK_UNLOCKED_P(lock); 145 __cpu_simple_lock_set(lock); 146 RAS_END(pthread__lock2); 147 148 if (__predict_true(unlocked)) 149 return; 150 } 151 152 pthread_spinlock_slow(lock); 153 } 154 155 /* 156 * Prevent this routine from being inlined. The common case is no 157 * contention and it's better to not burden the instruction decoder. 158 */ 159 #if __GNUC_PREREQ__(3, 0) 160 __attribute ((noinline)) 161 #endif 162 static void 163 pthread_spinlock_slow(pthread_spin_t *lock) 164 { 165 int count; 166 #ifdef PTHREAD_SPIN_DEBUG 167 pthread_t thread = pthread__self(); 168 #endif 169 170 do { 171 count = pthread__nspins; 172 while (pthread__simple_locked_p(lock) && --count > 0) 173 pthread__smt_pause(); 174 if (count > 0) { 175 if (pthread__simple_lock_try(lock)) 176 break; 177 continue; 178 } 179 180 #ifdef PTHREAD_SPIN_DEBUG 181 SDPRINTF(("(pthread_spinlock %p) retrying spinlock %p " 182 "(count %d)\n", thread, lock, 183 thread->pt_spinlocks)); 184 thread->pt_spinlocks--; 185 /* XXXLWP far from ideal */ 186 sched_yield(); 187 thread->pt_spinlocks++; 188 #else 189 /* XXXLWP far from ideal */ 190 sched_yield(); 191 #endif 192 } while (/*CONSTCOND*/ 1); 193 } 194 195 int 196 pthread_spintrylock(pthread_spin_t *lock) 197 { 198 #ifdef PTHREAD_SPIN_DEBUG 199 pthread_t thread = pthread__self(); 200 int ret; 201 202 SDPRINTF(("(pthread_spintrylock %p) spinlock %p (count %d)\n", 203 thread, lock, thread->pt_spinlocks)); 204 thread->pt_spinlocks++; 205 ret = pthread__simple_lock_try(lock); 206 if (!ret) 207 thread->pt_spinlocks--; 208 return ret; 209 #else 210 return pthread__simple_lock_try(lock); 211 #endif 212 } 213 214 void 215 pthread_spinunlock(pthread_spin_t *lock) 216 { 217 #ifdef PTHREAD_SPIN_DEBUG 218 pthread_t thread = pthread__self(); 219 220 SDPRINTF(("(pthread_spinunlock %p) spinlock %p (count %d)\n", 221 thread, lock, thread->pt_spinlocks)); 222 223 pthread__simple_unlock(lock); 224 thread->pt_spinlocks--; 225 pthread__assert(thread->pt_spinlocks >= 0); 226 PTHREADD_ADD(PTHREADD_SPINUNLOCKS); 227 #else 228 pthread__simple_unlock(lock); 229 #endif 230 } 231 232 /* 233 * Initialize the locking primitives. On uniprocessors, we always 234 * use Restartable Atomic Sequences if they are available. Otherwise, 235 * we fall back onto machine-dependent atomic lock primitives. 236 */ 237 void 238 pthread__lockprim_init(void) 239 { 240 char *p; 241 242 if ((p = getenv("PTHREAD_NSPINS")) != NULL) 243 pthread__nspins = atoi(p); 244 else if (pthread__concurrency != 1) 245 pthread__nspins = PTHREAD__NSPINS; 246 else 247 pthread__nspins = 1; 248 249 if (pthread__concurrency != 1) { 250 pthread__atomic = 1; 251 return; 252 } 253 254 if (rasctl(RAS_ADDR(pthread__lock), RAS_SIZE(pthread__lock), 255 RAS_INSTALL) != 0) { 256 pthread__atomic = 1; 257 return; 258 } 259 260 if (rasctl(RAS_ADDR(pthread__lock2), RAS_SIZE(pthread__lock2), 261 RAS_INSTALL) != 0) { 262 pthread__atomic = 1; 263 return; 264 } 265 } 266 267 void 268 pthread_lockinit(pthread_spin_t *lock) 269 { 270 271 pthread__simple_lock_init(lock); 272 } 273
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