1 /* 2 * pthread_rwlock_destroy.c 3 * 4 * Description: 5 * This translation unit implements read/write lock primitives. 6 * 7 * -------------------------------------------------------------------------- 8 * 9 * Pthreads-embedded (PTE) - POSIX Threads Library for embedded systems 10 * Copyright(C) 2008 Jason Schmidlapp 11 * 12 * Contact Email: jschmidlapp@users.sourceforge.net 13 * 14 * 15 * Based upon Pthreads-win32 - POSIX Threads Library for Win32 16 * Copyright(C) 1998 John E. Bossom 17 * Copyright(C) 1999,2005 Pthreads-win32 contributors 18 * 19 * Contact Email: rpj@callisto.canberra.edu.au 20 * 21 * The original list of contributors to the Pthreads-win32 project 22 * is contained in the file CONTRIBUTORS.ptw32 included with the 23 * source code distribution. The list can also be seen at the 24 * following World Wide Web location: 25 * http://sources.redhat.com/pthreads-win32/contributors.html 26 * 27 * This library is free software; you can redistribute it and/or 28 * modify it under the terms of the GNU Lesser General Public 29 * License as published by the Free Software Foundation; either 30 * version 2 of the License, or (at your option) any later version. 31 * 32 * This library is distributed in the hope that it will be useful, 33 * but WITHOUT ANY WARRANTY; without even the implied warranty of 34 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 35 * Lesser General Public License for more details. 36 * 37 * You should have received a copy of the GNU Lesser General Public 38 * License along with this library in the file COPYING.LIB; 39 * if not, write to the Free Software Foundation, Inc., 40 * 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA 41 */ 42 43 #include <stdlib.h> 44 #include <errno.h> 45 #include <limits.h> 46 47 #include "pthread.h" 48 #include "implement.h" 49 50 int 51 pthread_rwlock_destroy (pthread_rwlock_t * rwlock) 52 { 53 pthread_rwlock_t rwl; 54 int result = 0, result1 = 0, result2 = 0; 55 56 if (rwlock == NULL || *rwlock == NULL) 57 { 58 return EINVAL; 59 } 60 61 if (*rwlock != PTHREAD_RWLOCK_INITIALIZER) 62 { 63 rwl = *rwlock; 64 65 if (rwl->nMagic != PTE_RWLOCK_MAGIC) 66 { 67 return EINVAL; 68 } 69 70 if ((result = pthread_mutex_lock (&(rwl->mtxExclusiveAccess))) != 0) 71 { 72 return result; 73 } 74 75 if ((result = 76 pthread_mutex_lock (&(rwl->mtxSharedAccessCompleted))) != 0) 77 { 78 (void) pthread_mutex_unlock (&(rwl->mtxExclusiveAccess)); 79 return result; 80 } 81 82 /* 83 * Check whether any threads own/wait for the lock (wait for ex.access); 84 * report "BUSY" if so. 85 */ 86 if (rwl->nExclusiveAccessCount > 0 87 || rwl->nSharedAccessCount > rwl->nCompletedSharedAccessCount) 88 { 89 result = pthread_mutex_unlock (&(rwl->mtxSharedAccessCompleted)); 90 result1 = pthread_mutex_unlock (&(rwl->mtxExclusiveAccess)); 91 result2 = EBUSY; 92 } 93 else 94 { 95 rwl->nMagic = 0; 96 97 if ((result = 98 pthread_mutex_unlock (&(rwl->mtxSharedAccessCompleted))) != 0) 99 { 100 pthread_mutex_unlock (&rwl->mtxExclusiveAccess); 101 return result; 102 } 103 104 if ((result = 105 pthread_mutex_unlock (&(rwl->mtxExclusiveAccess))) != 0) 106 { 107 return result; 108 } 109 110 *rwlock = NULL; /* Invalidate rwlock before anything else */ 111 result = pthread_cond_destroy (&(rwl->cndSharedAccessCompleted)); 112 result1 = pthread_mutex_destroy (&(rwl->mtxSharedAccessCompleted)); 113 result2 = pthread_mutex_destroy (&(rwl->mtxExclusiveAccess)); 114 (void) free (rwl); 115 } 116 } 117 else 118 { 119 /* 120 * See notes in pte_rwlock_check_need_init() above also. 121 */ 122 123 pte_osMutexLock (pte_rwlock_test_init_lock); 124 125 /* 126 * Check again. 127 */ 128 if (*rwlock == PTHREAD_RWLOCK_INITIALIZER) 129 { 130 /* 131 * This is all we need to do to destroy a statically 132 * initialised rwlock that has not yet been used (initialised). 133 * If we get to here, another thread 134 * waiting to initialise this rwlock will get an EINVAL. 135 */ 136 *rwlock = NULL; 137 } 138 else 139 { 140 /* 141 * The rwlock has been initialised while we were waiting 142 * so assume it's in use. 143 */ 144 result = EBUSY; 145 } 146 147 pte_osMutexUnlock(pte_rwlock_test_init_lock); 148 149 } 150 151 return ((result != 0) ? result : ((result1 != 0) ? result1 : result2)); 152 } 153