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annotate src/atomic/SDL_spinlock.c @ 5028:fffb33ae85e8

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Whoops, good catch from Greg Jandl
author Sam Lantinga <slouken@libsdl.org>
date Tue, 18 Jan 2011 22:10:37 -0800
parents 1bf9e38431ec
children fd125217f00c
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
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28 /* This function is where all the magic happens... */
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29 SDL_bool
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30 SDL_AtomicTryLock(SDL_SpinLock *lock)
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31 {
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32 #if defined(_MSC_VER)
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33 SDL_COMPILE_TIME_ASSERT(locksize, sizeof(*lock) == sizeof(long));
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34 return (_InterlockedExchange((long*)lock, 1) == 0);
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35
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36 #elif defined(__MACOSX__)
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37 return OSAtomicCompareAndSwap32Barrier(0, 1, lock);
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38
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39 #elif defined(HAVE_GCC_ATOMICS)
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40 return (__sync_lock_test_and_set(lock, 1) == 0);
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41
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42 #elif defined(__GNUC__) && defined(__arm__) && defined(__ARM_ARCH_5__)
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43 int result;
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44 __asm__ __volatile__ (
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45 "swp %0, %1, [%2]\n"
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46 : "=&r,&r" (result) : "r,0" (1), "r,r" (lock) : "memory");
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47 return (result == 0);
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48
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49 #elif defined(__GNUC__) && defined(__arm__)
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50 int result;
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51 __asm__ __volatile__ (
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52 "ldrex %0, [%2]\nteq %0, #0\nstrexeq %0, %1, [%2]"
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53 : "=&r" (result) : "r" (1), "r" (lock) : "cc", "memory");
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54 return (result == 0);
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55
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56 #else
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57 /* Need CPU instructions for spinlock here! */
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58 __need_spinlock_implementation__
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59 #endif
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60 }
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61
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62 void
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63 SDL_AtomicLock(SDL_SpinLock *lock)
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64 {
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65 /* FIXME: Should we have an eventual timeout? */
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66 while (!SDL_AtomicTryLock(lock)) {
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67 SDL_Delay(0);
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68 }
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69 }
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70
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71 void
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72 SDL_AtomicUnlock(SDL_SpinLock *lock)
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73 {
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74 /* Assuming atomic assignment operation and full memory barrier in lock */
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75 *lock = 0;
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76 }
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77
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78 /* vi: set ts=4 sw=4 expandtab: */