pthread_lock.c revision 1.3
1 /* $NetBSD: pthread_lock.c,v 1.3 2003/01/18 18:45:55 christos 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/param.h> 40 #include <sys/ras.h> 41 #include <sys/sysctl.h> 42 43 #include <assert.h> 44 #include <errno.h> 45 #include <unistd.h> 46 47 #include "pthread.h" 48 #include "pthread_int.h" 49 50 #undef PTHREAD_SPIN_DEBUG 51 52 #ifdef PTHREAD_SPIN_DEBUG 53 #define SDPRINTF(x) DPRINTF(x) 54 #else 55 #define SDPRINTF(x) 56 #endif 57 58 /* How many times to try before checking whether we've been continued. */ 59 #define NSPINS 1 /* no point in actually spinning until MP works */ 60 61 static int nspins = NSPINS; 62 63 extern char pthread__lock_ras_start[], pthread__lock_ras_end[]; 64 65 static void 66 pthread__ras_simple_lock_init(__cpu_simple_lock_t *alp) 67 { 68 69 *alp = __SIMPLELOCK_UNLOCKED; 70 } 71 72 static int 73 pthread__ras_simple_lock_try(__cpu_simple_lock_t *alp) 74 { 75 __cpu_simple_lock_t old; 76 77 /* This is the atomic sequence. */ 78 __asm __volatile("pthread__lock_ras_start:"); 79 old = *alp; 80 *alp = __SIMPLELOCK_LOCKED; 81 __asm __volatile("pthread__lock_ras_end:"); 82 83 return (old == __SIMPLELOCK_UNLOCKED); 84 } 85 86 static void 87 pthread__ras_simple_unlock(__cpu_simple_lock_t *alp) 88 { 89 90 *alp = __SIMPLELOCK_UNLOCKED; 91 } 92 93 static const struct pthread_lock_ops pthread__lock_ops_ras = { 94 pthread__ras_simple_lock_init, 95 pthread__ras_simple_lock_try, 96 pthread__ras_simple_unlock, 97 }; 98 99 static void 100 pthread__atomic_simple_lock_init(__cpu_simple_lock_t *alp) 101 { 102 103 __cpu_simple_lock_init(alp); 104 } 105 106 static int 107 pthread__atomic_simple_lock_try(__cpu_simple_lock_t *alp) 108 { 109 110 return (__cpu_simple_lock_try(alp)); 111 } 112 113 static void 114 pthread__atomic_simple_unlock(__cpu_simple_lock_t *alp) 115 { 116 117 __cpu_simple_unlock(alp); 118 } 119 120 static const struct pthread_lock_ops pthread__lock_ops_atomic = { 121 pthread__atomic_simple_lock_init, 122 pthread__atomic_simple_lock_try, 123 pthread__atomic_simple_unlock, 124 }; 125 126 /* 127 * We default to pointing to the RAS primitives; we might need to use 128 * locks early, but before main() starts. This is safe, since no other 129 * threads will be active for the process, so atomicity will not be 130 * required. 131 */ 132 const struct pthread_lock_ops *pthread__lock_ops = &pthread__lock_ops_ras; 133 134 /* 135 * Initialize the locking primitives. On uniprocessors, we always 136 * use Restartable Atomic Sequences if they are available. Otherwise, 137 * we fall back onto machine-dependent atomic lock primitives. 138 */ 139 void 140 pthread__lockprim_init(void) 141 { 142 int mib[2]; 143 size_t len; 144 int ncpu; 145 146 mib[0] = CTL_HW; 147 mib[1] = HW_NCPU; 148 149 len = sizeof(ncpu); 150 sysctl(mib, 2, &ncpu, &len, NULL, 0); 151 152 if (ncpu == 1 && rasctl(pthread__lock_ras_start, 153 (size_t)(pthread__lock_ras_end - pthread__lock_ras_start), 154 RAS_INSTALL) == 0) { 155 pthread__lock_ops = &pthread__lock_ops_ras; 156 return; 157 } 158 159 pthread__lock_ops = &pthread__lock_ops_atomic; 160 } 161 162 void 163 pthread_lockinit(pthread_spin_t *lock) 164 { 165 166 pthread__simple_lock_init(lock); 167 } 168 169 void 170 pthread_spinlock(pthread_t thread, pthread_spin_t *lock) 171 { 172 int count, ret; 173 174 count = nspins; 175 SDPRINTF(("(pthread_spinlock %p) incrementing spinlock %p (count %d)\n", 176 thread, lock, thread->pt_spinlocks)); 177 #ifdef PTHREAD_SPIN_DEBUG 178 if(!(thread->pt_spinlocks >= 0)) { 179 (void)kill(getpid(), SIGABRT); 180 _exit(1); 181 } 182 #endif 183 ++thread->pt_spinlocks; 184 185 do { 186 while (((ret = pthread__simple_lock_try(lock)) == 0) && --count) 187 ; 188 189 if (ret == 1) 190 break; 191 192 SDPRINTF(("(pthread_spinlock %p) decrementing spinlock %p (count %d)\n", 193 thread, lock, thread->pt_spinlocks)); 194 --thread->pt_spinlocks; 195 196 /* 197 * We may be preempted while spinning. If so, we will 198 * be restarted here if thread->pt_spinlocks is 199 * nonzero, which can happen if: 200 * a) we just got the lock 201 * b) we haven't yet decremented the lock count. 202 * If we're at this point, (b) applies. Therefore, 203 * check if we're being continued, and if so, bail. 204 * (in case (a), we should let the code finish and 205 * we will bail out in pthread_spinunlock()). 206 */ 207 if (thread->pt_next != NULL) { 208 PTHREADD_ADD(PTHREADD_SPINPREEMPT); 209 pthread__switch(thread, thread->pt_next); 210 } 211 /* try again */ 212 count = nspins; 213 SDPRINTF(("(pthread_spinlock %p) incrementing spinlock from %d\n", 214 thread, thread->pt_spinlocks)); 215 ++thread->pt_spinlocks; 216 } while (/*CONSTCOND*/1); 217 218 PTHREADD_ADD(PTHREADD_SPINLOCKS); 219 /* Got it! We're out of here. */ 220 } 221 222 223 int 224 pthread_spintrylock(pthread_t thread, pthread_spin_t *lock) 225 { 226 int ret; 227 228 SDPRINTF(("(pthread_spinlock %p) incrementing spinlock from %d\n", 229 thread, thread->pt_spinlocks)); 230 ++thread->pt_spinlocks; 231 232 ret = pthread__simple_lock_try(lock); 233 234 if (ret == 0) { 235 SDPRINTF(("(pthread_spintrylock %p) decrementing spinlock from %d\n", 236 thread, thread->pt_spinlocks)); 237 --thread->pt_spinlocks; 238 /* See above. */ 239 if (thread->pt_next != NULL) { 240 PTHREADD_ADD(PTHREADD_SPINPREEMPT); 241 pthread__switch(thread, thread->pt_next); 242 } 243 } 244 245 return ret; 246 } 247 248 249 void 250 pthread_spinunlock(pthread_t thread, pthread_spin_t *lock) 251 { 252 253 pthread__simple_unlock(lock); 254 SDPRINTF(("(pthread_spinunlock %p) decrementing spinlock %p (count %d)\n", 255 thread, lock, thread->pt_spinlocks)); 256 --thread->pt_spinlocks; 257 #ifdef PTHREAD_SPIN_DEBUG 258 if (!(thread->pt_spinlocks >= 0)) { 259 (void)kill(getpid(), SIGABRT); 260 _exit(1); 261 } 262 #endif 263 PTHREADD_ADD(PTHREADD_SPINUNLOCKS); 264 265 /* 266 * If we were preempted while holding a spinlock, the 267 * scheduler will notice this and continue us. To be good 268 * citzens, we must now get out of here if that was our 269 * last spinlock. 270 * XXX when will we ever have more than one? 271 */ 272 273 if ((thread->pt_spinlocks == 0) && (thread->pt_next != NULL)) { 274 PTHREADD_ADD(PTHREADD_SPINPREEMPT); 275 pthread__switch(thread, thread->pt_next); 276 } 277 } 278 279 280 /* 281 * Public (POSIX-specified) spinlocks. 282 * These don't interact with the spin-preemption code, nor do they 283 * perform any adaptive sleeping. 284 */ 285 286 int 287 pthread_spin_init(pthread_spinlock_t *lock, int pshared) 288 { 289 290 #ifdef ERRORCHECK 291 if ((lock == NULL) || 292 ((pshared != PTHREAD_PROCESS_PRIVATE) && 293 (pshared != PTHREAD_PROCESS_SHARED))) 294 return EINVAL; 295 #endif 296 lock->pts_magic = _PT_SPINLOCK_MAGIC; 297 /* 298 * We don't actually use the pshared flag for anything; 299 * cpu simple locks have all the process-shared properties 300 * that we want anyway. 301 */ 302 lock->pts_flags = pshared; 303 pthread_lockinit(&lock->pts_spin); 304 305 return 0; 306 } 307 308 int 309 pthread_spin_destroy(pthread_spinlock_t *lock) 310 { 311 312 #ifdef ERRORCHECK 313 if ((lock == NULL) || (lock->pts_magic != _PT_SPINLOCK_MAGIC)) 314 return EINVAL; 315 316 if (lock->pts_spin != __SIMPLELOCK_UNLOCKED) 317 return EBUSY; 318 #endif 319 320 lock->pts_magic = _PT_SPINLOCK_DEAD; 321 322 return 0; 323 } 324 325 int 326 pthread_spin_lock(pthread_spinlock_t *lock) 327 { 328 329 #ifdef ERRORCHECK 330 if ((lock == NULL) || (lock->pts_magic != _PT_SPINLOCK_MAGIC)) 331 return EINVAL; 332 #endif 333 334 while (pthread__simple_lock_try(&lock->pts_spin) == 0) 335 /* spin */ ; 336 337 return 0; 338 } 339 340 int 341 pthread_spin_trylock(pthread_spinlock_t *lock) 342 { 343 344 #ifdef ERRORCHECK 345 if ((lock == NULL) || (lock->pts_magic != _PT_SPINLOCK_MAGIC)) 346 return EINVAL; 347 #endif 348 349 if (pthread__simple_lock_try(&lock->pts_spin) == 0) 350 return EBUSY; 351 352 return 0; 353 } 354 355 int 356 pthread_spin_unlock(pthread_spinlock_t *lock) 357 { 358 359 #ifdef ERRORCHECK 360 if ((lock == NULL) || (lock->pts_magic != _PT_SPINLOCK_MAGIC)) 361 return EINVAL; 362 #endif 363 364 pthread__simple_unlock(&lock->pts_spin); 365 366 return 0; 367 } 368
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