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SDL_spinlock.c
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/*
SDL - Simple DirectMedia Layer
Copyright (C) 1997-2010 Sam Lantinga
This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
This library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with this library; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
Sam Lantinga
slouken@libsdl.org
*/
#include "SDL_stdinc.h"
#include "SDL_atomic.h"
#include "SDL_timer.h"
/* This function is where all the magic happens... */
SDL_bool
SDL_AtomicTryLock(SDL_SpinLock *lock)
{
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#if defined(_MSC_VER)
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SDL_COMPILE_TIME_ASSERT(locksize, sizeof(*lock) == sizeof(long));
return (_InterlockedExchange((long*)lock, 1) == 0);
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#elif defined(__MACOSX__)
return OSAtomicCompareAndSwap32Barrier(0, 1, lock);
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#elif defined(HAVE_GCC_ATOMICS)
return (__sync_lock_test_and_set(lock, 1) == 0);
#elif defined(__GNUC__) && defined(__arm__) && defined(__ARM_ARCH_5__)
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int result;
__asm__ __volatile__ (
"swp %0, %1, [%2]\n"
: "=&r,&r" (result) : "r,0" (1), "r,r" (lock) : "memory");
return (result == 0);
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#elif defined(__GNUC__) && defined(__arm__)
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int result;
__asm__ __volatile__ (
"ldrex %0, [%2]\nteq %0, #0\nstrexeq %0, %1, [%2]"
: "=&r" (result) : "r" (1), "r" (lock) : "cc", "memory");
return (result == 0);
#else
/* Need CPU instructions for spinlock here! */
__need_spinlock_implementation__
#endif
}
void
SDL_AtomicLock(SDL_SpinLock *lock)
{
/* FIXME: Should we have an eventual timeout? */
while (!SDL_AtomicTryLock(lock)) {
SDL_Delay(0);
}
}
void
SDL_AtomicUnlock(SDL_SpinLock *lock)
{
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/* Assuming atomic assignment operation and full memory barrier in lock */
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*lock = 0;
}
/* vi: set ts=4 sw=4 expandtab: */