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. 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  * $FreeBSD: src/lib/libc/stdio/_flock_stub.c,v 1.3 1999/08/28 00:00:55 peter Exp $
  33  * $DragonFly: src/lib/libc/stdio/_flock_stub.c,v 1.10 2005/07/23 23:14:44 joerg Exp $
  34  *
  35  */
  36
  37 #include "namespace.h"
  38 #include <stdio.h>
  39 #include <pthread.h>
  40 #include "un-namespace.h"
  41
  42 #include "local.h"
  43 #include "priv_stdio.h"
  44
  45 void __flockfile(FILE *fp);
  46 void __flockfile_debug(FILE *fp, char *fname, int lineno);
  47 int  __ftrylockfile(FILE *fp);
  48 void __funlockfile(FILE *fp);
  49
  50 /*
  51  * Externally visible weak symbols.
  52  */
  53 __weak_reference(__flockfile, flockfile);
  54 __weak_reference(__flockfile, _flockfile);
  55 __weak_reference(__flockfile_debug, _flockfile_debug);
  56 __weak_reference(__ftrylockfile, ftrylockfile);
  57 __weak_reference(__ftrylockfile, _ftrylockfile);
  58 __weak_reference(__funlockfile, funlockfile);
  59 __weak_reference(__funlockfile, _funlockfile);
  60
  61 void
  62 __flockfile(FILE *fp)
  63 {
  64         pthread_t curthread = _pthread_self();
  65
  66         if (fp->fl_owner == curthread)
  67                 fp->fl_count++;
  68         else {
  69                 /*
  70                  * Make sure this mutex is treated as a private
  71                  * internal mutex:
  72                  */
  73                 _pthread_mutex_lock(&fp->fl_mutex);
  74                 fp->fl_owner = curthread;
  75                 fp->fl_count = 1;
  76         }
  77 }
  78
  79 void
  80 __flockfile_debug(FILE *fp, char *fname __unused, int lineno __unused)
  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 }