pthread_lock.c revision 1.11
1 /* $NetBSD: pthread_lock.c,v 1.11 2004/03/14 01:19:42 cl Exp $ */ 2 3 /*- 4 * Copyright (c) 2001 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. 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 1.11 2004/03/14 01:19:42 cl Exp $"); 41 42 #include <sys/lock.h> 43 #include <sys/ras.h> 44 45 #include <errno.h> 46 #include <unistd.h> 47 48 #include "pthread.h" 49 #include "pthread_int.h" 50 51 #ifdef PTHREAD_SPIN_DEBUG_PRINT 52 #define SDPRINTF(x) DPRINTF(x) 53 #else 54 #define SDPRINTF(x) 55 #endif 56 57 /* How many times to try before checking whether we've been continued. */ 58 #define NSPINS 1000 /* no point in actually spinning until MP works */ 59 60 static int nspins = NSPINS; 61 62 RAS_DECL(pthread__lock); 63 64 static void 65 pthread__ras_simple_lock_init(__cpu_simple_lock_t *alp) 66 { 67 68 *alp = __SIMPLELOCK_UNLOCKED; 69 } 70 71 static int 72 pthread__ras_simple_lock_try(__cpu_simple_lock_t *alp) 73 { 74 __cpu_simple_lock_t old; 75 76 RAS_START(pthread__lock); 77 old = *alp; 78 *alp = __SIMPLELOCK_LOCKED; 79 RAS_END(pthread__lock); 80 81 return (old == __SIMPLELOCK_UNLOCKED); 82 } 83 84 static void 85 pthread__ras_simple_unlock(__cpu_simple_lock_t *alp) 86 { 87 88 *alp = __SIMPLELOCK_UNLOCKED; 89 } 90 91 static const struct pthread_lock_ops pthread__lock_ops_ras = { 92 pthread__ras_simple_lock_init, 93 pthread__ras_simple_lock_try, 94 pthread__ras_simple_unlock, 95 }; 96 97 static void 98 pthread__atomic_simple_lock_init(__cpu_simple_lock_t *alp) 99 { 100 101 __cpu_simple_lock_init(alp); 102 } 103 104 static int 105 pthread__atomic_simple_lock_try(__cpu_simple_lock_t *alp) 106 { 107 108 return (__cpu_simple_lock_try(alp)); 109 } 110 111 static void 112 pthread__atomic_simple_unlock(__cpu_simple_lock_t *alp) 113 { 114 115 __cpu_simple_unlock(alp); 116 } 117 118 static const struct pthread_lock_ops pthread__lock_ops_atomic = { 119 pthread__atomic_simple_lock_init, 120 pthread__atomic_simple_lock_try, 121 pthread__atomic_simple_unlock, 122 }; 123 124 /* 125 * We default to pointing to the RAS primitives; we might need to use 126 * locks early, but before main() starts. This is safe, since no other 127 * threads will be active for the process, so atomicity will not be 128 * required. 129 */ 130 const struct pthread_lock_ops *pthread__lock_ops = &pthread__lock_ops_ras; 131 132 /* 133 * Initialize the locking primitives. On uniprocessors, we always 134 * use Restartable Atomic Sequences if they are available. Otherwise, 135 * we fall back onto machine-dependent atomic lock primitives. 136 */ 137 void 138 pthread__lockprim_init(int ncpu) 139 { 140 141 if (ncpu == 1 && rasctl(RAS_ADDR(pthread__lock), 142 RAS_SIZE(pthread__lock), RAS_INSTALL) == 0) { 143 pthread__lock_ops = &pthread__lock_ops_ras; 144 return; 145 } 146 147 pthread__lock_ops = &pthread__lock_ops_atomic; 148 } 149 150 void 151 pthread_lockinit(pthread_spin_t *lock) 152 { 153 154 pthread__simple_lock_init(lock); 155 } 156 157 void 158 pthread_spinlock(pthread_t thread, pthread_spin_t *lock) 159 { 160 int count, ret; 161 162 count = nspins; 163 SDPRINTF(("(pthread_spinlock %p) incrementing spinlock %p (count %d)\n", 164 thread, lock, thread->pt_spinlocks)); 165 #ifdef PTHREAD_SPIN_DEBUG 166 pthread__assert(thread->pt_spinlocks >= 0); 167 #endif 168 ++thread->pt_spinlocks; 169 170 do { 171 while (((ret = pthread__simple_lock_try(lock)) == 0) && --count) 172 ; 173 174 if (ret == 1) 175 break; 176 177 SDPRINTF(("(pthread_spinlock %p) decrementing spinlock %p (count %d)\n", 178 thread, lock, thread->pt_spinlocks)); 179 --thread->pt_spinlocks; 180 181 /* 182 * We may be preempted while spinning. If so, we will 183 * be restarted here if thread->pt_spinlocks is 184 * nonzero, which can happen if: 185 * a) we just got the lock 186 * b) we haven't yet decremented the lock count. 187 * If we're at this point, (b) applies. Therefore, 188 * check if we're being continued, and if so, bail. 189 * (in case (a), we should let the code finish and 190 * we will bail out in pthread_spinunlock()). 191 */ 192 if (thread->pt_next != NULL) { 193 PTHREADD_ADD(PTHREADD_SPINPREEMPT); 194 pthread__switch(thread, thread->pt_next); 195 } 196 /* try again */ 197 count = nspins; 198 SDPRINTF(("(pthread_spinlock %p) incrementing spinlock from %d\n", 199 thread, thread->pt_spinlocks)); 200 ++thread->pt_spinlocks; 201 } while (/*CONSTCOND*/1); 202 203 PTHREADD_ADD(PTHREADD_SPINLOCKS); 204 /* Got it! We're out of here. */ 205 } 206 207 208 int 209 pthread_spintrylock(pthread_t thread, pthread_spin_t *lock) 210 { 211 int ret; 212 213 SDPRINTF(("(pthread_spinlock %p) incrementing spinlock from %d\n", 214 thread, thread->pt_spinlocks)); 215 ++thread->pt_spinlocks; 216 217 ret = pthread__simple_lock_try(lock); 218 219 if (ret == 0) { 220 SDPRINTF(("(pthread_spintrylock %p) decrementing spinlock from %d\n", 221 thread, thread->pt_spinlocks)); 222 --thread->pt_spinlocks; 223 /* See above. */ 224 if (thread->pt_next != NULL) { 225 PTHREADD_ADD(PTHREADD_SPINPREEMPT); 226 pthread__switch(thread, thread->pt_next); 227 } 228 } 229 230 return ret; 231 } 232 233 234 void 235 pthread_spinunlock(pthread_t thread, pthread_spin_t *lock) 236 { 237 238 pthread__simple_unlock(lock); 239 SDPRINTF(("(pthread_spinunlock %p) decrementing spinlock %p (count %d)\n", 240 thread, lock, thread->pt_spinlocks)); 241 --thread->pt_spinlocks; 242 #ifdef PTHREAD_SPIN_DEBUG 243 pthread__assert(thread->pt_spinlocks >= 0); 244 #endif 245 PTHREADD_ADD(PTHREADD_SPINUNLOCKS); 246 247 /* 248 * If we were preempted while holding a spinlock, the 249 * scheduler will notice this and continue us. To be good 250 * citzens, we must now get out of here if that was our 251 * last spinlock. 252 * XXX when will we ever have more than one? 253 */ 254 255 if ((thread->pt_spinlocks == 0) && (thread->pt_next != NULL)) { 256 PTHREADD_ADD(PTHREADD_SPINPREEMPT); 257 pthread__switch(thread, thread->pt_next); 258 } 259 } 260 261 262 /* 263 * Public (POSIX-specified) spinlocks. 264 * These don't interact with the spin-preemption code, nor do they 265 * perform any adaptive sleeping. 266 */ 267 268 int 269 pthread_spin_init(pthread_spinlock_t *lock, int pshared) 270 { 271 272 #ifdef ERRORCHECK 273 if ((lock == NULL) || 274 ((pshared != PTHREAD_PROCESS_PRIVATE) && 275 (pshared != PTHREAD_PROCESS_SHARED))) 276 return EINVAL; 277 #endif 278 lock->pts_magic = _PT_SPINLOCK_MAGIC; 279 /* 280 * We don't actually use the pshared flag for anything; 281 * CPU simple locks have all the process-shared properties 282 * that we want anyway. 283 */ 284 lock->pts_flags = pshared; 285 pthread_lockinit(&lock->pts_spin); 286 287 return 0; 288 } 289 290 int 291 pthread_spin_destroy(pthread_spinlock_t *lock) 292 { 293 294 #ifdef ERRORCHECK 295 if ((lock == NULL) || (lock->pts_magic != _PT_SPINLOCK_MAGIC)) 296 return EINVAL; 297 298 if (lock->pts_spin != __SIMPLELOCK_UNLOCKED) 299 return EBUSY; 300 #endif 301 302 lock->pts_magic = _PT_SPINLOCK_DEAD; 303 304 return 0; 305 } 306 307 int 308 pthread_spin_lock(pthread_spinlock_t *lock) 309 { 310 311 #ifdef ERRORCHECK 312 if ((lock == NULL) || (lock->pts_magic != _PT_SPINLOCK_MAGIC)) 313 return EINVAL; 314 #endif 315 316 while (pthread__simple_lock_try(&lock->pts_spin) == 0) 317 /* spin */ ; 318 319 return 0; 320 } 321 322 int 323 pthread_spin_trylock(pthread_spinlock_t *lock) 324 { 325 326 #ifdef ERRORCHECK 327 if ((lock == NULL) || (lock->pts_magic != _PT_SPINLOCK_MAGIC)) 328 return EINVAL; 329 #endif 330 331 if (pthread__simple_lock_try(&lock->pts_spin) == 0) 332 return EBUSY; 333 334 return 0; 335 } 336 337 int 338 pthread_spin_unlock(pthread_spinlock_t *lock) 339 { 340 341 #ifdef ERRORCHECK 342 if ((lock == NULL) || (lock->pts_magic != _PT_SPINLOCK_MAGIC)) 343 return EINVAL; 344 #endif 345 346 pthread__simple_unlock(&lock->pts_spin); 347 348 return 0; 349 } 350
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