atomicops.h
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// ©2013-2015 Cameron Desrochers.
// Distributed under the simplified BSD license (see the license file that
// should have come with this header).
// Uses Jeff Preshing's semaphore implementation (under the terms of its
// separate zlib license, embedded below).
#pragma once
// Provides portable (VC++2010+, Intel ICC 13, GCC 4.7+, and anything C++11 compliant) implementation
// of low-level memory barriers, plus a few semi-portable utility macros (for inlining and alignment).
// Also has a basic atomic type (limited to hardware-supported atomics with no memory ordering guarantees).
// Uses the AE_* prefix for macros (historical reasons), and the "moodycamel" namespace for symbols.
#include <cassert>
#include <type_traits>
// Platform detection
#if defined(__INTEL_COMPILER)
#define AE_ICC
#elif defined(_MSC_VER)
#define AE_VCPP
#elif defined(__GNUC__)
#define AE_GCC
#endif
#if defined(_M_IA64) || defined(__ia64__)
#define AE_ARCH_IA64
#elif defined(_WIN64) || defined(__amd64__) || defined(_M_X64) || defined(__x86_64__)
#define AE_ARCH_X64
#elif defined(_M_IX86) || defined(__i386__)
#define AE_ARCH_X86
#elif defined(_M_PPC) || defined(__powerpc__)
#define AE_ARCH_PPC
#else
#define AE_ARCH_UNKNOWN
#endif
// AE_UNUSED
#define AE_UNUSED(x) ((void)x)
// AE_FORCEINLINE
#if defined(AE_VCPP) || defined(AE_ICC)
#define AE_FORCEINLINE __forceinline
#elif defined(AE_GCC)
//#define AE_FORCEINLINE __attribute__((always_inline))
#define AE_FORCEINLINE inline
#else
#define AE_FORCEINLINE inline
#endif
// AE_ALIGN
#if defined(AE_VCPP) || defined(AE_ICC)
#define AE_ALIGN(x) __declspec(align(x))
#elif defined(AE_GCC)
#define AE_ALIGN(x) __attribute__((aligned(x)))
#else
// Assume GCC compliant syntax...
#define AE_ALIGN(x) __attribute__((aligned(x)))
#endif
// Portable atomic fences implemented below:
namespace moodycamel {
enum memory_order {
memory_order_relaxed,
memory_order_acquire,
memory_order_release,
memory_order_acq_rel,
memory_order_seq_cst,
// memory_order_sync: Forces a full sync:
// #LoadLoad, #LoadStore, #StoreStore, and most significantly, #StoreLoad
memory_order_sync = memory_order_seq_cst
};
} // end namespace moodycamel
#if (defined(AE_VCPP) && (_MSC_VER < 1700 || defined(__cplusplus_cli))) || defined(AE_ICC)
// VS2010 and ICC13 don't support std::atomic_*_fence, implement our own fences
#include <intrin.h>
#if defined(AE_ARCH_X64) || defined(AE_ARCH_X86)
#define AeFullSync _mm_mfence
#define AeLiteSync _mm_mfence
#elif defined(AE_ARCH_IA64)
#define AeFullSync __mf
#define AeLiteSync __mf
#elif defined(AE_ARCH_PPC)
#include <ppcintrinsics.h>
#define AeFullSync __sync
#define AeLiteSync __lwsync
#endif
#ifdef AE_VCPP
#pragma warning(push)
#pragma warning(disable: 4365) // Disable erroneous 'conversion from long to unsigned int, signed/unsigned mismatch' error when using `assert`
#ifdef __cplusplus_cli
#pragma managed(push, off)
#endif
#endif
namespace moodycamel {
AE_FORCEINLINE void compiler_fence(memory_order order)
{
switch (order) {
case memory_order_relaxed: break;
case memory_order_acquire: _ReadBarrier(); break;
case memory_order_release: _WriteBarrier(); break;
case memory_order_acq_rel: _ReadWriteBarrier(); break;
case memory_order_seq_cst: _ReadWriteBarrier(); break;
default: assert(false);
}
}
// x86/x64 have a strong memory model -- all loads and stores have
// acquire and release semantics automatically (so only need compiler
// barriers for those).
#if defined(AE_ARCH_X86) || defined(AE_ARCH_X64)
AE_FORCEINLINE void fence(memory_order order)
{
switch (order) {
case memory_order_relaxed: break;
case memory_order_acquire: _ReadBarrier(); break;
case memory_order_release: _WriteBarrier(); break;
case memory_order_acq_rel: _ReadWriteBarrier(); break;
case memory_order_seq_cst:
_ReadWriteBarrier();
AeFullSync();
_ReadWriteBarrier();
break;
default: assert(false);
}
}
#else
AE_FORCEINLINE void fence(memory_order order)
{
// Non-specialized arch, use heavier memory barriers everywhere just in case :-(
switch (order) {
case memory_order_relaxed:
break;
case memory_order_acquire:
_ReadBarrier();
AeLiteSync();
_ReadBarrier();
break;
case memory_order_release:
_WriteBarrier();
AeLiteSync();
_WriteBarrier();
break;
case memory_order_acq_rel:
_ReadWriteBarrier();
AeLiteSync();
_ReadWriteBarrier();
break;
case memory_order_seq_cst:
_ReadWriteBarrier();
AeFullSync();
_ReadWriteBarrier();
break;
default: assert(false);
}
}
#endif
} // end namespace moodycamel
#else
// Use standard library of atomics
#include <atomic>
namespace moodycamel {
AE_FORCEINLINE void compiler_fence(memory_order order)
{
switch (order) {
case memory_order_relaxed: break;
case memory_order_acquire: std::atomic_signal_fence(std::memory_order_acquire); break;
case memory_order_release: std::atomic_signal_fence(std::memory_order_release); break;
case memory_order_acq_rel: std::atomic_signal_fence(std::memory_order_acq_rel); break;
case memory_order_seq_cst: std::atomic_signal_fence(std::memory_order_seq_cst); break;
default: assert(false);
}
}
AE_FORCEINLINE void fence(memory_order order)
{
switch (order) {
case memory_order_relaxed: break;
case memory_order_acquire: std::atomic_thread_fence(std::memory_order_acquire); break;
case memory_order_release: std::atomic_thread_fence(std::memory_order_release); break;
case memory_order_acq_rel: std::atomic_thread_fence(std::memory_order_acq_rel); break;
case memory_order_seq_cst: std::atomic_thread_fence(std::memory_order_seq_cst); break;
default: assert(false);
}
}
} // end namespace moodycamel
#endif
#if !defined(AE_VCPP) || (_MSC_VER >= 1700 && !defined(__cplusplus_cli))
#define AE_USE_STD_ATOMIC_FOR_WEAK_ATOMIC
#endif
#ifdef AE_USE_STD_ATOMIC_FOR_WEAK_ATOMIC
#include <atomic>
#endif
#include <utility>
// WARNING: *NOT* A REPLACEMENT FOR std::atomic. READ CAREFULLY:
// Provides basic support for atomic variables -- no memory ordering guarantees are provided.
// The guarantee of atomicity is only made for types that already have atomic load and store guarantees
// at the hardware level -- on most platforms this generally means aligned pointers and integers (only).
namespace moodycamel {
template<typename T>
class weak_atomic
{
public:
weak_atomic() { }
#ifdef AE_VCPP
#pragma warning(disable: 4100) // Get rid of (erroneous) 'unreferenced formal parameter' warning
#endif
template<typename U> weak_atomic(U&& x) : value(std::forward<U>(x)) { }
#ifdef __cplusplus_cli
// Work around bug with universal reference/nullptr combination that only appears when /clr is on
weak_atomic(nullptr_t) : value(nullptr) { }
#endif
weak_atomic(weak_atomic const& other) : value(other.value) { }
weak_atomic(weak_atomic&& other) : value(std::move(other.value)) { }
#ifdef AE_VCPP
#pragma warning(default: 4100)
#endif
AE_FORCEINLINE operator T() const { return load(); }
#ifndef AE_USE_STD_ATOMIC_FOR_WEAK_ATOMIC
template<typename U> AE_FORCEINLINE weak_atomic const& operator=(U&& x) { value = std::forward<U>(x); return *this; }
AE_FORCEINLINE weak_atomic const& operator=(weak_atomic const& other) { value = other.value; return *this; }
AE_FORCEINLINE T load() const { return value; }
AE_FORCEINLINE T fetch_add_acquire(T increment)
{
#if defined(AE_ARCH_X64) || defined(AE_ARCH_X86)
if (sizeof(T) == 4) return _InterlockedExchangeAdd((long volatile*)&value, (long)increment);
#if defined(_M_AMD64)
else if (sizeof(T) == 8) return _InterlockedExchangeAdd64((long long volatile*)&value, (long long)increment);
#endif
#else
#error Unsupported platform
#endif
assert(false && "T must be either a 32 or 64 bit type");
return value;
}
AE_FORCEINLINE T fetch_add_release(T increment)
{
#if defined(AE_ARCH_X64) || defined(AE_ARCH_X86)
if (sizeof(T) == 4) return _InterlockedExchangeAdd((long volatile*)&value, (long)increment);
#if defined(_M_AMD64)
else if (sizeof(T) == 8) return _InterlockedExchangeAdd64((long long volatile*)&value, (long long)increment);
#endif
#else
#error Unsupported platform
#endif
assert(false && "T must be either a 32 or 64 bit type");
return value;
}
#else
template<typename U>
AE_FORCEINLINE weak_atomic const& operator=(U&& x)
{
value.store(std::forward<U>(x), std::memory_order_relaxed);
return *this;
}
AE_FORCEINLINE weak_atomic const& operator=(weak_atomic const& other)
{
value.store(other.value.load(std::memory_order_relaxed), std::memory_order_relaxed);
return *this;
}
AE_FORCEINLINE T load() const { return value.load(std::memory_order_relaxed); }
AE_FORCEINLINE T fetch_add_acquire(T increment)
{
return value.fetch_add(increment, std::memory_order_acquire);
}
AE_FORCEINLINE T fetch_add_release(T increment)
{
return value.fetch_add(increment, std::memory_order_release);
}
#endif
private:
#ifndef AE_USE_STD_ATOMIC_FOR_WEAK_ATOMIC
// No std::atomic support, but still need to circumvent compiler optimizations.
// `volatile` will make memory access slow, but is guaranteed to be reliable.
volatile T value;
#else
std::atomic<T> value;
#endif
};
} // end namespace moodycamel
// Portable single-producer, single-consumer semaphore below:
#if defined(_WIN32)
// Avoid including windows.h in a header; we only need a handful of
// items, so we'll redeclare them here (this is relatively safe since
// the API generally has to remain stable between Windows versions).
// I know this is an ugly hack but it still beats polluting the global
// namespace with thousands of generic names or adding a .cpp for nothing.
extern "C" {
struct _SECURITY_ATTRIBUTES;
__declspec(dllimport) void* __stdcall CreateSemaphoreW(_SECURITY_ATTRIBUTES* lpSemaphoreAttributes, long lInitialCount, long lMaximumCount, const wchar_t* lpName);
__declspec(dllimport) int __stdcall CloseHandle(void* hObject);
__declspec(dllimport) unsigned long __stdcall WaitForSingleObject(void* hHandle, unsigned long dwMilliseconds);
__declspec(dllimport) int __stdcall ReleaseSemaphore(void* hSemaphore, long lReleaseCount, long* lpPreviousCount);
}
#elif defined(__MACH__)
#include <mach/mach.h>
#elif defined(__unix__)
#include <semaphore.h>
#endif
namespace moodycamel
{
// Code in the spsc_sema namespace below is an adaptation of Jeff Preshing's
// portable + lightweight semaphore implementations, originally from
// https://github.com/preshing/cpp11-on-multicore/blob/master/common/sema.h
// LICENSE:
// Copyright (c) 2015 Jeff Preshing
//
// 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 acknowledgement 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.
namespace spsc_sema
{
#if defined(_WIN32)
class Semaphore
{
private:
void* m_hSema;
Semaphore(const Semaphore& other);
Semaphore& operator=(const Semaphore& other);
public:
Semaphore(int initialCount = 0)
{
assert(initialCount >= 0);
const long maxLong = 0x7fffffff;
m_hSema = CreateSemaphoreW(nullptr, initialCount, maxLong, nullptr);
}
~Semaphore()
{
CloseHandle(m_hSema);
}
void wait()
{
const unsigned long infinite = 0xffffffff;
WaitForSingleObject(m_hSema, infinite);
}
void signal(int count = 1)
{
ReleaseSemaphore(m_hSema, count, nullptr);
}
};
#elif defined(__MACH__)
//---------------------------------------------------------
// Semaphore (Apple iOS and OSX)
// Can't use POSIX semaphores due to http://lists.apple.com/archives/darwin-kernel/2009/Apr/msg00010.html
//---------------------------------------------------------
class Semaphore
{
private:
semaphore_t m_sema;
Semaphore(const Semaphore& other);
Semaphore& operator=(const Semaphore& other);
public:
Semaphore(int initialCount = 0)
{
assert(initialCount >= 0);
semaphore_create(mach_task_self(), &m_sema, SYNC_POLICY_FIFO, initialCount);
}
~Semaphore()
{
semaphore_destroy(mach_task_self(), m_sema);
}
void wait()
{
semaphore_wait(m_sema);
}
void signal()
{
semaphore_signal(m_sema);
}
void signal(int count)
{
while (count-- > 0)
{
semaphore_signal(m_sema);
}
}
};
#elif defined(__unix__)
//---------------------------------------------------------
// Semaphore (POSIX, Linux)
//---------------------------------------------------------
class Semaphore
{
private:
sem_t m_sema;
Semaphore(const Semaphore& other);
Semaphore& operator=(const Semaphore& other);
public:
Semaphore(int initialCount = 0)
{
assert(initialCount >= 0);
sem_init(&m_sema, 0, initialCount);
}
~Semaphore()
{
sem_destroy(&m_sema);
}
void wait()
{
// http://stackoverflow.com/questions/2013181/gdb-causes-sem-wait-to-fail-with-eintr-error
int rc;
do
{
rc = sem_wait(&m_sema);
}
while (rc == -1 && errno == EINTR);
}
void signal()
{
sem_post(&m_sema);
}
void signal(int count)
{
while (count-- > 0)
{
sem_post(&m_sema);
}
}
};
#else
#error Unsupported platform! (No semaphore wrapper available)
#endif
//---------------------------------------------------------
// LightweightSemaphore
//---------------------------------------------------------
class LightweightSemaphore
{
public:
typedef std::make_signed<std::size_t>::type ssize_t;
private:
weak_atomic<ssize_t> m_count;
Semaphore m_sema;
void waitWithPartialSpinning()
{
ssize_t oldCount;
// Is there a better way to set the initial spin count?
// If we lower it to 1000, testBenaphore becomes 15x slower on my Core i7-5930K Windows PC,
// as threads start hitting the kernel semaphore.
int spin = 10000;
while (--spin >= 0)
{
if (m_count.load() > 0)
{
m_count.fetch_add_acquire(-1);
return;
}
compiler_fence(memory_order_acquire); // Prevent the compiler from collapsing the loop.
}
oldCount = m_count.fetch_add_acquire(-1);
if (oldCount <= 0)
{
m_sema.wait();
}
}
public:
LightweightSemaphore(ssize_t initialCount = 0) : m_count(initialCount)
{
assert(initialCount >= 0);
}
bool tryWait()
{
if (m_count.load() > 0)
{
m_count.fetch_add_acquire(-1);
return true;
}
return false;
}
void wait()
{
if (!tryWait())
waitWithPartialSpinning();
}
void signal(ssize_t count = 1)
{
assert(count >= 0);
ssize_t oldCount = m_count.fetch_add_release(count);
assert(oldCount >= -1);
if (oldCount < 0)
{
m_sema.signal(1);
}
}
ssize_t availableApprox() const
{
ssize_t count = m_count.load();
return count > 0 ? count : 0;
}
};
} // end namespace spsc_sema
} // end namespace moodycamel
#if defined(AE_VCPP) && (_MSC_VER < 1700 || defined(__cplusplus_cli))
#pragma warning(pop)
#ifdef __cplusplus_cli
#pragma managed(pop)
#endif
#endif
AE_FORCEINLINE
#define AE_FORCEINLINE
Definition atomicops.h:51
moodycamel::spsc_sema::LightweightSemaphore::tryWait
bool tryWait()
Definition atomicops.h:536
moodycamel::spsc_sema::LightweightSemaphore::ssize_t
std::make_signed< std::size_t >::type ssize_t
Definition atomicops.h:501
moodycamel::spsc_sema::LightweightSemaphore::wait
void wait()
Definition atomicops.h:546
moodycamel::spsc_sema::LightweightSemaphore::availableApprox
ssize_t availableApprox() const
Definition atomicops.h:563
moodycamel::spsc_sema::LightweightSemaphore::LightweightSemaphore
LightweightSemaphore(ssize_t initialCount=0)
Definition atomicops.h:531
moodycamel::spsc_sema::LightweightSemaphore::signal
void signal(ssize_t count=1)
Definition atomicops.h:552
moodycamel::weak_atomic
Definition atomicops.h:226
moodycamel::weak_atomic::fetch_add_release
AE_FORCEINLINE T fetch_add_release(T increment)
Definition atomicops.h:300
moodycamel::weak_atomic::load
AE_FORCEINLINE T load() const
Definition atomicops.h:293
moodycamel::weak_atomic::operator=
AE_FORCEINLINE weak_atomic const & operator=(U &&x)
Definition atomicops.h:281
moodycamel::weak_atomic::fetch_add_acquire
AE_FORCEINLINE T fetch_add_acquire(T increment)
Definition atomicops.h:295
moodycamel::weak_atomic::weak_atomic
weak_atomic(weak_atomic &&other)
Definition atomicops.h:238
moodycamel::weak_atomic::operator=
AE_FORCEINLINE weak_atomic const & operator=(weak_atomic const &other)
Definition atomicops.h:287
moodycamel::weak_atomic::weak_atomic
weak_atomic()
Definition atomicops.h:228
moodycamel::weak_atomic::weak_atomic
weak_atomic(weak_atomic const &other)
Definition atomicops.h:237
moodycamel::weak_atomic::weak_atomic
weak_atomic(U &&x)
Definition atomicops.h:232
moodycamel::spsc_sema
Definition atomicops.h:366
moodycamel
Definition atomicops.h:68
moodycamel::memory_order
memory_order
Definition atomicops.h:70
moodycamel::memory_order_acq_rel
@ memory_order_acq_rel
Definition atomicops.h:74
moodycamel::memory_order_seq_cst
@ memory_order_seq_cst
Definition atomicops.h:75
moodycamel::memory_order_acquire
@ memory_order_acquire
Definition atomicops.h:72
moodycamel::memory_order_relaxed
@ memory_order_relaxed
Definition atomicops.h:71
moodycamel::memory_order_sync
@ memory_order_sync
Definition atomicops.h:79
moodycamel::memory_order_release
@ memory_order_release
Definition atomicops.h:73
moodycamel::fence
AE_FORCEINLINE void fence(memory_order order)
Definition atomicops.h:193
moodycamel::compiler_fence
AE_FORCEINLINE void compiler_fence(memory_order order)
Definition atomicops.h:181