lib/libc/stdio/_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  * $FreeBSD: src/lib/libc/stdio/_flock_stub.c,v 1.16 2008/04/17 22:17:53 jhb Exp $
  30  * $DragonFly: src/lib/libc/stdio/_flock_stub.c,v 1.10 2005/07/23 23:14:44 joerg Exp $
  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 "namespace.h"
  41 #include <stdio.h>
  42 #include <pthread.h>
  43 #include "un-namespace.h"
  44
  45 #include "local.h"
  46 #include "priv_stdio.h"
  47
  48
  49 /*
  50  * Weak symbols for externally visible functions in this file:
  51  */
  52 __weak_reference(_flockfile, flockfile);
  53 __weak_reference(_flockfile_debug_stub, _flockfile_debug);
  54 __weak_reference(_ftrylockfile, ftrylockfile);
  55 __weak_reference(_funlockfile, funlockfile);
  56
  57 void
  58 _flockfile(FILE *fp)
  59 {
  60         pthread_t curthread = _pthread_self();
  61
  62         if (fp->_fl_owner == curthread)
  63                 fp->_fl_count++;
  64         else {
  65                 /*
  66                  * Make sure this mutex is treated as a private
  67                  * internal mutex:
  68                  */
  69                 _pthread_mutex_lock(&fp->_fl_mutex);
  70                 fp->_fl_owner = curthread;
  71                 fp->_fl_count = 1;
  72         }
  73 }
  74
  75 /*
  76  * This can be overriden by the threads library if it is linked in.
  77  */
  78 void
  79 _flockfile_debug_stub(FILE *fp, char *fname __unused, int lineno __unused)
  80 {
  81         _flockfile(fp);
  82 }
  83
  84 int
  85 _ftrylockfile(FILE *fp)
  86 {
  87         pthread_t curthread = _pthread_self();
  88         int     ret = 0;
  89
  90         if (fp->_fl_owner == curthread)
  91                 fp->_fl_count++;
  92         /*
  93          * Make sure this mutex is treated as a private
  94          * internal mutex:
  95          */
  96         else if (_pthread_mutex_trylock(&fp->_fl_mutex) == 0) {
  97                 fp->_fl_owner = curthread;
  98                 fp->_fl_count = 1;
  99         }
 100         else
 101                 ret = -1;
 102         return (ret);
 103 }
 104
 105 void
 106 _funlockfile(FILE *fp)
 107 {
 108         pthread_t       curthread = _pthread_self();
 109
 110         /*
 111          * Check if this file is owned by the current thread:
 112          */
 113         if (fp->_fl_owner == curthread) {
 114                 /*
 115                  * Check if this thread has locked the FILE
 116                  * more than once:
 117                  */
 118                 if (fp->_fl_count > 1) {
 119                         /*
 120                          * Decrement the count of the number of
 121                          * times the running thread has locked this
 122                          * file:
 123                          */
 124                         fp->_fl_count--;
 125                 } else {
 126                         /*
 127                          * The running thread will release the
 128                          * lock now:
 129                          */
 130                         fp->_fl_count = 0;
 131                         fp->_fl_owner = NULL;
 132                         _pthread_mutex_unlock(&fp->_fl_mutex);
 133                 }
 134         }
 135 }