atomicops.h

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// ©2013-2016 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>
#include <cerrno>
#include <cstdint>
#include <ctime>
 
// 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_NO_TSAN
#if defined(__has_feature)
#if __has_feature(thread_sanitizer)
#define AE_NO_TSAN __attribute__((no_sanitize("thread")))
#else
#define AE_NO_TSAN
#endif
#else
#define AE_NO_TSAN
#endif
 
 
// 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:
 
 
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
};
 
 
#if (defined(AE_VCPP) && (_MSC_VER < 1700 || defined(__cplusplus_cli))) || (defined(AE_ICC) && __INTEL_COMPILER < 1600)
// 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) AE_NO_TSAN
{
  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) AE_NO_TSAN
{
  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) AE_NO_TSAN
{
  // 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>
 
 
AE_FORCEINLINE void compiler_fence(memory_order order) AE_NO_TSAN
{
  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) AE_NO_TSAN
{
  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);
  }
}
 
 
#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).
template<typename T>
class weak_atomic
{
public:
  AE_NO_TSAN weak_atomic() { }
#ifdef AE_VCPP
#pragma warning(push)
#pragma warning(disable: 4100)    // Get rid of (erroneous) 'unreferenced formal parameter' warning
#endif
  template<typename U> AE_NO_TSAN 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
  AE_NO_TSAN weak_atomic(nullptr_t) : value(nullptr) {  }
#endif
  AE_NO_TSAN weak_atomic(weak_atomic const& other) : value(other.load()) {  }
  AE_NO_TSAN weak_atomic(weak_atomic&& other) : value(std::move(other.load())) {  }
#ifdef AE_VCPP
#pragma warning(pop)
#endif
 
  AE_FORCEINLINE operator T() const AE_NO_TSAN { return load(); }
 
  
#ifndef AE_USE_STD_ATOMIC_FOR_WEAK_ATOMIC
  template<typename U> AE_FORCEINLINE weak_atomic const& operator=(U&& x) AE_NO_TSAN { value = std::forward<U>(x); return *this; }
  AE_FORCEINLINE weak_atomic const& operator=(weak_atomic const& other) AE_NO_TSAN { value = other.value; return *this; }
  
  AE_FORCEINLINE T load() const AE_NO_TSAN { return value; }
  
  AE_FORCEINLINE T fetch_add_acquire(T increment) AE_NO_TSAN
  {
#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) AE_NO_TSAN
  {
#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) AE_NO_TSAN
  {
    value.store(std::forward<U>(x), std::memory_order_relaxed);
    return *this;
  }
  
  AE_FORCEINLINE weak_atomic const& operator=(weak_atomic const& other) AE_NO_TSAN
  {
    value.store(other.value.load(std::memory_order_relaxed), std::memory_order_relaxed);
    return *this;
  }
 
  AE_FORCEINLINE T load() const AE_NO_TSAN { return value.load(std::memory_order_relaxed); }
  
  AE_FORCEINLINE T fetch_add_acquire(T increment) AE_NO_TSAN
  {
    return value.fetch_add(increment, std::memory_order_acquire);
  }
  
  AE_FORCEINLINE T fetch_add_release(T increment) AE_NO_TSAN
  {
    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
};
 
 
 
 
// 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
 
  // 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:
        AE_NO_TSAN Semaphore(int initialCount = 0)
        {
            assert(initialCount >= 0);
            const long maxLong = 0x7fffffff;
            m_hSema = CreateSemaphoreW(nullptr, initialCount, maxLong, nullptr);
        }
 
        AE_NO_TSAN ~Semaphore()
        {
            CloseHandle(m_hSema);
        }
 
        void wait() AE_NO_TSAN
        {
          const unsigned long infinite = 0xffffffff;
            WaitForSingleObject(m_hSema, infinite);
        }
 
      bool try_wait() AE_NO_TSAN
      {
        const unsigned long RC_WAIT_TIMEOUT = 0x00000102;
        return WaitForSingleObject(m_hSema, 0) != RC_WAIT_TIMEOUT;
      }
 
      bool timed_wait(std::uint64_t usecs) AE_NO_TSAN
      {
        const unsigned long RC_WAIT_TIMEOUT = 0x00000102;
        return WaitForSingleObject(m_hSema, (unsigned long)(usecs / 1000)) != RC_WAIT_TIMEOUT;
      }
 
        void signal(int count = 1) AE_NO_TSAN
        {
            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:
        AE_NO_TSAN Semaphore(int initialCount = 0)
        {
            assert(initialCount >= 0);
            semaphore_create(mach_task_self(), &m_sema, SYNC_POLICY_FIFO, initialCount);
        }
 
        AE_NO_TSAN ~Semaphore()
        {
            semaphore_destroy(mach_task_self(), m_sema);
        }
 
        void wait() AE_NO_TSAN
        {
            semaphore_wait(m_sema);
        }
 
      bool try_wait() AE_NO_TSAN
      {
        return timed_wait(0);
      }
 
      bool timed_wait(std::int64_t timeout_usecs) AE_NO_TSAN
      {
        mach_timespec_t ts;
        ts.tv_sec = static_cast<unsigned int>(timeout_usecs / 1000000);
        ts.tv_nsec = (timeout_usecs % 1000000) * 1000;
 
        // added in OSX 10.10: https://developer.apple.com/library/prerelease/mac/documentation/General/Reference/APIDiffsMacOSX10_10SeedDiff/modules/Darwin.html
        kern_return_t rc = semaphore_timedwait(m_sema, ts);
 
        return rc != KERN_OPERATION_TIMED_OUT && rc != KERN_ABORTED;
      }
 
        void signal() AE_NO_TSAN
        {
            semaphore_signal(m_sema);
        }
 
        void signal(int count) AE_NO_TSAN
        {
            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:
        AE_NO_TSAN Semaphore(int initialCount = 0)
        {
            assert(initialCount >= 0);
            sem_init(&m_sema, 0, initialCount);
        }
 
        AE_NO_TSAN ~Semaphore()
        {
            sem_destroy(&m_sema);
        }
 
        void wait() AE_NO_TSAN
        {
            // 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);
        }
 
      bool try_wait() AE_NO_TSAN
      {
        int rc;
        do {
          rc = sem_trywait(&m_sema);
        } while (rc == -1 && errno == EINTR);
        return !(rc == -1 && errno == EAGAIN);
      }
 
      bool timed_wait(std::uint64_t usecs) AE_NO_TSAN
      {
        struct timespec ts;
        const int usecs_in_1_sec = 1000000;
        const int nsecs_in_1_sec = 1000000000;
        clock_gettime(CLOCK_REALTIME, &ts);
        ts.tv_sec += usecs / usecs_in_1_sec;
        ts.tv_nsec += (usecs % usecs_in_1_sec) * 1000;
        // sem_timedwait bombs if you have more than 1e9 in tv_nsec
        // so we have to clean things up before passing it in
        if (ts.tv_nsec >= nsecs_in_1_sec) {
          ts.tv_nsec -= nsecs_in_1_sec;
          ++ts.tv_sec;
        }
 
        int rc;
        do {
          rc = sem_timedwait(&m_sema, &ts);
        } while (rc == -1 && errno == EINTR);
        return !(rc == -1 && errno == ETIMEDOUT);
      }
 
        void signal() AE_NO_TSAN
        {
            sem_post(&m_sema);
        }
 
        void signal(int count) AE_NO_TSAN
        {
            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;
 
        bool waitWithPartialSpinning(std::int64_t timeout_usecs = -1) AE_NO_TSAN
        {
            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 true;
                }
                compiler_fence(memory_order_acquire);     // Prevent the compiler from collapsing the loop.
            }
            oldCount = m_count.fetch_add_acquire(-1);
        if (oldCount > 0)
          return true;
            if (timeout_usecs < 0)
        {
          m_sema.wait();
          return true;
        }
        if (m_sema.timed_wait(timeout_usecs))
          return true;
        // At this point, we've timed out waiting for the semaphore, but the
        // count is still decremented indicating we may still be waiting on
        // it. So we have to re-adjust the count, but only if the semaphore
        // wasn't signaled enough times for us too since then. If it was, we
        // need to release the semaphore too.
        while (true)
        {
          oldCount = m_count.fetch_add_release(1);
          if (oldCount < 0)
            return false;    // successfully restored things to the way they were
          // Oh, the producer thread just signaled the semaphore after all. Try again:
          oldCount = m_count.fetch_add_acquire(-1);
          if (oldCount > 0 && m_sema.try_wait())
            return true;
        }
        }
 
    public:
        AE_NO_TSAN LightweightSemaphore(ssize_t initialCount = 0) : m_count(initialCount)
        {
            assert(initialCount >= 0);
        }
 
        bool tryWait() AE_NO_TSAN
        {
            if (m_count.load() > 0)
            {
              m_count.fetch_add_acquire(-1);
              return true;
            }
            return false;
        }
 
        void wait() AE_NO_TSAN
        {
            if (!tryWait())
                waitWithPartialSpinning();
        }
 
      bool wait(std::int64_t timeout_usecs) AE_NO_TSAN
      {
        return tryWait() || waitWithPartialSpinning(timeout_usecs);
      }
 
        void signal(ssize_t count = 1) AE_NO_TSAN
        {
          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 AE_NO_TSAN
        {
          ssize_t count = m_count.load();
          return count > 0 ? count : 0;
        }
    };
  } // end namespace spsc_sema
 
#if defined(AE_VCPP) && (_MSC_VER < 1700 || defined(__cplusplus_cli))
#pragma warning(pop)
#ifdef __cplusplus_cli
#pragma managed(pop)
#endif
#endif