pthread_mutex.c revision 1.1.2.2
1 1.1.2.1 nathanw /* Copyright */ 2 1.1.2.1 nathanw 3 1.1.2.1 nathanw #include <assert.h> 4 1.1.2.1 nathanw #include <errno.h> 5 1.1.2.1 nathanw #include <signal.h> 6 1.1.2.1 nathanw #include <stdlib.h> 7 1.1.2.1 nathanw #include <ucontext.h> 8 1.1.2.1 nathanw #include <sys/queue.h> 9 1.1.2.1 nathanw 10 1.1.2.1 nathanw #include "pthread.h" 11 1.1.2.1 nathanw #include "pthread_int.h" 12 1.1.2.1 nathanw 13 1.1.2.1 nathanw 14 1.1.2.1 nathanw int 15 1.1.2.1 nathanw pthread_mutex_init(pthread_mutex_t *mutex, const pthread_mutexattr_t *attr) 16 1.1.2.1 nathanw { 17 1.1.2.1 nathanw 18 1.1.2.1 nathanw assert(mutex != NULL); 19 1.1.2.1 nathanw 20 1.1.2.1 nathanw /* XXX No mutex attr support yet. */ 21 1.1.2.1 nathanw if (attr != NULL) 22 1.1.2.1 nathanw return EINVAL; 23 1.1.2.1 nathanw 24 1.1.2.1 nathanw /* Allocate. */ 25 1.1.2.1 nathanw 26 1.1.2.2 nathanw mutex->ptm_magic = PT_MUTEX_MAGIC; 27 1.1.2.2 nathanw mutex->ptm_owner = NULL; 28 1.1.2.2 nathanw pthread_lockinit(&mutex->ptm_lock); 29 1.1.2.2 nathanw pthread_lockinit(&mutex->ptm_interlock); 30 1.1.2.2 nathanw PTQ_INIT(&mutex->ptm_blocked); 31 1.1.2.1 nathanw 32 1.1.2.1 nathanw return 0; 33 1.1.2.1 nathanw } 34 1.1.2.1 nathanw 35 1.1.2.1 nathanw 36 1.1.2.1 nathanw int 37 1.1.2.1 nathanw pthread_mutex_destroy(pthread_mutex_t *mutex) 38 1.1.2.1 nathanw { 39 1.1.2.1 nathanw 40 1.1.2.2 nathanw assert(mutex != NULL); 41 1.1.2.2 nathanw assert(mutex->ptm_lock == __SIMPLELOCK_UNLOCKED); 42 1.1.2.1 nathanw 43 1.1.2.2 nathanw mutex->ptm_magic = PT_MUTEX_DEAD; 44 1.1.2.1 nathanw 45 1.1.2.1 nathanw return 0; 46 1.1.2.1 nathanw } 47 1.1.2.1 nathanw 48 1.1.2.1 nathanw 49 1.1.2.2 nathanw /* 50 1.1.2.2 nathanw * Note regarding memory visibility: Pthreads has rules about memory 51 1.1.2.2 nathanw * visibility and mutexes. Very roughly: Memory a thread can see when 52 1.1.2.2 nathanw * it unlocks a mutex can be seen by another thread that locks the 53 1.1.2.2 nathanw * same mutex. 54 1.1.2.2 nathanw * 55 1.1.2.2 nathanw * A memory barrier after a lock and before an unlock will provide 56 1.1.2.2 nathanw * this behavior. This code relies on __cpu_simple_lock_try() to issue 57 1.1.2.2 nathanw * a barrier after obtaining a lock, and on __cpu_simple_unlock() to 58 1.1.2.2 nathanw * issue a barrier before releasing a lock. 59 1.1.2.2 nathanw */ 60 1.1.2.2 nathanw 61 1.1.2.1 nathanw int 62 1.1.2.1 nathanw pthread_mutex_lock(pthread_mutex_t *mutex) 63 1.1.2.1 nathanw { 64 1.1.2.1 nathanw pthread_t self; 65 1.1.2.2 nathanw #ifdef ERRORCHECK 66 1.1.2.2 nathanw if ((mutex == NULL) || (mutex->ptm_magic != PT_MUTEX_MAGIC)) 67 1.1.2.1 nathanw return EINVAL; 68 1.1.2.2 nathanw #endif 69 1.1.2.1 nathanw 70 1.1.2.2 nathanw while (/*CONSTCOND*/1) { 71 1.1.2.2 nathanw if (__cpu_simple_lock_try(&mutex->ptm_lock)) 72 1.1.2.2 nathanw break; /* got it! */ 73 1.1.2.1 nathanw 74 1.1.2.2 nathanw self = pthread__self(); 75 1.1.2.2 nathanw /* Okay, didn't look free. Get the interlock... */ 76 1.1.2.2 nathanw pthread_spinlock(self, &mutex->ptm_interlock); 77 1.1.2.2 nathanw /* The mutex_unlock routine will get the interlock 78 1.1.2.2 nathanw * before looking at the list of sleepers, so if the 79 1.1.2.2 nathanw * lock is held we can safely put ourselves on the 80 1.1.2.2 nathanw * sleep queue. If it's not held, we can try taking it 81 1.1.2.2 nathanw * again. 82 1.1.2.2 nathanw */ 83 1.1.2.2 nathanw if (mutex->ptm_lock == __SIMPLELOCK_LOCKED) { 84 1.1.2.2 nathanw PTQ_INSERT_TAIL(&mutex->ptm_blocked, self, pt_sleep); 85 1.1.2.2 nathanw self->pt_state = PT_STATE_BLOCKED; 86 1.1.2.2 nathanw pthread__block(self, &mutex->ptm_interlock); 87 1.1.2.2 nathanw /* interlock is not held when we return */ 88 1.1.2.2 nathanw } else { 89 1.1.2.2 nathanw pthread_spinunlock(self, &mutex->ptm_interlock); 90 1.1.2.2 nathanw } 91 1.1.2.2 nathanw /* Go around for another try. */ 92 1.1.2.1 nathanw } 93 1.1.2.1 nathanw 94 1.1.2.2 nathanw /* We have the lock! */ 95 1.1.2.2 nathanw #ifdef ERRORCHECK 96 1.1.2.2 nathanw mutex->ptm_owner = self; 97 1.1.2.2 nathanw #endif 98 1.1.2.1 nathanw return 0; 99 1.1.2.1 nathanw } 100 1.1.2.1 nathanw 101 1.1.2.1 nathanw 102 1.1.2.1 nathanw int 103 1.1.2.1 nathanw pthread_mutex_trylock(pthread_mutex_t *mutex) 104 1.1.2.1 nathanw { 105 1.1.2.1 nathanw 106 1.1.2.2 nathanw #ifdef ERRORCHECK 107 1.1.2.2 nathanw if ((mutex == NULL) || (mutex->ptm_magic != PT_MUTEX_MAGIC)) 108 1.1.2.1 nathanw return EINVAL; 109 1.1.2.2 nathanw #endif 110 1.1.2.1 nathanw 111 1.1.2.2 nathanw if (__cpu_simple_lock_try(&mutex->ptm_lock) == 0) 112 1.1.2.1 nathanw return EBUSY; 113 1.1.2.1 nathanw 114 1.1.2.2 nathanw #ifdef ERRORCHECK 115 1.1.2.2 nathanw mutex->ptm_owner = pthread__self(); 116 1.1.2.2 nathanw #endif 117 1.1.2.1 nathanw return 0; 118 1.1.2.1 nathanw } 119 1.1.2.1 nathanw 120 1.1.2.1 nathanw 121 1.1.2.1 nathanw int 122 1.1.2.1 nathanw pthread_mutex_unlock(pthread_mutex_t *mutex) 123 1.1.2.1 nathanw { 124 1.1.2.1 nathanw pthread_t self, blocked; 125 1.1.2.2 nathanw struct pt_queue_t blockedq, nullq = PTQ_HEAD_INITIALIZER; 126 1.1.2.1 nathanw 127 1.1.2.2 nathanw #ifdef ERRORCHECK 128 1.1.2.2 nathanw if ((mutex == NULL) || (mutex->ptm_magic != PT_MUTEX_MAGIC)) 129 1.1.2.1 nathanw return EINVAL; 130 1.1.2.1 nathanw 131 1.1.2.2 nathanw if (mutex->ptm_lock != __SIMPLELOCK_LOCKED) 132 1.1.2.1 nathanw return EPERM; /* Not exactly the right error. */ 133 1.1.2.1 nathanw 134 1.1.2.1 nathanw /* One is only permitted to unlock one's own mutexes. */ 135 1.1.2.2 nathanw if (mutex->ptm_owner != self) 136 1.1.2.1 nathanw return EPERM; 137 1.1.2.2 nathanw #endif 138 1.1.2.1 nathanw 139 1.1.2.2 nathanw self = pthread__self(); 140 1.1.2.2 nathanw pthread_spinlock(self, &mutex->ptm_interlock); 141 1.1.2.2 nathanw blockedq = mutex->ptm_blocked; 142 1.1.2.2 nathanw mutex->ptm_blocked = nullq; 143 1.1.2.2 nathanw #ifdef ERRORCHECK 144 1.1.2.2 nathanw mutex->ptm_owner = NULL; 145 1.1.2.2 nathanw #endif 146 1.1.2.2 nathanw __cpu_simple_unlock(&mutex->ptm_lock); 147 1.1.2.2 nathanw pthread_spinunlock(self, &mutex->ptm_interlock); 148 1.1.2.1 nathanw 149 1.1.2.2 nathanw /* Give everyone on the sleep queue another chance at the lock. */ 150 1.1.2.2 nathanw PTQ_FOREACH(blocked, &blockedq, pt_sleep) 151 1.1.2.1 nathanw pthread__sched(self, blocked); 152 1.1.2.1 nathanw 153 1.1.2.1 nathanw return 0; 154 1.1.2.1 nathanw } 155
Indexes created Mon Sep 22 21:09:42 GMT 2025