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annotate src/atomic/SDL_spinlock.c @ 5222:9c0593fa27d6

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Create an OpenGL 1.1 context by default, if available. This is easier for people to set up and work with, and is more conformant to the way desktop OpenGL works.
author Sam Lantinga <slouken@libsdl.org>
date Mon, 07 Feb 2011 09:23:01 -0800
parents b938ad843e52
children 5d01d426f2ea
rev   line source
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1 /*
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2 SDL - Simple DirectMedia Layer
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3 Copyright (C) 1997-2010 Sam Lantinga
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4
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5 This library is free software; you can redistribute it and/or
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6 modify it under the terms of the GNU Lesser General Public
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7 License as published by the Free Software Foundation; either
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8 version 2.1 of the License, or (at your option) any later version.
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9
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10 This library is distributed in the hope that it will be useful,
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11 but WITHOUT ANY WARRANTY; without even the implied warranty of
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12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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13 Lesser General Public License for more details.
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14
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15 You should have received a copy of the GNU Lesser General Public
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16 License along with this library; if not, write to the Free Software
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17 Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
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18
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19 Sam Lantinga
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20 slouken@libsdl.org
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21 */
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22 #include "SDL_stdinc.h"
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23
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24 #include "SDL_atomic.h"
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25 #include "SDL_timer.h"
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26
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27 /* Don't do the check for Visual Studio 2005, it's safe here */
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28 #ifdef __WIN32__
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29 #include "../core/windows/SDL_windows.h"
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30 #endif
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31
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32 /* This function is where all the magic happens... */
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33 SDL_bool
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34 SDL_AtomicTryLock(SDL_SpinLock *lock)
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35 {
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36 #if defined(_MSC_VER)
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37 SDL_COMPILE_TIME_ASSERT(locksize, sizeof(*lock) == sizeof(long));
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38 return (InterlockedExchange((long*)lock, 1) == 0);
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39
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40 #elif defined(__MACOSX__)
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41 return OSAtomicCompareAndSwap32Barrier(0, 1, lock);
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42
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43 #elif HAVE_GCC_ATOMICS || HAVE_GCC_SYNC_LOCK_TEST_AND_SET
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44 return (__sync_lock_test_and_set(lock, 1) == 0);
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45
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46 #elif defined(__GNUC__) && defined(__arm__) && defined(__ARM_ARCH_5__)
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47 int result;
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48 __asm__ __volatile__ (
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49 "swp %0, %1, [%2]\n"
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50 : "=&r,&r" (result) : "r,0" (1), "r,r" (lock) : "memory");
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51 return (result == 0);
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52
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53 #elif defined(__GNUC__) && defined(__arm__)
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54 int result;
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55 __asm__ __volatile__ (
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56 "ldrex %0, [%2]\nteq %0, #0\nstrexeq %0, %1, [%2]"
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57 : "=&r" (result) : "r" (1), "r" (lock) : "cc", "memory");
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58 return (result == 0);
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59
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60 #else
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61 /* Need CPU instructions for spinlock here! */
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62 __need_spinlock_implementation__
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63 #endif
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64 }
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65
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66 void
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67 SDL_AtomicLock(SDL_SpinLock *lock)
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68 {
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69 /* FIXME: Should we have an eventual timeout? */
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70 while (!SDL_AtomicTryLock(lock)) {
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71 SDL_Delay(0);
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72 }
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73 }
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74
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75 void
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76 SDL_AtomicUnlock(SDL_SpinLock *lock)
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77 {
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78 #if defined(_MSC_VER)
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79 _ReadWriteBarrier();
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80 *lock = 0;
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81
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82 #elif HAVE_GCC_ATOMICS || HAVE_GCC_SYNC_LOCK_TEST_AND_SET
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83 __sync_lock_release(lock);
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84
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85 #else
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86 *lock = 0;
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87 #endif
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88 }
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89
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90 /* vi: set ts=4 sw=4 expandtab: */