1 /* 2 * pthread_mutex_trylock.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 #include "pthread.h" 44 #include "implement.h" 45 46 47 int 48 pthread_mutex_trylock (pthread_mutex_t * mutex) 49 { 50 int result = 0; 51 pthread_mutex_t mx; 52 53 /* 54 * Let the system deal with invalid pointers. 55 */ 56 57 /* 58 * We do a quick check to see if we need to do more work 59 * to initialise a static mutex. We check 60 * again inside the guarded section of pte_mutex_check_need_init() 61 * to avoid race conditions. 62 */ 63 if (*mutex >= PTHREAD_ERRORCHECK_MUTEX_INITIALIZER) 64 { 65 if ((result = pte_mutex_check_need_init (mutex)) != 0) 66 { 67 return (result); 68 } 69 } 70 71 mx = *mutex; 72 73 if (0 == PTE_ATOMIC_COMPARE_EXCHANGE (&mx->lock_idx,1,0)) 74 { 75 if (mx->kind != PTHREAD_MUTEX_NORMAL) 76 { 77 mx->recursive_count = 1; 78 mx->ownerThread = pthread_self (); 79 } 80 } 81 else 82 { 83 if (mx->kind == PTHREAD_MUTEX_RECURSIVE && 84 pthread_equal (mx->ownerThread, pthread_self ())) 85 { 86 mx->recursive_count++; 87 } 88 else 89 { 90 result = EBUSY; 91 } 92 } 93 94 return (result); 95 } 96