1/*
2 * pthread_rwlock_destroy.c
3 *
4 * Description:
5 * This translation unit implements read/write lock primitives.
6 *
7 * --------------------------------------------------------------------------
8 *
9 *      Pthreads-win32 - POSIX Threads Library for Win32
10 *      Copyright(C) 1998 John E. Bossom
11 *      Copyright(C) 1999,2005 Pthreads-win32 contributors
12 *
13 *      Contact Email: rpj@callisto.canberra.edu.au
14 *
15 *      The current list of contributors is contained
16 *      in the file CONTRIBUTORS included with the source
17 *      code distribution. The list can also be seen at the
18 *      following World Wide Web location:
19 *      http://sources.redhat.com/pthreads-win32/contributors.html
20 *
21 *      This library is free software; you can redistribute it and/or
22 *      modify it under the terms of the GNU Lesser General Public
23 *      License as published by the Free Software Foundation; either
24 *      version 2 of the License, or (at your option) any later version.
25 *
26 *      This library is distributed in the hope that it will be useful,
27 *      but WITHOUT ANY WARRANTY; without even the implied warranty of
28 *      MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
29 *      Lesser General Public License for more details.
30 *
31 *      You should have received a copy of the GNU Lesser General Public
32 *      License along with this library in the file COPYING.LIB;
33 *      if not, write to the Free Software Foundation, Inc.,
34 *      59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
35 */
36
37#include <limits.h>
38
39#include "pthread.h"
40#include "implement.h"
41
42int
43pthread_rwlock_destroy (pthread_rwlock_t * rwlock)
44{
45  pthread_rwlock_t rwl;
46  int result = 0, result1 = 0, result2 = 0;
47
48  if (rwlock == NULL || *rwlock == NULL)
49    {
50      return EINVAL;
51    }
52
53  if (*rwlock != PTHREAD_RWLOCK_INITIALIZER)
54    {
55      rwl = *rwlock;
56
57      if (rwl->nMagic != PTW32_RWLOCK_MAGIC)
58	{
59	  return EINVAL;
60	}
61
62      if ((result = pthread_mutex_lock (&(rwl->mtxExclusiveAccess))) != 0)
63	{
64	  return result;
65	}
66
67      if ((result =
68	   pthread_mutex_lock (&(rwl->mtxSharedAccessCompleted))) != 0)
69	{
70	  (void) pthread_mutex_unlock (&(rwl->mtxExclusiveAccess));
71	  return result;
72	}
73
74      /*
75       * Check whether any threads own/wait for the lock (wait for ex.access);
76       * report "BUSY" if so.
77       */
78      if (rwl->nExclusiveAccessCount > 0
79	  || rwl->nSharedAccessCount > rwl->nCompletedSharedAccessCount)
80	{
81	  result = pthread_mutex_unlock (&(rwl->mtxSharedAccessCompleted));
82	  result1 = pthread_mutex_unlock (&(rwl->mtxExclusiveAccess));
83	  result2 = EBUSY;
84	}
85      else
86	{
87	  rwl->nMagic = 0;
88
89	  if ((result =
90	       pthread_mutex_unlock (&(rwl->mtxSharedAccessCompleted))) != 0)
91	    {
92	      pthread_mutex_unlock (&rwl->mtxExclusiveAccess);
93	      return result;
94	    }
95
96	  if ((result =
97	       pthread_mutex_unlock (&(rwl->mtxExclusiveAccess))) != 0)
98	    {
99	      return result;
100	    }
101
102	  *rwlock = NULL;	/* Invalidate rwlock before anything else */
103	  result = pthread_cond_destroy (&(rwl->cndSharedAccessCompleted));
104	  result1 = pthread_mutex_destroy (&(rwl->mtxSharedAccessCompleted));
105	  result2 = pthread_mutex_destroy (&(rwl->mtxExclusiveAccess));
106	  (void) free (rwl);
107	}
108    }
109  else
110    {
111      ptw32_mcs_local_node_t node;
112      /*
113       * See notes in ptw32_rwlock_check_need_init() above also.
114       */
115      ptw32_mcs_lock_acquire(&ptw32_rwlock_test_init_lock, &node);
116
117      /*
118       * Check again.
119       */
120      if (*rwlock == PTHREAD_RWLOCK_INITIALIZER)
121	{
122	  /*
123	   * This is all we need to do to destroy a statically
124	   * initialised rwlock that has not yet been used (initialised).
125	   * If we get to here, another thread
126	   * waiting to initialise this rwlock will get an EINVAL.
127	   */
128	  *rwlock = NULL;
129	}
130      else
131	{
132	  /*
133	   * The rwlock has been initialised while we were waiting
134	   * so assume it's in use.
135	   */
136	  result = EBUSY;
137	}
138
139      ptw32_mcs_lock_release(&node);
140    }
141
142  return ((result != 0) ? result : ((result1 != 0) ? result1 : result2));
143}
144