pthread_lock.c revision 1.1.2.12
1 /* $NetBSD: pthread_lock.c,v 1.1.2.12 2002/11/14 04:10:08 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 <assert.h> 40 #include <errno.h> 41 #include <unistd.h> 42 43 #include "pthread.h" 44 #include "pthread_int.h" 45 46 #undef PTHREAD_SPIN_DEBUG 47 48 #ifdef PTHREAD_SPIN_DEBUG 49 #define SDPRINTF(x) DPRINTF(x) 50 #else 51 #define SDPRINTF(x) 52 #endif 53 54 /* How many times to try before checking whether we've been continued. */ 55 #define NSPINS 1 /* no point in actually spinning until MP works */ 56 57 static int nspins = NSPINS; 58 59 void 60 pthread_lockinit(pthread_spin_t *lock) 61 { 62 63 __cpu_simple_lock_init(lock); 64 } 65 66 void 67 pthread_spinlock(pthread_t thread, pthread_spin_t *lock) 68 { 69 int count, ret; 70 71 count = nspins; 72 SDPRINTF(("(pthread_spinlock %p) incrementing spinlock from %d\n", 73 thread, thread->pt_spinlocks)); 74 #ifdef PTHREAD_SPIN_DEBUG 75 if(!(thread->pt_spinlocks >= 0)) { 76 (void)kill(getpid(), SIGABRT); 77 _exit(1); 78 } 79 #endif 80 ++thread->pt_spinlocks; 81 82 do { 83 while (((ret = __cpu_simple_lock_try(lock)) == 0) && --count) 84 ; 85 86 if (ret == 1) 87 break; 88 89 SDPRINTF(("(pthread_spinlock %p) decrementing spinlock from %d\n", 90 thread, thread->pt_spinlocks)); 91 --thread->pt_spinlocks; 92 93 /* 94 * We may be preempted while spinning. If so, we will 95 * be restarted here if thread->pt_spinlocks is 96 * nonzero, which can happen if: 97 * a) we just got the lock 98 * b) we haven't yet decremented the lock count. 99 * If we're at this point, (b) applies. Therefore, 100 * check if we're being continued, and if so, bail. 101 * (in case (a), we should let the code finish and 102 * we will bail out in pthread_spinunlock()). 103 */ 104 if (thread->pt_next != NULL) { 105 PTHREADD_ADD(PTHREADD_SPINPREEMPT); 106 pthread__switch(thread, thread->pt_next); 107 } 108 /* try again */ 109 count = nspins; 110 SDPRINTF(("(pthread_spinlock %p) incrementing spinlock from %d\n", 111 thread, thread->pt_spinlocks)); 112 ++thread->pt_spinlocks; 113 } while (/*CONSTCOND*/1); 114 115 PTHREADD_ADD(PTHREADD_SPINLOCKS); 116 /* Got it! We're out of here. */ 117 } 118 119 120 int 121 pthread_spintrylock(pthread_t thread, pthread_spin_t *lock) 122 { 123 int ret; 124 125 SDPRINTF(("(pthread_spinlock %p) incrementing spinlock from %d\n", 126 thread, thread->pt_spinlocks)); 127 ++thread->pt_spinlocks; 128 129 ret = __cpu_simple_lock_try(lock); 130 131 if (ret == 0) { 132 SDPRINTF(("(pthread_spintrylock %p) decrementing spinlock from %d\n", 133 thread, thread->pt_spinlocks)); 134 --thread->pt_spinlocks; 135 /* See above. */ 136 if (thread->pt_next != NULL) { 137 PTHREADD_ADD(PTHREADD_SPINPREEMPT); 138 pthread__switch(thread, thread->pt_next); 139 } 140 } 141 142 return ret; 143 } 144 145 146 void 147 pthread_spinunlock(pthread_t thread, pthread_spin_t *lock) 148 { 149 150 __cpu_simple_unlock(lock); 151 SDPRINTF(("(pthread_spinunlock %p) decrementing spinlock from %d\n", 152 thread, thread->pt_spinlocks)); 153 --thread->pt_spinlocks; 154 #ifdef PTHREAD_SPIN_DEBUG 155 if (!(thread->pt_spinlocks >= 0)) { 156 (void)kill(getpid(), SIGABRT); 157 _exit(1); 158 } 159 #endif 160 PTHREADD_ADD(PTHREADD_SPINUNLOCKS); 161 162 /* 163 * If we were preempted while holding a spinlock, the 164 * scheduler will notice this and continue us. To be good 165 * citzens, we must now get out of here if that was our 166 * last spinlock. 167 * XXX when will we ever have more than one? 168 */ 169 170 if ((thread->pt_spinlocks == 0) && (thread->pt_next != NULL)) { 171 PTHREADD_ADD(PTHREADD_SPINPREEMPT); 172 pthread__switch(thread, thread->pt_next); 173 } 174 } 175 176 177 /* 178 * Public (POSIX-specified) spinlocks. 179 * These don't interact with the spin-preemption code, nor do they 180 * perform any adaptive sleeping. 181 */ 182 183 int 184 pthread_spin_init(pthread_spinlock_t *lock, int pshared) 185 { 186 187 #ifdef ERRORCHECK 188 if ((lock == NULL) || 189 ((pshared != PTHREAD_PROCESS_PRIVATE) && 190 (pshared != PTHREAD_PROCESS_SHARED))) 191 return EINVAL; 192 #endif 193 lock->pts_magic = _PT_SPINLOCK_MAGIC; 194 /* 195 * We don't actually use the pshared flag for anything; 196 * cpu simple locks have all the process-shared properties 197 * that we want anyway. 198 */ 199 lock->pts_flags = pshared; 200 pthread_lockinit(&lock->pts_spin); 201 202 return 0; 203 } 204 205 int 206 pthread_spin_destroy(pthread_spinlock_t *lock) 207 { 208 209 #ifdef ERRORCHECK 210 if ((lock == NULL) || (lock->pts_magic != _PT_SPINLOCK_MAGIC)) 211 return EINVAL; 212 213 if (lock->pts_spin != __SIMPLELOCK_UNLOCKED) 214 return EBUSY; 215 #endif 216 217 lock->pts_magic = _PT_SPINLOCK_DEAD; 218 219 return 0; 220 } 221 222 int 223 pthread_spin_lock(pthread_spinlock_t *lock) 224 { 225 226 #ifdef ERRORCHECK 227 if ((lock == NULL) || (lock->pts_magic != _PT_SPINLOCK_MAGIC)) 228 return EINVAL; 229 #endif 230 231 __cpu_simple_lock(&lock->pts_spin); 232 233 return 0; 234 } 235 236 int 237 pthread_spin_trylock(pthread_spinlock_t *lock) 238 { 239 240 #ifdef ERRORCHECK 241 if ((lock == NULL) || (lock->pts_magic != _PT_SPINLOCK_MAGIC)) 242 return EINVAL; 243 #endif 244 245 if (__cpu_simple_lock_try(&lock->pts_spin) == 0) 246 return EBUSY; 247 248 return 0; 249 } 250 251 int 252 pthread_spin_unlock(pthread_spinlock_t *lock) 253 { 254 255 #ifdef ERRORCHECK 256 if ((lock == NULL) || (lock->pts_magic != _PT_SPINLOCK_MAGIC)) 257 return EINVAL; 258 #endif 259 260 __cpu_simple_unlock(&lock->pts_spin); 261 262 return 0; 263 } 264
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