This repository has been archived by the owner on Feb 11, 2021. It is now read-only.
SDL_spinlock.c
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/*
SDL - Simple DirectMedia Layer
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Copyright (C) 1997-2011 Sam Lantinga
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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"
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#include "SDL_mutex.h"
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#include "SDL_timer.h"
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/* Don't do the check for Visual Studio 2005, it's safe here */
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#ifdef __WIN32__
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#include "../core/windows/SDL_windows.h"
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/* This function is where all the magic happens... */
SDL_bool
SDL_AtomicTryLock(SDL_SpinLock *lock)
{
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#if SDL_ATOMIC_DISABLED
/* Terrible terrible damage */
static SDL_mutex *_spinlock_mutex;
if (!_spinlock_mutex) {
/* Race condition on first lock... */
_spinlock_mutex = SDL_CreateMutex();
}
SDL_mutexP(_spinlock_mutex);
if (*lock == 0) {
*lock = 1;
SDL_mutexV(_spinlock_mutex);
return SDL_TRUE;
} else {
SDL_mutexV(_spinlock_mutex);
return SDL_FALSE;
}
#elif defined(_MSC_VER)
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SDL_COMPILE_TIME_ASSERT(locksize, sizeof(*lock) == sizeof(long));
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return (InterlockedExchange((long*)lock, 1) == 0);
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#elif defined(__MACOSX__)
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return OSAtomicCompareAndSwap32Barrier(0, 1, lock);
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#elif HAVE_GCC_ATOMICS || HAVE_GCC_SYNC_LOCK_TEST_AND_SET
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return (__sync_lock_test_and_set(lock, 1) == 0);
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#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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#if defined(_MSC_VER)
_ReadWriteBarrier();
*lock = 0;
#elif HAVE_GCC_ATOMICS || HAVE_GCC_SYNC_LOCK_TEST_AND_SET
__sync_lock_release(lock);
#else
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*lock = 0;
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}
/* vi: set ts=4 sw=4 expandtab: */