linuxthreads/mutex.c

   1 /* Linuxthreads - a simple clone()-based implementation of Posix        */
   2 /* threads for Linux.                                                   */
   3 /* Copyright (C) 1996 Xavier Leroy (Xavier.Leroy@inria.fr)              */
   4 /*                                                                      */
   5 /* This program is free software; you can redistribute it and/or        */
   6 /* modify it under the terms of the GNU Library General Public License  */
   7 /* as published by the Free Software Foundation; either version 2       */
   8 /* of the License, or (at your option) any later version.               */
   9 /*                                                                      */
  10 /* This program is distributed in the hope that it will be useful,      */
  11 /* but WITHOUT ANY WARRANTY; without even the implied warranty of       */
  12 /* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the        */
  13 /* GNU Library General Public License for more details.                 */
  14
  15 /* Mutexes */
  16
  17 #include <errno.h>
  18 #include <sched.h>
  19 #include <stddef.h>
  20 #include "pthread.h"
  21 #include "internals.h"
  22 #include "spinlock.h"
  23 #include "queue.h"
  24 #include "restart.h"
  25
  26 int __pthread_mutex_init(pthread_mutex_t * mutex,
  27                        const pthread_mutexattr_t * mutex_attr)
  28 {
  29   __pthread_init_lock(&mutex->m_lock);
  30   mutex->m_kind =
  31     mutex_attr == NULL ? PTHREAD_MUTEX_FAST_NP : mutex_attr->mutexkind;
  32   mutex->m_count = 0;
  33   mutex->m_owner = NULL;
  34   return 0;
  35 }
  36 weak_alias (__pthread_mutex_init, pthread_mutex_init)
  37
  38 int __pthread_mutex_destroy(pthread_mutex_t * mutex)
  39 {
  40   if (mutex->m_lock.status != 0) return EBUSY;
  41   return 0;
  42 }
  43 weak_alias (__pthread_mutex_destroy, pthread_mutex_destroy)
  44
  45 int __pthread_mutex_trylock(pthread_mutex_t * mutex)
  46 {
  47   pthread_descr self;
  48   int retcode;
  49
  50   switch(mutex->m_kind) {
  51   case PTHREAD_MUTEX_FAST_NP:
  52     retcode = __pthread_trylock(&mutex->m_lock);
  53     return retcode;
  54   case PTHREAD_MUTEX_RECURSIVE_NP:
  55     self = thread_self();
  56     if (mutex->m_owner == self) {
  57       mutex->m_count++;
  58       return 0;
  59     }
  60     retcode = __pthread_trylock(&mutex->m_lock);
  61     if (retcode == 0) {
  62       mutex->m_owner = self;
  63       mutex->m_count = 0;
  64     }
  65     return retcode;
  66   case PTHREAD_MUTEX_ERRORCHECK_NP:
  67     retcode = __pthread_trylock(&mutex->m_lock);
  68     if (retcode == 0) {
  69       mutex->m_owner = thread_self();
  70     }
  71     return retcode;
  72   default:
  73     return EINVAL;
  74   }
  75 }
  76 weak_alias (__pthread_mutex_trylock, pthread_mutex_trylock)
  77
  78 int __pthread_mutex_lock(pthread_mutex_t * mutex)
  79 {
  80   pthread_descr self;
  81
  82   switch(mutex->m_kind) {
  83   case PTHREAD_MUTEX_FAST_NP:
  84     __pthread_lock(&mutex->m_lock);
  85     return 0;
  86   case PTHREAD_MUTEX_RECURSIVE_NP:
  87     self = thread_self();
  88     if (mutex->m_owner == self) {
  89       mutex->m_count++;
  90       return 0;
  91     }
  92     __pthread_lock(&mutex->m_lock);
  93     mutex->m_owner = self;
  94     mutex->m_count = 0;
  95     return 0;
  96   case PTHREAD_MUTEX_ERRORCHECK_NP:
  97     self = thread_self();
  98     if (mutex->m_owner == self) return EDEADLK;
  99     __pthread_lock(&mutex->m_lock);
 100     mutex->m_owner = self;
 101     return 0;
 102   default:
 103     return EINVAL;
 104   }
 105 }
 106 weak_alias (__pthread_mutex_lock, pthread_mutex_lock)
 107
 108 int __pthread_mutex_unlock(pthread_mutex_t * mutex)
 109 {
 110   switch (mutex->m_kind) {
 111   case PTHREAD_MUTEX_FAST_NP:
 112     __pthread_unlock(&mutex->m_lock);
 113     return 0;
 114   case PTHREAD_MUTEX_RECURSIVE_NP:
 115     if (mutex->m_count > 0) {
 116       mutex->m_count--;
 117       return 0;
 118     }
 119     mutex->m_owner = NULL;
 120     __pthread_unlock(&mutex->m_lock);
 121     return 0;
 122   case PTHREAD_MUTEX_ERRORCHECK_NP:
 123     if (mutex->m_owner != thread_self() || mutex->m_lock.status == 0)
 124       return EPERM;
 125     mutex->m_owner = NULL;
 126     __pthread_unlock(&mutex->m_lock);
 127     return 0;
 128   default:
 129     return EINVAL;
 130   }
 131 }
 132 weak_alias (__pthread_mutex_unlock, pthread_mutex_unlock)
 133
 134 int __pthread_mutexattr_init(pthread_mutexattr_t *attr)
 135 {
 136   attr->mutexkind = PTHREAD_MUTEX_FAST_NP;
 137   return 0;
 138 }
 139 weak_alias (__pthread_mutexattr_init, pthread_mutexattr_init)
 140
 141 int __pthread_mutexattr_destroy(pthread_mutexattr_t *attr)
 142 {
 143   return 0;
 144 }
 145 weak_alias (__pthread_mutexattr_destroy, pthread_mutexattr_destroy)
 146
 147 int __pthread_mutexattr_settype(pthread_mutexattr_t *attr, int kind)
 148 {
 149   if (kind != PTHREAD_MUTEX_FAST_NP
 150       && kind != PTHREAD_MUTEX_RECURSIVE_NP
 151       && kind != PTHREAD_MUTEX_ERRORCHECK_NP)
 152     return EINVAL;
 153   attr->mutexkind = kind;
 154   return 0;
 155 }
 156 weak_alias (__pthread_mutexattr_settype, pthread_mutexattr_settype)
 157 strong_alias ( __pthread_mutexattr_settype, __pthread_mutexattr_setkind_np)
 158 weak_alias (__pthread_mutexattr_setkind_np, pthread_mutexattr_setkind_np)
 159
 160 int __pthread_mutexattr_gettype(const pthread_mutexattr_t *attr, int *kind)
 161 {
 162   *kind = attr->mutexkind;
 163   return 0;
 164 }
 165 weak_alias (__pthread_mutexattr_gettype, pthread_mutexattr_gettype)
 166 strong_alias (__pthread_mutexattr_gettype, __pthread_mutexattr_getkind_np)
 167 weak_alias (__pthread_mutexattr_getkind_np, pthread_mutexattr_getkind_np)
 168
 169 /* Once-only execution */
 170
 171 static pthread_mutex_t once_masterlock = PTHREAD_MUTEX_INITIALIZER;
 172 static pthread_cond_t once_finished = PTHREAD_COND_INITIALIZER;
 173
 174 enum { NEVER = 0, IN_PROGRESS = 1, DONE = 2 };
 175
 176 int __pthread_once(pthread_once_t * once_control, void (*init_routine)(void))
 177 {
 178   /* Test without locking first for speed */
 179   if (*once_control == DONE) return 0;
 180   /* Lock and test again */
 181   pthread_mutex_lock(&once_masterlock);
 182   /* If init_routine is being called from another routine, wait until
 183      it completes. */
 184   while (*once_control == IN_PROGRESS) {
 185     pthread_cond_wait(&once_finished, &once_masterlock);
 186   }
 187   /* Here *once_control is stable and either NEVER or DONE. */
 188   if (*once_control == NEVER) {
 189     *once_control = IN_PROGRESS;
 190     pthread_mutex_unlock(&once_masterlock);
 191     init_routine();
 192     pthread_mutex_lock(&once_masterlock);
 193     *once_control = DONE;
 194     pthread_cond_broadcast(&once_finished);
 195   }
 196   pthread_mutex_unlock(&once_masterlock);
 197   return 0;
 198 }
 199 weak_alias (__pthread_once, pthread_once)