You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
296 lines
11 KiB
296 lines
11 KiB
4 years ago
|
/*
|
||
|
|
Simple DirectMedia Layer
|
||
|
|
Copyright (C) 1997-2020 Sam Lantinga <slouken@libsdl.org>
|
||
|
|
|
||
|
|
This software is provided 'as-is', without any express or implied
|
||
|
|
warranty. In no event will the authors be held liable for any damages
|
||
|
|
arising from the use of this software.
|
||
|
|
|
||
|
|
Permission is granted to anyone to use this software for any purpose,
|
||
|
|
including commercial applications, and to alter it and redistribute it
|
||
|
|
freely, subject to the following restrictions:
|
||
|
|
|
||
|
|
1. The origin of this software must not be misrepresented; you must not
|
||
|
|
claim that you wrote the original software. If you use this software
|
||
|
|
in a product, an acknowledgment in the product documentation would be
|
||
|
|
appreciated but is not required.
|
||
|
|
2. Altered source versions must be plainly marked as such, and must not be
|
||
|
|
misrepresented as being the original software.
|
||
|
|
3. This notice may not be removed or altered from any source distribution.
|
||
|
|
*/
|
||
|
|
|
||
|
|
/**
|
||
|
|
* \file SDL_atomic.h
|
||
|
|
*
|
||
|
|
* Atomic operations.
|
||
|
|
*
|
||
|
|
* IMPORTANT:
|
||
|
|
* If you are not an expert in concurrent lockless programming, you should
|
||
|
|
* only be using the atomic lock and reference counting functions in this
|
||
|
|
* file. In all other cases you should be protecting your data structures
|
||
|
|
* with full mutexes.
|
||
|
|
*
|
||
|
|
* The list of "safe" functions to use are:
|
||
|
|
* SDL_AtomicLock()
|
||
|
|
* SDL_AtomicUnlock()
|
||
|
|
* SDL_AtomicIncRef()
|
||
|
|
* SDL_AtomicDecRef()
|
||
|
|
*
|
||
|
|
* Seriously, here be dragons!
|
||
|
|
* ^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
||
|
|
*
|
||
|
|
* You can find out a little more about lockless programming and the
|
||
|
|
* subtle issues that can arise here:
|
||
|
|
* http://msdn.microsoft.com/en-us/library/ee418650%28v=vs.85%29.aspx
|
||
|
|
*
|
||
|
|
* There's also lots of good information here:
|
||
|
|
* http://www.1024cores.net/home/lock-free-algorithms
|
||
|
|
* http://preshing.com/
|
||
|
|
*
|
||
|
|
* These operations may or may not actually be implemented using
|
||
|
|
* processor specific atomic operations. When possible they are
|
||
|
|
* implemented as true processor specific atomic operations. When that
|
||
|
|
* is not possible the are implemented using locks that *do* use the
|
||
|
|
* available atomic operations.
|
||
|
|
*
|
||
|
|
* All of the atomic operations that modify memory are full memory barriers.
|
||
|
|
*/
|
||
|
|
|
||
|
|
#ifndef SDL_atomic_h_
|
||
|
|
#define SDL_atomic_h_
|
||
|
|
|
||
|
|
#include "SDL_stdinc.h"
|
||
|
|
#include "SDL_platform.h"
|
||
|
|
|
||
|
|
#include "begin_code.h"
|
||
|
|
|
||
|
|
/* Set up for C function definitions, even when using C++ */
|
||
|
|
#ifdef __cplusplus
|
||
|
|
extern "C" {
|
||
|
|
#endif
|
||
|
|
|
||
|
|
/**
|
||
|
|
* \name SDL AtomicLock
|
||
|
|
*
|
||
|
|
* The atomic locks are efficient spinlocks using CPU instructions,
|
||
|
|
* but are vulnerable to starvation and can spin forever if a thread
|
||
|
|
* holding a lock has been terminated. For this reason you should
|
||
|
|
* minimize the code executed inside an atomic lock and never do
|
||
|
|
* expensive things like API or system calls while holding them.
|
||
|
|
*
|
||
|
|
* The atomic locks are not safe to lock recursively.
|
||
|
|
*
|
||
|
|
* Porting Note:
|
||
|
|
* The spin lock functions and type are required and can not be
|
||
|
|
* emulated because they are used in the atomic emulation code.
|
||
|
|
*/
|
||
|
|
/* @{ */
|
||
|
|
|
||
|
|
typedef int SDL_SpinLock;
|
||
|
|
|
||
|
|
/**
|
||
|
|
* \brief Try to lock a spin lock by setting it to a non-zero value.
|
||
|
|
*
|
||
|
|
* \param lock Points to the lock.
|
||
|
|
*
|
||
|
|
* \return SDL_TRUE if the lock succeeded, SDL_FALSE if the lock is already held.
|
||
|
|
*/
|
||
|
|
extern DECLSPEC SDL_bool SDLCALL SDL_AtomicTryLock(SDL_SpinLock *lock);
|
||
|
|
|
||
|
|
/**
|
||
|
|
* \brief Lock a spin lock by setting it to a non-zero value.
|
||
|
|
*
|
||
|
|
* \param lock Points to the lock.
|
||
|
|
*/
|
||
|
|
extern DECLSPEC void SDLCALL SDL_AtomicLock(SDL_SpinLock *lock);
|
||
|
|
|
||
|
|
/**
|
||
|
|
* \brief Unlock a spin lock by setting it to 0. Always returns immediately
|
||
|
|
*
|
||
|
|
* \param lock Points to the lock.
|
||
|
|
*/
|
||
|
|
extern DECLSPEC void SDLCALL SDL_AtomicUnlock(SDL_SpinLock *lock);
|
||
|
|
|
||
|
|
/* @} *//* SDL AtomicLock */
|
||
|
|
|
||
|
|
|
||
|
|
/**
|
||
|
|
* The compiler barrier prevents the compiler from reordering
|
||
|
|
* reads and writes to globally visible variables across the call.
|
||
|
|
*/
|
||
|
|
#if defined(_MSC_VER) && (_MSC_VER > 1200) && !defined(__clang__)
|
||
|
|
void _ReadWriteBarrier(void);
|
||
|
|
#pragma intrinsic(_ReadWriteBarrier)
|
||
|
|
#define SDL_CompilerBarrier() _ReadWriteBarrier()
|
||
|
|
#elif (defined(__GNUC__) && !defined(__EMSCRIPTEN__)) || (defined(__SUNPRO_C) && (__SUNPRO_C >= 0x5120))
|
||
|
|
/* This is correct for all CPUs when using GCC or Solaris Studio 12.1+. */
|
||
|
|
#define SDL_CompilerBarrier() __asm__ __volatile__ ("" : : : "memory")
|
||
|
|
#elif defined(__WATCOMC__)
|
||
|
|
extern _inline void SDL_CompilerBarrier (void);
|
||
|
|
#pragma aux SDL_CompilerBarrier = "" parm [] modify exact [];
|
||
|
|
#else
|
||
|
|
#define SDL_CompilerBarrier() \
|
||
|
|
{ SDL_SpinLock _tmp = 0; SDL_AtomicLock(&_tmp); SDL_AtomicUnlock(&_tmp); }
|
||
|
|
#endif
|
||
|
|
|
||
|
|
/**
|
||
|
|
* Memory barriers are designed to prevent reads and writes from being
|
||
|
|
* reordered by the compiler and being seen out of order on multi-core CPUs.
|
||
|
|
*
|
||
|
|
* A typical pattern would be for thread A to write some data and a flag,
|
||
|
|
* and for thread B to read the flag and get the data. In this case you
|
||
|
|
* would insert a release barrier between writing the data and the flag,
|
||
|
|
* guaranteeing that the data write completes no later than the flag is
|
||
|
|
* written, and you would insert an acquire barrier between reading the
|
||
|
|
* flag and reading the data, to ensure that all the reads associated
|
||
|
|
* with the flag have completed.
|
||
|
|
*
|
||
|
|
* In this pattern you should always see a release barrier paired with
|
||
|
|
* an acquire barrier and you should gate the data reads/writes with a
|
||
|
|
* single flag variable.
|
||
|
|
*
|
||
|
|
* For more information on these semantics, take a look at the blog post:
|
||
|
|
* http://preshing.com/20120913/acquire-and-release-semantics
|
||
|
|
*/
|
||
|
|
extern DECLSPEC void SDLCALL SDL_MemoryBarrierReleaseFunction(void);
|
||
|
|
extern DECLSPEC void SDLCALL SDL_MemoryBarrierAcquireFunction(void);
|
||
|
|
|
||
|
|
#if defined(__GNUC__) && (defined(__powerpc__) || defined(__ppc__))
|
||
|
|
#define SDL_MemoryBarrierRelease() __asm__ __volatile__ ("lwsync" : : : "memory")
|
||
|
|
#define SDL_MemoryBarrierAcquire() __asm__ __volatile__ ("lwsync" : : : "memory")
|
||
|
|
#elif defined(__GNUC__) && defined(__aarch64__)
|
||
|
|
#define SDL_MemoryBarrierRelease() __asm__ __volatile__ ("dmb ish" : : : "memory")
|
||
|
|
#define SDL_MemoryBarrierAcquire() __asm__ __volatile__ ("dmb ish" : : : "memory")
|
||
|
|
#elif defined(__GNUC__) && defined(__arm__)
|
||
|
|
#if 0 /* defined(__LINUX__) || defined(__ANDROID__) */
|
||
|
|
/* Information from:
|
||
|
|
https://chromium.googlesource.com/chromium/chromium/+/trunk/base/atomicops_internals_arm_gcc.h#19
|
||
|
|
|
||
|
|
The Linux kernel provides a helper function which provides the right code for a memory barrier,
|
||
|
|
hard-coded at address 0xffff0fa0
|
||
|
|
*/
|
||
|
|
typedef void (*SDL_KernelMemoryBarrierFunc)();
|
||
|
|
#define SDL_MemoryBarrierRelease() ((SDL_KernelMemoryBarrierFunc)0xffff0fa0)()
|
||
|
|
#define SDL_MemoryBarrierAcquire() ((SDL_KernelMemoryBarrierFunc)0xffff0fa0)()
|
||
|
|
#elif 0 /* defined(__QNXNTO__) */
|
||
|
|
#include <sys/cpuinline.h>
|
||
|
|
|
||
|
|
#define SDL_MemoryBarrierRelease() __cpu_membarrier()
|
||
|
|
#define SDL_MemoryBarrierAcquire() __cpu_membarrier()
|
||
|
|
#else
|
||
|
|
#if defined(__ARM_ARCH_7__) || defined(__ARM_ARCH_7A__) || defined(__ARM_ARCH_7EM__) || defined(__ARM_ARCH_7R__) || defined(__ARM_ARCH_7M__) || defined(__ARM_ARCH_7S__) || defined(__ARM_ARCH_8A__)
|
||
|
|
#define SDL_MemoryBarrierRelease() __asm__ __volatile__ ("dmb ish" : : : "memory")
|
||
|
|
#define SDL_MemoryBarrierAcquire() __asm__ __volatile__ ("dmb ish" : : : "memory")
|
||
|
|
#elif defined(__ARM_ARCH_6__) || defined(__ARM_ARCH_6J__) || defined(__ARM_ARCH_6K__) || defined(__ARM_ARCH_6T2__) || defined(__ARM_ARCH_6Z__) || defined(__ARM_ARCH_6ZK__) || defined(__ARM_ARCH_5TE__)
|
||
|
|
#ifdef __thumb__
|
||
|
|
/* The mcr instruction isn't available in thumb mode, use real functions */
|
||
|
|
#define SDL_MEMORY_BARRIER_USES_FUNCTION
|
||
|
|
#define SDL_MemoryBarrierRelease() SDL_MemoryBarrierReleaseFunction()
|
||
|
|
#define SDL_MemoryBarrierAcquire() SDL_MemoryBarrierAcquireFunction()
|
||
|
|
#else
|
||
|
|
#define SDL_MemoryBarrierRelease() __asm__ __volatile__ ("mcr p15, 0, %0, c7, c10, 5" : : "r"(0) : "memory")
|
||
|
|
#define SDL_MemoryBarrierAcquire() __asm__ __volatile__ ("mcr p15, 0, %0, c7, c10, 5" : : "r"(0) : "memory")
|
||
|
|
#endif /* __thumb__ */
|
||
|
|
#else
|
||
|
|
#define SDL_MemoryBarrierRelease() __asm__ __volatile__ ("" : : : "memory")
|
||
|
|
#define SDL_MemoryBarrierAcquire() __asm__ __volatile__ ("" : : : "memory")
|
||
|
|
#endif /* __LINUX__ || __ANDROID__ */
|
||
|
|
#endif /* __GNUC__ && __arm__ */
|
||
|
|
#else
|
||
|
|
#if (defined(__SUNPRO_C) && (__SUNPRO_C >= 0x5120))
|
||
|
|
/* This is correct for all CPUs on Solaris when using Solaris Studio 12.1+. */
|
||
|
|
#include <mbarrier.h>
|
||
|
|
#define SDL_MemoryBarrierRelease() __machine_rel_barrier()
|
||
|
|
#define SDL_MemoryBarrierAcquire() __machine_acq_barrier()
|
||
|
|
#else
|
||
|
|
/* This is correct for the x86 and x64 CPUs, and we'll expand this over time. */
|
||
|
|
#define SDL_MemoryBarrierRelease() SDL_CompilerBarrier()
|
||
|
|
#define SDL_MemoryBarrierAcquire() SDL_CompilerBarrier()
|
||
|
|
#endif
|
||
|
|
#endif
|
||
|
|
|
||
|
|
/**
|
||
|
|
* \brief A type representing an atomic integer value. It is a struct
|
||
|
|
* so people don't accidentally use numeric operations on it.
|
||
|
|
*/
|
||
|
|
typedef struct { int value; } SDL_atomic_t;
|
||
|
|
|
||
|
|
/**
|
||
|
|
* \brief Set an atomic variable to a new value if it is currently an old value.
|
||
|
|
*
|
||
|
|
* \return SDL_TRUE if the atomic variable was set, SDL_FALSE otherwise.
|
||
|
|
*
|
||
|
|
* \note If you don't know what this function is for, you shouldn't use it!
|
||
|
|
*/
|
||
|
|
extern DECLSPEC SDL_bool SDLCALL SDL_AtomicCAS(SDL_atomic_t *a, int oldval, int newval);
|
||
|
|
|
||
|
|
/**
|
||
|
|
* \brief Set an atomic variable to a value.
|
||
|
|
*
|
||
|
|
* \return The previous value of the atomic variable.
|
||
|
|
*/
|
||
|
|
extern DECLSPEC int SDLCALL SDL_AtomicSet(SDL_atomic_t *a, int v);
|
||
|
|
|
||
|
|
/**
|
||
|
|
* \brief Get the value of an atomic variable
|
||
|
|
*/
|
||
|
|
extern DECLSPEC int SDLCALL SDL_AtomicGet(SDL_atomic_t *a);
|
||
|
|
|
||
|
|
/**
|
||
|
|
* \brief Add to an atomic variable.
|
||
|
|
*
|
||
|
|
* \return The previous value of the atomic variable.
|
||
|
|
*
|
||
|
|
* \note This same style can be used for any number operation
|
||
|
|
*/
|
||
|
|
extern DECLSPEC int SDLCALL SDL_AtomicAdd(SDL_atomic_t *a, int v);
|
||
|
|
|
||
|
|
/**
|
||
|
|
* \brief Increment an atomic variable used as a reference count.
|
||
|
|
*/
|
||
|
|
#ifndef SDL_AtomicIncRef
|
||
|
|
#define SDL_AtomicIncRef(a) SDL_AtomicAdd(a, 1)
|
||
|
|
#endif
|
||
|
|
|
||
|
|
/**
|
||
|
|
* \brief Decrement an atomic variable used as a reference count.
|
||
|
|
*
|
||
|
|
* \return SDL_TRUE if the variable reached zero after decrementing,
|
||
|
|
* SDL_FALSE otherwise
|
||
|
|
*/
|
||
|
|
#ifndef SDL_AtomicDecRef
|
||
|
|
#define SDL_AtomicDecRef(a) (SDL_AtomicAdd(a, -1) == 1)
|
||
|
|
#endif
|
||
|
|
|
||
|
|
/**
|
||
|
|
* \brief Set a pointer to a new value if it is currently an old value.
|
||
|
|
*
|
||
|
|
* \return SDL_TRUE if the pointer was set, SDL_FALSE otherwise.
|
||
|
|
*
|
||
|
|
* \note If you don't know what this function is for, you shouldn't use it!
|
||
|
|
*/
|
||
|
|
extern DECLSPEC SDL_bool SDLCALL SDL_AtomicCASPtr(void **a, void *oldval, void *newval);
|
||
|
|
|
||
|
|
/**
|
||
|
|
* \brief Set a pointer to a value atomically.
|
||
|
|
*
|
||
|
|
* \return The previous value of the pointer.
|
||
|
|
*/
|
||
|
|
extern DECLSPEC void* SDLCALL SDL_AtomicSetPtr(void **a, void* v);
|
||
|
|
|
||
|
|
/**
|
||
|
|
* \brief Get the value of a pointer atomically.
|
||
|
|
*/
|
||
|
|
extern DECLSPEC void* SDLCALL SDL_AtomicGetPtr(void **a);
|
||
|
|
|
||
|
|
/* Ends C function definitions when using C++ */
|
||
|
|
#ifdef __cplusplus
|
||
|
|
}
|
||
|
|
#endif
|
||
|
|
|
||
|
|
#include "close_code.h"
|
||
|
|
|
||
|
|
#endif /* SDL_atomic_h_ */
|
||
|
|
|
||
|
|
/* vi: set ts=4 sw=4 expandtab: */
|