stdio/FreeBSD/_flock_stub.c

   1 /*
   2  * Copyright (c) 1998 John Birrell <jb@cimlogic.com.au>.
   3  * All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  * 1. Redistributions of source code must retain the above copyright
   9  *    notice, this list of conditions and the following disclaimer.
  10  * 2. Redistributions in binary form must reproduce the above copyright
  11  *    notice, this list of conditions and the following disclaimer in the
  12  *    documentation and/or other materials provided with the distribution.
  13  * 3. All advertising materials mentioning features or use of this software
  14  *    must display the following acknowledgement:
  15  *      This product includes software developed by John Birrell.
  16  * 4. Neither the name of the author nor the names of any co-contributors
  17  *    may be used to endorse or promote products derived from this software
  18  *    without specific prior written permission.
  19  *
  20  * THIS SOFTWARE IS PROVIDED BY JOHN BIRRELL AND CONTRIBUTORS ``AS IS'' AND
  21  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  22  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  23  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  24  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  25  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  26  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  27  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  28  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  29  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  30  * SUCH DAMAGE.
  31  */
  32
  33 /*
  34  * POSIX stdio FILE locking functions. These assume that the locking
  35  * is only required at FILE structure level, not at file descriptor
  36  * level too.
  37  *
  38  */
  39
  40 #include <sys/cdefs.h>
  41 __FBSDID("$FreeBSD: src/lib/libc/stdio/_flock_stub.c,v 1.14 2004/03/09 04:51:58 jb Exp $");
  42
  43 #include "namespace.h"
  44 #include <stdio.h>
  45 #include <stdlib.h>
  46 #include <string.h>
  47 #include <pthread.h>
  48 #include "un-namespace.h"
  49
  50 #include "local.h"
  51
  52
  53 /*
  54  * Weak symbols for externally visible functions in this file:
  55  */
  56 __weak_reference(_flockfile, flockfile);
  57 __weak_reference(_flockfile_debug_stub, _flockfile_debug);
  58 __weak_reference(_ftrylockfile, ftrylockfile);
  59 __weak_reference(_funlockfile, funlockfile);
  60
  61 /*
  62  * We need to retain binary compatibility for a while.  So pretend
  63  * that _lock is part of FILE * even though it is dereferenced off
  64  * _extra now.  When we stop encoding the size of FILE into binaries
  65  * this can be changed in stdio.h.  This will reduce the amount of
  66  * code that has to change in the future (just remove this comment
  67  * and #define).
  68  */
  69 #define _lock _extra
  70
  71 void
  72 _flockfile(FILE *fp)
  73 {
  74         pthread_t curthread = _pthread_self();
  75
  76         if (fp->_lock->fl_owner == curthread)
  77                 fp->_lock->fl_count++;
  78         else {
  79                 /*
  80                  * Make sure this mutex is treated as a private
  81                  * internal mutex:
  82                  */
  83                 _pthread_mutex_lock(&fp->_lock->fl_mutex);
  84                 fp->_lock->fl_owner = curthread;
  85                 fp->_lock->fl_count = 1;
  86         }
  87 }
  88
  89 /*
  90  * This can be overriden by the threads library if it is linked in.
  91  */
  92 void
  93 _flockfile_debug_stub(FILE *fp, char *fname, int lineno)
  94 {
  95         _flockfile(fp);
  96 }
  97
  98 int
  99 _ftrylockfile(FILE *fp)
 100 {
 101         pthread_t curthread = _pthread_self();
 102         int     ret = 0;
 103
 104         if (fp->_lock->fl_owner == curthread)
 105                 fp->_lock->fl_count++;
 106         /*
 107          * Make sure this mutex is treated as a private
 108          * internal mutex:
 109          */
 110         else if (_pthread_mutex_trylock(&fp->_lock->fl_mutex) == 0) {
 111                 fp->_lock->fl_owner = curthread;
 112                 fp->_lock->fl_count = 1;
 113         }
 114         else
 115                 ret = -1;
 116         return (ret);
 117 }
 118
 119 void
 120 _funlockfile(FILE *fp)
 121 {
 122         pthread_t       curthread = _pthread_self();
 123
 124         /*
 125          * Check if this file is owned by the current thread:
 126          */
 127         if (fp->_lock->fl_owner == curthread) {
 128                 /*
 129                  * Check if this thread has locked the FILE
 130                  * more than once:
 131                  */
 132                 if (fp->_lock->fl_count > 1)
 133                         /*
 134                          * Decrement the count of the number of
 135                          * times the running thread has locked this
 136                          * file:
 137                          */
 138                         fp->_lock->fl_count--;
 139                 else {
 140                         /*
 141                          * The running thread will release the
 142                          * lock now:
 143                          */
 144                         fp->_lock->fl_count = 0;
 145                         fp->_lock->fl_owner = NULL;
 146                         _pthread_mutex_unlock(&fp->_lock->fl_mutex);
 147                 }
 148         }
 149 }