1 /* 2 * pte_mutex_check_need_init.c 3 * 4 * Description: 5 * This translation unit implements mutual exclusion (mutex) 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 44 #include "pthread.h" 45 #include "implement.h" 46 47 48 static struct pthread_mutexattr_t_ pte_recursive_mutexattr_s = 49 { 50 PTHREAD_PROCESS_PRIVATE, PTHREAD_MUTEX_RECURSIVE 51 }; 52 static struct pthread_mutexattr_t_ pte_errorcheck_mutexattr_s = 53 { 54 PTHREAD_PROCESS_PRIVATE, PTHREAD_MUTEX_ERRORCHECK 55 }; 56 static pthread_mutexattr_t pte_recursive_mutexattr = &pte_recursive_mutexattr_s; 57 static pthread_mutexattr_t pte_errorcheck_mutexattr = &pte_errorcheck_mutexattr_s; 58 59 60 int 61 pte_mutex_check_need_init (pthread_mutex_t * mutex) 62 { 63 register int result = 0; 64 register pthread_mutex_t mtx; 65 66 /* 67 * The following guarded test is specifically for statically 68 * initialised mutexes (via PTHREAD_MUTEX_INITIALIZER). 69 * 70 * Note that by not providing this synchronisation we risk 71 * introducing race conditions into applications which are 72 * correctly written. 73 * 74 * Approach 75 * -------- 76 * We know that static mutexes will not be PROCESS_SHARED 77 * so we can serialise access to internal state using 78 * critical sections rather than mutexes. 79 * 80 * If using a single global lock slows applications down too much, 81 * multiple global locks could be created and hashed on some random 82 * value associated with each mutex, the pointer perhaps. At a guess, 83 * a good value for the optimal number of global locks might be 84 * the number of processors + 1. 85 * 86 */ 87 88 89 pte_osMutexLock (pte_mutex_test_init_lock); 90 91 /* 92 * We got here possibly under race 93 * conditions. Check again inside the critical section 94 * and only initialise if the mutex is valid (not been destroyed). 95 * If a static mutex has been destroyed, the application can 96 * re-initialise it only by calling pthread_mutex_init() 97 * explicitly. 98 */ 99 mtx = *mutex; 100 101 if (mtx == PTHREAD_MUTEX_INITIALIZER) 102 { 103 result = pthread_mutex_init (mutex, NULL); 104 } 105 else if (mtx == PTHREAD_RECURSIVE_MUTEX_INITIALIZER) 106 { 107 result = pthread_mutex_init (mutex, &pte_recursive_mutexattr); 108 } 109 else if (mtx == PTHREAD_ERRORCHECK_MUTEX_INITIALIZER) 110 { 111 result = pthread_mutex_init (mutex, &pte_errorcheck_mutexattr); 112 } 113 else if (mtx == NULL) 114 { 115 /* 116 * The mutex has been destroyed while we were waiting to 117 * initialise it, so the operation that caused the 118 * auto-initialisation should fail. 119 */ 120 result = EINVAL; 121 } 122 123 pte_osMutexUnlock(pte_mutex_test_init_lock); 124 125 return (result); 126 } 127 128 129 130