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/*
* Copyright (c) 1998 John Birrell <jb@cimlogic.com.au>.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by John Birrell.
* 4. Neither the name of the author nor the names of any co-contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY JOHN BIRRELL AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
* $FreeBSD$
*
*/
/*
* POSIX stdio FILE locking functions. These assume that the locking
* is only required at FILE structure level, not at file descriptor
* level too.
*
*/
#include "namespace.h"
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <pthread.h>
#include "un-namespace.h"
/*
* Weak symbols for externally visible functions in this file:
*/
#pragma weak flockfile=_flockfile
#pragma weak _flockfile_debug=_flockfile_debug_stub
#pragma weak ftrylockfile=_ftrylockfile
#pragma weak funlockfile=_funlockfile
static int init_lock(FILE *);
/*
* The FILE lock structure. The FILE *fp is locked when the mutex
* is locked.
*/
struct __file_lock {
pthread_mutex_t fl_mutex;
pthread_t fl_owner; /* current owner */
int fl_count; /* recursive lock count */
};
/*
* We need to retain binary compatibility for a while. So pretend
* that _lock is part of FILE * even though it is dereferenced off
* _extra now. When we stop encoding the size of FILE into binaries
* this can be changed in stdio.h. This will reduce the amount of
* code that has to change in the future (just remove this comment
* and #define).
*/
#define _lock _extra->_mtlock
/*
* Allocate and initialize a file lock.
*/
static int
init_lock(FILE *fp)
{
struct __file_lock *p;
int ret;
if ((p = malloc(sizeof(struct __file_lock))) == NULL)
ret = -1;
else {
p->fl_mutex = PTHREAD_MUTEX_INITIALIZER;
p->fl_owner = NULL;
p->fl_count = 0;
fp->_lock = p;
ret = 0;
}
return (ret);
}
void
_flockfile(FILE *fp)
{
pthread_t curthread = _pthread_self();
/*
* Check if this is a real file with a valid lock, creating
* the lock if needed:
*/
if ((fp->_file >= 0) &&
((fp->_lock != NULL) || (init_lock(fp) == 0))) {
if (fp->_lock->fl_owner == curthread)
fp->_lock->fl_count++;
else {
/*
* Make sure this mutex is treated as a private
* internal mutex:
*/
_pthread_mutex_lock(&fp->_lock->fl_mutex);
fp->_lock->fl_owner = curthread;
fp->_lock->fl_count = 1;
}
}
}
/*
* This can be overriden by the threads library if it is linked in.
*/
void
_flockfile_debug_stub(FILE *fp, char *fname, int lineno)
{
_flockfile(fp);
}
int
_ftrylockfile(FILE *fp)
{
pthread_t curthread = _pthread_self();
int ret = 0;
/*
* Check if this is a real file with a valid lock, creating
* the lock if needed:
*/
if ((fp->_file >= 0) &&
((fp->_lock != NULL) || (init_lock(fp) == 0))) {
if (fp->_lock->fl_owner == curthread)
fp->_lock->fl_count++;
/*
* Make sure this mutex is treated as a private
* internal mutex:
*/
else if (_pthread_mutex_trylock(&fp->_lock->fl_mutex) == 0) {
fp->_lock->fl_owner = curthread;
fp->_lock->fl_count = 1;
}
else
ret = -1;
}
else
ret = -1;
return (ret);
}
void
_funlockfile(FILE *fp)
{
pthread_t curthread = _pthread_self();
/*
* Check if this is a real file with a valid lock owned
* by the current thread:
*/
if ((fp->_file >= 0) && (fp->_lock != NULL) &&
(fp->_lock->fl_owner == curthread)) {
/*
* Check if this thread has locked the FILE
* more than once:
*/
if (fp->_lock->fl_count > 1)
/*
* Decrement the count of the number of
* times the running thread has locked this
* file:
*/
fp->_lock->fl_count--;
else {
/*
* The running thread will release the
* lock now:
*/
fp->_lock->fl_count = 0;
fp->_lock->fl_owner = NULL;
_pthread_mutex_unlock(&fp->_lock->fl_mutex);
}
}
}
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