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2 pj 1
 
1063 tullio 2
/*
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 * This program is free software; you can redistribute it and/or modify
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 * it under the terms of the GNU General Public License as published by
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 * the Free Software Foundation; either version 2 of the License, or
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 * (at your option) any later version.
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 *
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 * This program is distributed in the hope that it will be useful,
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 * but WITHOUT ANY WARRANTY; without even the implied warranty of
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 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
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 * GNU General Public License for more details.
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 *
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 * You should have received a copy of the GNU General Public License
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 * along with this program; if not, write to the Free Software
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 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
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 *
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 */
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2 pj 19
#include <fs/mutex.h>
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#include <fs/semaph.h>
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#include "mutex.h"
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#include "rwlock.h"
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void __rwlock_init(__rwlock_t *ptr)
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{
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  __mutex_init(&ptr->mutex,fsmutexattr);
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  __sem_init(&ptr->readers_semaph,0);
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  __sem_init(&ptr->writers_semaph,0);
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  ptr->active_readers=0;
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  ptr->active_writers=0;
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  ptr->blocked_readers=0;
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  ptr->blocked_writers=0;  
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}
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void __rwlock_rdlock(__rwlock_t *ptr)
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{
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  __mutex_lock(&ptr->mutex);
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  if (ptr->active_writers==0&&ptr->blocked_writers==0) {
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    ptr->active_readers++;
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    __sem_signal(&ptr->readers_semaph);
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  } else
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    ptr->blocked_readers++;
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  __mutex_unlock(&ptr->mutex);
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  __sem_wait(&ptr->readers_semaph);
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}
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int __rwlock_tryrdlock(__rwlock_t *ptr)
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{
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  int ret;
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  __mutex_lock(&ptr->mutex);
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  ret=0;
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  if (ptr->active_writers==0&&ptr->blocked_writers==0) {
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    ptr->active_readers++;
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    __sem_signal(&ptr->readers_semaph);
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  } else
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    ret=-1;
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  __mutex_unlock(&ptr->mutex);
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  if (ret==0) __sem_wait(&ptr->readers_semaph);
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  return ret;
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}
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void __rwlock_wrlock(__rwlock_t *ptr)
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{
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  __mutex_lock(&ptr->mutex);
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  if (ptr->active_readers==0&&ptr->active_writers==0) {
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    ptr->active_writers=1;
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    __sem_signal(&ptr->writers_semaph);
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  }
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  else
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    ptr->blocked_writers++;
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  __mutex_unlock(&ptr->mutex);
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  __sem_wait(&ptr->writers_semaph);
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}
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int __rwlock_trywrlock(__rwlock_t *ptr)
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{
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  int ret;
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  __mutex_lock(&ptr->mutex);
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  ret=0;
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  if (ptr->active_readers==0&&ptr->active_writers==0) {
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    ptr->active_writers=1;
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    __sem_signal(&ptr->writers_semaph);
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  }
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  else
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    ret=-1;
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  __mutex_unlock(&ptr->mutex);
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  if (ret==0) __sem_wait(&ptr->writers_semaph);
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  return ret;
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}
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void __rwlock_rdunlock(__rwlock_t *ptr)
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{
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  __mutex_lock(&ptr->mutex);
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  ptr->active_readers--;
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  if (ptr->active_readers==0&&ptr->blocked_writers>0) {
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    ptr->active_writers=1;
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    ptr->blocked_writers--;
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    __sem_signal(&ptr->writers_semaph);
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  }
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  __mutex_unlock(&ptr->mutex);
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}
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void __rwlock_wrunlock(__rwlock_t *ptr)
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{
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  __mutex_lock(&ptr->mutex);
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  ptr->active_writers=0;
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  if (ptr->blocked_readers>0) {
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    do {
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      ptr->blocked_readers--;
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      ptr->active_readers++;
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      __sem_signal(&ptr->readers_semaph);
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    } while(ptr->blocked_readers!=0);
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  } else if (ptr->blocked_writers>0) {
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    ptr->active_writers=1;
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    ptr->blocked_writers--;
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    __sem_signal(&ptr->writers_semaph);
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  }
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  __mutex_unlock(&ptr->mutex);
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}