mirror of
https://github.com/Relintai/sdl2_frt.git
synced 2025-02-04 11:15:57 +01:00
b72938c861
An existing hint lets apps that don't need the timer resolution changed avoid this, to save battery, etc, but this fixes several problems in timing, audio callbacks not firing fast enough, etc. Fixes Bugzilla #2944.
136 lines
4.0 KiB
C
136 lines
4.0 KiB
C
/*
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Simple DirectMedia Layer
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Copyright (C) 1997-2014 Sam Lantinga <slouken@libsdl.org>
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This software is provided 'as-is', without any express or implied
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warranty. In no event will the authors be held liable for any damages
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arising from the use of this software.
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Permission is granted to anyone to use this software for any purpose,
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including commercial applications, and to alter it and redistribute it
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freely, subject to the following restrictions:
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1. The origin of this software must not be misrepresented; you must not
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claim that you wrote the original software. If you use this software
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in a product, an acknowledgment in the product documentation would be
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appreciated but is not required.
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2. Altered source versions must be plainly marked as such, and must not be
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misrepresented as being the original software.
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3. This notice may not be removed or altered from any source distribution.
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*/
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#include "../SDL_internal.h"
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#if defined(__WIN32__) || defined(__WINRT__)
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#include "../core/windows/SDL_windows.h"
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#endif
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#include "SDL_atomic.h"
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#include "SDL_mutex.h"
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#include "SDL_timer.h"
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#if !defined(HAVE_GCC_ATOMICS) && defined(__SOLARIS__)
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#include <atomic.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 SDL_ATOMIC_DISABLED
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/* Terrible terrible damage */
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static SDL_mutex *_spinlock_mutex;
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if (!_spinlock_mutex) {
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/* Race condition on first lock... */
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_spinlock_mutex = SDL_CreateMutex();
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}
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SDL_LockMutex(_spinlock_mutex);
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if (*lock == 0) {
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*lock = 1;
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SDL_UnlockMutex(_spinlock_mutex);
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return SDL_TRUE;
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} else {
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SDL_UnlockMutex(_spinlock_mutex);
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return SDL_FALSE;
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}
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#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 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__) && \
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(defined(__ARM_ARCH_4__) || defined(__ARM_ARCH_4T__) || \
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defined(__ARM_ARCH_5__) || defined(__ARM_ARCH_5TE__) || \
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defined(__ARM_ARCH_5TEJ__))
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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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#elif defined(__GNUC__) && (defined(__i386__) || defined(__x86_64__))
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int result;
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__asm__ __volatile__(
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"lock ; xchgl %0, (%1)\n"
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: "=r" (result) : "r" (lock), "0" (1) : "cc", "memory");
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return (result == 0);
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#elif defined(__MACOSX__) || defined(__IPHONEOS__)
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/* Maybe used for PowerPC, but the Intel asm or gcc atomics are favored. */
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return OSAtomicCompareAndSwap32Barrier(0, 1, lock);
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#elif defined(__SOLARIS__) && defined(_LP64)
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/* Used for Solaris with non-gcc compilers. */
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return (SDL_bool) ((int) atomic_cas_64((volatile uint64_t*)lock, 0, 1) == 0);
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#elif defined(__SOLARIS__) && !defined(_LP64)
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/* Used for Solaris with non-gcc compilers. */
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return (SDL_bool) ((int) atomic_cas_32((volatile uint32_t*)lock, 0, 1) == 0);
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#else
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#error Please implement for your platform.
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return SDL_FALSE;
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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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#if defined(_MSC_VER)
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_ReadWriteBarrier();
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*lock = 0;
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#elif HAVE_GCC_ATOMICS || HAVE_GCC_SYNC_LOCK_TEST_AND_SET
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__sync_lock_release(lock);
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#elif defined(__SOLARIS__)
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/* Used for Solaris when not using gcc. */
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*lock = 0;
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membar_producer();
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#else
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*lock = 0;
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#endif
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}
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/* vi: set ts=4 sw=4 expandtab: */
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