1 /* 2 * pthread_spin_trylock.c 3 * 4 * Description: 5 * This translation unit implements spin 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 44 #include "pthread.h" 45 #include "implement.h" 46 47 48 int 49 pthread_spin_trylock (pthread_spinlock_t * lock) 50 { 51 register pthread_spinlock_t s; 52 53 if (NULL == lock || NULL == *lock) 54 { 55 return (EINVAL); 56 } 57 58 if (*lock == PTHREAD_SPINLOCK_INITIALIZER) 59 { 60 int result; 61 62 if ((result = pte_spinlock_check_need_init (lock)) != 0) 63 { 64 return (result); 65 } 66 } 67 68 s = *lock; 69 70 switch ((long) 71 PTE_ATOMIC_COMPARE_EXCHANGE (&(s->interlock), 72 PTE_SPIN_LOCKED, 73 PTE_SPIN_UNLOCKED)) 74 { 75 case PTE_SPIN_UNLOCKED: 76 return 0; 77 case PTE_SPIN_LOCKED: 78 return EBUSY; 79 case PTE_SPIN_USE_MUTEX: 80 return pthread_mutex_trylock (&(s->u.mutex)); 81 } 82 83 return EINVAL; 84 } 85