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. Neither the name of the author nor the names of any co-contributors
  14  *    may be used to endorse or promote products derived from this software
  15  *    without specific prior written permission.
  16  *
  17  * THIS SOFTWARE IS PROVIDED BY JOHN BIRRELL AND CONTRIBUTORS ``AS IS'' AND
  18  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  19  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  20  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  21  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  22  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  23  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  24  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  25  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  26  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  27  * SUCH DAMAGE.
  28  */
  29
  30 /*
  31  * POSIX stdio FILE locking functions. These assume that the locking
  32  * is only required at FILE structure level, not at file descriptor
  33  * level too.
  34  *
  35  */
  36
  37 #include <sys/cdefs.h>
  38 __FBSDID("$FreeBSD: src/lib/libc/stdio/_flock_stub.c,v 1.16 2008/04/17 22:17:53 jhb Exp $");
  39
  40 #include "namespace.h"
  41 #include <stdio.h>
  42 #include <stdlib.h>
  43 #include <string.h>
  44 #include <pthread.h>
  45 #include "un-namespace.h"
  46
  47 #include "local.h"
  48
  49
  50 /*
  51  * Weak symbols for externally visible functions in this file:
  52  */
  53 __weak_reference(_flockfile, flockfile);
  54 __weak_reference(_flockfile_debug_stub, _flockfile_debug);
  55 __weak_reference(_ftrylockfile, ftrylockfile);
  56 __weak_reference(_funlockfile, funlockfile);
  57
  58 void
  59 _flockfile(FILE *fp)
  60 {
  61         pthread_t curthread = _pthread_self();
  62
  63         if (fp->_fl_owner == curthread)
  64                 fp->_fl_count++;
  65         else {
  66                 /*
  67                  * Make sure this mutex is treated as a private
  68                  * internal mutex:
  69                  */
  70                 _pthread_mutex_lock(&fp->_fl_mutex);
  71                 fp->_fl_owner = curthread;
  72                 fp->_fl_count = 1;
  73         }
  74 }
  75
  76 /*
  77  * This can be overriden by the threads library if it is linked in.
  78  */
  79 void
  80 _flockfile_debug_stub(FILE *fp, char *fname, int lineno)
  81 {
  82         _flockfile(fp);
  83 }
  84
  85 int
  86 _ftrylockfile(FILE *fp)
  87 {
  88         pthread_t curthread = _pthread_self();
  89         int     ret = 0;
  90
  91         if (fp->_fl_owner == curthread)
  92                 fp->_fl_count++;
  93         /*
  94          * Make sure this mutex is treated as a private
  95          * internal mutex:
  96          */
  97         else if (_pthread_mutex_trylock(&fp->_fl_mutex) == 0) {
  98                 fp->_fl_owner = curthread;
  99                 fp->_fl_count = 1;
 100         }
 101         else
 102                 ret = -1;
 103         return (ret);
 104 }
 105
 106 void
 107 _funlockfile(FILE *fp)
 108 {
 109         pthread_t       curthread = _pthread_self();
 110
 111         /*
 112          * Check if this file is owned by the current thread:
 113          */
 114         if (fp->_fl_owner == curthread) {
 115                 /*
 116                  * Check if this thread has locked the FILE
 117                  * more than once:
 118                  */
 119                 if (fp->_fl_count > 1)
 120                         /*
 121                          * Decrement the count of the number of
 122                          * times the running thread has locked this
 123                          * file:
 124                          */
 125                         fp->_fl_count--;
 126                 else {
 127                         /*
 128                          * The running thread will release the
 129                          * lock now:
 130                          */
 131                         fp->_fl_count = 0;
 132                         fp->_fl_owner = NULL;
 133                         _pthread_mutex_unlock(&fp->_fl_mutex);
 134                 }
 135         }
 136 }