pthread_lock.c revision 1.5
1 /* $NetBSD: pthread_lock.c,v 1.5 2003/02/15 04:37:04 nathanw 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 <errno.h> 44 #include <unistd.h> 45 46 #include "pthread.h" 47 #include "pthread_int.h" 48 49 #ifdef PTHREAD_SPIN_DEBUG_PRINT 50 #define SDPRINTF(x) DPRINTF(x) 51 #else 52 #define SDPRINTF(x) 53 #endif 54 55 /* How many times to try before checking whether we've been continued. */ 56 #define NSPINS 1 /* no point in actually spinning until MP works */ 57 58 static int nspins = NSPINS; 59 60 extern void pthread__lock_ras_start(void), pthread__lock_ras_end(void); 61 62 static void 63 pthread__ras_simple_lock_init(__cpu_simple_lock_t *alp) 64 { 65 66 *alp = __SIMPLELOCK_UNLOCKED; 67 } 68 69 static int 70 pthread__ras_simple_lock_try(__cpu_simple_lock_t *alp) 71 { 72 __cpu_simple_lock_t old; 73 74 /* This is the atomic sequence. */ 75 __asm __volatile("pthread__lock_ras_start:"); 76 old = *alp; 77 *alp = __SIMPLELOCK_LOCKED; 78 __asm __volatile("pthread__lock_ras_end:"); 79 80 return (old == __SIMPLELOCK_UNLOCKED); 81 } 82 83 static void 84 pthread__ras_simple_unlock(__cpu_simple_lock_t *alp) 85 { 86 87 *alp = __SIMPLELOCK_UNLOCKED; 88 } 89 90 static const struct pthread_lock_ops pthread__lock_ops_ras = { 91 pthread__ras_simple_lock_init, 92 pthread__ras_simple_lock_try, 93 pthread__ras_simple_unlock, 94 }; 95 96 static void 97 pthread__atomic_simple_lock_init(__cpu_simple_lock_t *alp) 98 { 99 100 __cpu_simple_lock_init(alp); 101 } 102 103 static int 104 pthread__atomic_simple_lock_try(__cpu_simple_lock_t *alp) 105 { 106 107 return (__cpu_simple_lock_try(alp)); 108 } 109 110 static void 111 pthread__atomic_simple_unlock(__cpu_simple_lock_t *alp) 112 { 113 114 __cpu_simple_unlock(alp); 115 } 116 117 static const struct pthread_lock_ops pthread__lock_ops_atomic = { 118 pthread__atomic_simple_lock_init, 119 pthread__atomic_simple_lock_try, 120 pthread__atomic_simple_unlock, 121 }; 122 123 /* 124 * We default to pointing to the RAS primitives; we might need to use 125 * locks early, but before main() starts. This is safe, since no other 126 * threads will be active for the process, so atomicity will not be 127 * required. 128 */ 129 const struct pthread_lock_ops *pthread__lock_ops = &pthread__lock_ops_ras; 130 131 /* 132 * Initialize the locking primitives. On uniprocessors, we always 133 * use Restartable Atomic Sequences if they are available. Otherwise, 134 * we fall back onto machine-dependent atomic lock primitives. 135 */ 136 void 137 pthread__lockprim_init(void) 138 { 139 int mib[2]; 140 size_t len; 141 int ncpu; 142 143 mib[0] = CTL_HW; 144 mib[1] = HW_NCPU; 145 146 len = sizeof(ncpu); 147 sysctl(mib, 2, &ncpu, &len, NULL, 0); 148 149 if (ncpu == 1 && rasctl((void *)pthread__lock_ras_start, 150 (size_t)((uintptr_t)pthread__lock_ras_end - 151 (uintptr_t)pthread__lock_ras_start), 152 RAS_INSTALL) == 0) { 153 pthread__lock_ops = &pthread__lock_ops_ras; 154 return; 155 } 156 157 pthread__lock_ops = &pthread__lock_ops_atomic; 158 } 159 160 void 161 pthread_lockinit(pthread_spin_t *lock) 162 { 163 164 pthread__simple_lock_init(lock); 165 } 166 167 void 168 pthread_spinlock(pthread_t thread, pthread_spin_t *lock) 169 { 170 int count, ret; 171 172 count = nspins; 173 SDPRINTF(("(pthread_spinlock %p) incrementing spinlock %p (count %d)\n", 174 thread, lock, thread->pt_spinlocks)); 175 #ifdef PTHREAD_SPIN_DEBUG 176 pthread__assert(thread->pt_spinlocks >= 0); 177 #endif 178 ++thread->pt_spinlocks; 179 180 do { 181 while (((ret = pthread__simple_lock_try(lock)) == 0) && --count) 182 ; 183 184 if (ret == 1) 185 break; 186 187 SDPRINTF(("(pthread_spinlock %p) decrementing spinlock %p (count %d)\n", 188 thread, lock, thread->pt_spinlocks)); 189 --thread->pt_spinlocks; 190 191 /* 192 * We may be preempted while spinning. If so, we will 193 * be restarted here if thread->pt_spinlocks is 194 * nonzero, which can happen if: 195 * a) we just got the lock 196 * b) we haven't yet decremented the lock count. 197 * If we're at this point, (b) applies. Therefore, 198 * check if we're being continued, and if so, bail. 199 * (in case (a), we should let the code finish and 200 * we will bail out in pthread_spinunlock()). 201 */ 202 if (thread->pt_next != NULL) { 203 PTHREADD_ADD(PTHREADD_SPINPREEMPT); 204 pthread__switch(thread, thread->pt_next); 205 } 206 /* try again */ 207 count = nspins; 208 SDPRINTF(("(pthread_spinlock %p) incrementing spinlock from %d\n", 209 thread, thread->pt_spinlocks)); 210 ++thread->pt_spinlocks; 211 } while (/*CONSTCOND*/1); 212 213 PTHREADD_ADD(PTHREADD_SPINLOCKS); 214 /* Got it! We're out of here. */ 215 } 216 217 218 int 219 pthread_spintrylock(pthread_t thread, pthread_spin_t *lock) 220 { 221 int ret; 222 223 SDPRINTF(("(pthread_spinlock %p) incrementing spinlock from %d\n", 224 thread, thread->pt_spinlocks)); 225 ++thread->pt_spinlocks; 226 227 ret = pthread__simple_lock_try(lock); 228 229 if (ret == 0) { 230 SDPRINTF(("(pthread_spintrylock %p) decrementing spinlock from %d\n", 231 thread, thread->pt_spinlocks)); 232 --thread->pt_spinlocks; 233 /* See above. */ 234 if (thread->pt_next != NULL) { 235 PTHREADD_ADD(PTHREADD_SPINPREEMPT); 236 pthread__switch(thread, thread->pt_next); 237 } 238 } 239 240 return ret; 241 } 242 243 244 void 245 pthread_spinunlock(pthread_t thread, pthread_spin_t *lock) 246 { 247 248 pthread__simple_unlock(lock); 249 SDPRINTF(("(pthread_spinunlock %p) decrementing spinlock %p (count %d)\n", 250 thread, lock, thread->pt_spinlocks)); 251 --thread->pt_spinlocks; 252 #ifdef PTHREAD_SPIN_DEBUG 253 pthread__assert(thread->pt_spinlocks >= 0); 254 #endif 255 PTHREADD_ADD(PTHREADD_SPINUNLOCKS); 256 257 /* 258 * If we were preempted while holding a spinlock, the 259 * scheduler will notice this and continue us. To be good 260 * citzens, we must now get out of here if that was our 261 * last spinlock. 262 * XXX when will we ever have more than one? 263 */ 264 265 if ((thread->pt_spinlocks == 0) && (thread->pt_next != NULL)) { 266 PTHREADD_ADD(PTHREADD_SPINPREEMPT); 267 pthread__switch(thread, thread->pt_next); 268 } 269 } 270 271 272 /* 273 * Public (POSIX-specified) spinlocks. 274 * These don't interact with the spin-preemption code, nor do they 275 * perform any adaptive sleeping. 276 */ 277 278 int 279 pthread_spin_init(pthread_spinlock_t *lock, int pshared) 280 { 281 282 #ifdef ERRORCHECK 283 if ((lock == NULL) || 284 ((pshared != PTHREAD_PROCESS_PRIVATE) && 285 (pshared != PTHREAD_PROCESS_SHARED))) 286 return EINVAL; 287 #endif 288 lock->pts_magic = _PT_SPINLOCK_MAGIC; 289 /* 290 * We don't actually use the pshared flag for anything; 291 * cpu simple locks have all the process-shared properties 292 * that we want anyway. 293 */ 294 lock->pts_flags = pshared; 295 pthread_lockinit(&lock->pts_spin); 296 297 return 0; 298 } 299 300 int 301 pthread_spin_destroy(pthread_spinlock_t *lock) 302 { 303 304 #ifdef ERRORCHECK 305 if ((lock == NULL) || (lock->pts_magic != _PT_SPINLOCK_MAGIC)) 306 return EINVAL; 307 308 if (lock->pts_spin != __SIMPLELOCK_UNLOCKED) 309 return EBUSY; 310 #endif 311 312 lock->pts_magic = _PT_SPINLOCK_DEAD; 313 314 return 0; 315 } 316 317 int 318 pthread_spin_lock(pthread_spinlock_t *lock) 319 { 320 321 #ifdef ERRORCHECK 322 if ((lock == NULL) || (lock->pts_magic != _PT_SPINLOCK_MAGIC)) 323 return EINVAL; 324 #endif 325 326 while (pthread__simple_lock_try(&lock->pts_spin) == 0) 327 /* spin */ ; 328 329 return 0; 330 } 331 332 int 333 pthread_spin_trylock(pthread_spinlock_t *lock) 334 { 335 336 #ifdef ERRORCHECK 337 if ((lock == NULL) || (lock->pts_magic != _PT_SPINLOCK_MAGIC)) 338 return EINVAL; 339 #endif 340 341 if (pthread__simple_lock_try(&lock->pts_spin) == 0) 342 return EBUSY; 343 344 return 0; 345 } 346 347 int 348 pthread_spin_unlock(pthread_spinlock_t *lock) 349 { 350 351 #ifdef ERRORCHECK 352 if ((lock == NULL) || (lock->pts_magic != _PT_SPINLOCK_MAGIC)) 353 return EINVAL; 354 #endif 355 356 pthread__simple_unlock(&lock->pts_spin); 357 358 return 0; 359 } 360
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