b0e0f61c7e
Changed the CAS return value to bool, so it's efficient with OSAtomicCompareAndSwap32Barrier() Added an atomic test adapted from code by Michael Davidsaver
86 lines
2.3 KiB
C
86 lines
2.3 KiB
C
/*
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SDL - Simple DirectMedia Layer
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Copyright (C) 1997-2010 Sam Lantinga
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This library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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This library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with this library; if not, write to the Free Software
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Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
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Sam Lantinga
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slouken@libsdl.org
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*/
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#include "SDL_stdinc.h"
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#include "SDL_atomic.h"
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#include "SDL_timer.h"
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#if defined(__WIN32__)
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#define WIN32_LEAN_AND_MEAN
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#include <windows.h>
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#elif defined(__MACOSX__)
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#include <libkern/OSAtomic.h>
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#endif
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/* This function is where all the magic happens... */
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SDL_bool
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SDL_AtomicTryLock(SDL_SpinLock *lock)
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{
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#if defined(__WIN32__)
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return (InterlockedExchange(lock, 1) == 0);
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#elif defined(__MACOSX__)
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return OSAtomicCompareAndSwap32Barrier(0, 1, lock);
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#elif defined(HAVE_GCC_ATOMICS)
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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;
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__asm__ __volatile__ (
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"swp %0, %1, [%2]\n"
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: "=&r,&r" (result) : "r,0" (1), "r,r" (lock) : "memory");
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return (result == 0);
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#elif defined(__GNUC__) && defined(__arm__)
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int result;
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__asm__ __volatile__ (
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"ldrex %0, [%2]\nteq %0, #0\nstrexeq %0, %1, [%2]"
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: "=&r" (result) : "r" (1), "r" (lock) : "cc", "memory");
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return (result == 0);
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#else
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/* Need CPU instructions for spinlock here! */
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__need_spinlock_implementation__
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#endif
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}
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void
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SDL_AtomicLock(SDL_SpinLock *lock)
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{
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/* FIXME: Should we have an eventual timeout? */
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while (!SDL_AtomicTryLock(lock)) {
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SDL_Delay(0);
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}
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}
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void
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SDL_AtomicUnlock(SDL_SpinLock *lock)
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{
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/* Assuming atomic assignment operation and full memory barrier in lock */
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*lock = 0;
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}
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/* vi: set ts=4 sw=4 expandtab: */
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