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  */
  31
  32 /*
  33  * POSIX stdio FILE locking functions. These assume that the locking
  34  * is only required at FILE structure level, not at file descriptor
  35  * level too.
  36  *
  37  */
  38
  39 #include "namespace.h"
  40 #include <stdio.h>
  41 #include <pthread.h>
  42 #include "un-namespace.h"
  43
  44 #include "local.h"
  45
  46 void
  47 _flockfile(FILE *fp)
  48 {
  49         pthread_t curthread = _pthread_self();
  50
  51         if (fp->_fl_owner == curthread)
  52                 fp->_fl_count++;
  53         else {
  54                 /*
  55                  * Make sure this mutex is treated as a private
  56                  * internal mutex:
  57                  */
  58                 _pthread_mutex_lock(&fp->_fl_mutex);
  59                 fp->_fl_owner = curthread;
  60                 fp->_fl_count = 1;
  61         }
  62 }
  63
  64 /*
  65  * This can be overriden by the threads library if it is linked in.
  66  */
  67 void
  68 _flockfile_debug_stub(FILE *fp, char *fname __unused, int lineno __unused)
  69 {
  70         _flockfile(fp);
  71 }
  72
  73 int
  74 _ftrylockfile(FILE *fp)
  75 {
  76         pthread_t curthread = _pthread_self();
  77         int     ret = 0;
  78
  79         if (fp->_fl_owner == curthread)
  80                 fp->_fl_count++;
  81         /*
  82          * Make sure this mutex is treated as a private
  83          * internal mutex:
  84          */
  85         else if (_pthread_mutex_trylock(&fp->_fl_mutex) == 0) {
  86                 fp->_fl_owner = curthread;
  87                 fp->_fl_count = 1;
  88         }
  89         else
  90                 ret = -1;
  91         return (ret);
  92 }
  93
  94 void
  95 _funlockfile(FILE *fp)
  96 {
  97         pthread_t       curthread = _pthread_self();
  98
  99         /*
 100          * Check if this file is owned by the current thread:
 101          */
 102         if (fp->_fl_owner == curthread) {
 103                 /*
 104                  * Check if this thread has locked the FILE
 105                  * more than once:
 106                  */
 107                 if (fp->_fl_count > 1) {
 108                         /*
 109                          * Decrement the count of the number of
 110                          * times the running thread has locked this
 111                          * file:
 112                          */
 113                         fp->_fl_count--;
 114                 } else {
 115                         /*
 116                          * The running thread will release the
 117                          * lock now:
 118                          */
 119                         fp->_fl_count = 0;
 120                         fp->_fl_owner = NULL;
 121                         _pthread_mutex_unlock(&fp->_fl_mutex);
 122                 }
 123         }
 124 }
 125
 126 /*
 127  * Weak symbols for externally visible functions in this file:
 128  */
 129 __weak_reference(_flockfile, flockfile);
 130 __weak_reference(_flockfile_debug_stub, _flockfile_debug);
 131 __weak_reference(_ftrylockfile, ftrylockfile);
 132 __weak_reference(_funlockfile, funlockfile);