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Updated moodycamel's concurrent queue

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This commit is contained in:
Paul Ferrand 2020-01-03 09:47:14 +01:00
parent 90bb90c398
commit 543931d185
3 changed files with 470 additions and 431 deletions
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411
src/external/moodycamel/blockingconcurrentqueue.h vendored
View file

@ -7,413 +7,16 @@
#pragma once
#include "concurrentqueue.h"
#include "lightweightsemaphore.h"
#include <type_traits>
#include <cerrno>
#include <memory>
#include <chrono>
#include <ctime>
#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
{
namespace details
{
// Code in the mpmc_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 mpmc_sema
{
#if defined(_WIN32)
class Semaphore
{
private:
void* m_hSema;
Semaphore(const Semaphore& other) MOODYCAMEL_DELETE_FUNCTION;
Semaphore& operator=(const Semaphore& other) MOODYCAMEL_DELETE_FUNCTION;
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);
}
bool try_wait()
{
const unsigned long RC_WAIT_TIMEOUT = 0x00000102;
return WaitForSingleObject(m_hSema, 0) != RC_WAIT_TIMEOUT;
}
bool timed_wait(std::uint64_t usecs)
{
const unsigned long RC_WAIT_TIMEOUT = 0x00000102;
return WaitForSingleObject(m_hSema, (unsigned long)(usecs / 1000)) != RC_WAIT_TIMEOUT;
}
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) MOODYCAMEL_DELETE_FUNCTION;
Semaphore& operator=(const Semaphore& other) MOODYCAMEL_DELETE_FUNCTION;
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);
}
bool try_wait()
{
return timed_wait(0);
}
bool timed_wait(std::uint64_t timeout_usecs)
{
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()
{
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) MOODYCAMEL_DELETE_FUNCTION;
Semaphore& operator=(const Semaphore& other) MOODYCAMEL_DELETE_FUNCTION;
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);
}
bool try_wait()
{
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)
{
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()
{
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:
std::atomic<ssize_t> m_count;
Semaphore m_sema;
bool waitWithPartialSpinning(std::int64_t timeout_usecs = -1)
{
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)
{
oldCount = m_count.load(std::memory_order_relaxed);
if ((oldCount > 0) && m_count.compare_exchange_strong(oldCount, oldCount - 1, std::memory_order_acquire, std::memory_order_relaxed))
return true;
std::atomic_signal_fence(std::memory_order_acquire); // Prevent the compiler from collapsing the loop.
}
oldCount = m_count.fetch_sub(1, std::memory_order_acquire);
if (oldCount > 0)
return true;
if (timeout_usecs < 0)
{
m_sema.wait();
return true;
}
if (m_sema.timed_wait((std::uint64_t)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.load(std::memory_order_acquire);
if (oldCount >= 0 && m_sema.try_wait())
return true;
if (oldCount < 0 && m_count.compare_exchange_strong(oldCount, oldCount + 1, std::memory_order_relaxed, std::memory_order_relaxed))
return false;
}
}
ssize_t waitManyWithPartialSpinning(ssize_t max, std::int64_t timeout_usecs = -1)
{
assert(max > 0);
ssize_t oldCount;
int spin = 10000;
while (--spin >= 0)
{
oldCount = m_count.load(std::memory_order_relaxed);
if (oldCount > 0)
{
ssize_t newCount = oldCount > max ? oldCount - max : 0;
if (m_count.compare_exchange_strong(oldCount, newCount, std::memory_order_acquire, std::memory_order_relaxed))
return oldCount - newCount;
}
std::atomic_signal_fence(std::memory_order_acquire);
}
oldCount = m_count.fetch_sub(1, std::memory_order_acquire);
if (oldCount <= 0)
{
if (timeout_usecs < 0)
m_sema.wait();
else if (!m_sema.timed_wait((std::uint64_t)timeout_usecs))
{
while (true)
{
oldCount = m_count.load(std::memory_order_acquire);
if (oldCount >= 0 && m_sema.try_wait())
break;
if (oldCount < 0 && m_count.compare_exchange_strong(oldCount, oldCount + 1, std::memory_order_relaxed, std::memory_order_relaxed))
return 0;
}
}
}
if (max > 1)
return 1 + tryWaitMany(max - 1);
return 1;
}
public:
LightweightSemaphore(ssize_t initialCount = 0) : m_count(initialCount)
{
assert(initialCount >= 0);
}
bool tryWait()
{
ssize_t oldCount = m_count.load(std::memory_order_relaxed);
while (oldCount > 0)
{
if (m_count.compare_exchange_weak(oldCount, oldCount - 1, std::memory_order_acquire, std::memory_order_relaxed))
return true;
}
return false;
}
void wait()
{
if (!tryWait())
waitWithPartialSpinning();
}
bool wait(std::int64_t timeout_usecs)
{
return tryWait() || waitWithPartialSpinning(timeout_usecs);
}
// Acquires between 0 and (greedily) max, inclusive
ssize_t tryWaitMany(ssize_t max)
{
assert(max >= 0);
ssize_t oldCount = m_count.load(std::memory_order_relaxed);
while (oldCount > 0)
{
ssize_t newCount = oldCount > max ? oldCount - max : 0;
if (m_count.compare_exchange_weak(oldCount, newCount, std::memory_order_acquire, std::memory_order_relaxed))
return oldCount - newCount;
}
return 0;
}
// Acquires at least one, and (greedily) at most max
ssize_t waitMany(ssize_t max, std::int64_t timeout_usecs)
{
assert(max >= 0);
ssize_t result = tryWaitMany(max);
if (result == 0 && max > 0)
result = waitManyWithPartialSpinning(max, timeout_usecs);
return result;
}
ssize_t waitMany(ssize_t max)
{
ssize_t result = waitMany(max, -1);
assert(result > 0);
return result;
}
void signal(ssize_t count = 1)
{
assert(count >= 0);
ssize_t oldCount = m_count.fetch_add(count, std::memory_order_release);
ssize_t toRelease = -oldCount < count ? -oldCount : count;
if (toRelease > 0)
{
m_sema.signal((int)toRelease);
}
}
ssize_t availableApprox() const
{
ssize_t count = m_count.load(std::memory_order_relaxed);
return count > 0 ? count : 0;
}
};
} // end namespace mpmc_sema
} // end namespace details
// This is a blocking version of the queue. It has an almost identical interface to
// the normal non-blocking version, with the addition of various wait_dequeue() methods
// and the removal of producer-specific dequeue methods.
@ -422,7 +25,7 @@ class BlockingConcurrentQueue
{
private:
typedef ::moodycamel::ConcurrentQueue<T, Traits> ConcurrentQueue;
typedef details::mpmc_sema::LightweightSemaphore LightweightSemaphore;
typedef ::moodycamel::LightweightSemaphore LightweightSemaphore;
public:
typedef typename ConcurrentQueue::producer_token_t producer_token_t;
@ -754,7 +357,9 @@ public:
template<typename U>
inline void wait_dequeue(U& item)
{
sema->wait();
while (!sema->wait()) {
continue;
}
while (!inner.try_dequeue(item)) {
continue;
}
@ -795,7 +400,9 @@ public:
template<typename U>
inline void wait_dequeue(consumer_token_t& token, U& item)
{
sema->wait();
while (!sema->wait()) {
continue;
}
while (!inner.try_dequeue(token, item)) {
continue;
}

78
src/external/moodycamel/concurrentqueue.h vendored
View file

@ -146,7 +146,7 @@ namespace moodycamel { namespace details {
typedef std::uintptr_t thread_id_t;
static const thread_id_t invalid_thread_id = 0; // Address can't be nullptr
static const thread_id_t invalid_thread_id2 = 1; // Member accesses off a null pointer are also generally invalid. Plus it's not aligned.
static inline thread_id_t thread_id() { static MOODYCAMEL_THREADLOCAL int x; return reinterpret_cast<thread_id_t>(&x); }
inline thread_id_t thread_id() { static MOODYCAMEL_THREADLOCAL int x; return reinterpret_cast<thread_id_t>(&x); }
} }
#endif
@ -214,6 +214,19 @@ namespace moodycamel { namespace details {
#endif
#endif
#ifndef MOODYCAMEL_ALIGNAS
// VS2013 doesn't support alignas or alignof
#if defined(_MSC_VER) && _MSC_VER <= 1800
#define MOODYCAMEL_ALIGNAS(alignment) __declspec(align(alignment))
#define MOODYCAMEL_ALIGNOF(obj) __alignof(obj)
#else
#define MOODYCAMEL_ALIGNAS(alignment) alignas(alignment)
#define MOODYCAMEL_ALIGNOF(obj) alignof(obj)
#endif
#endif
// Compiler-specific likely/unlikely hints
namespace moodycamel { namespace details {
#if defined(__GNUC__)
@ -1583,20 +1596,8 @@ private:
inline T const* operator[](index_t idx) const MOODYCAMEL_NOEXCEPT { return static_cast<T const*>(static_cast<void const*>(elements)) + static_cast<size_t>(idx & static_cast<index_t>(BLOCK_SIZE - 1)); }
private:
// IMPORTANT: This must be the first member in Block, so that if T depends on the alignment of
// addresses returned by malloc, that alignment will be preserved. Apparently clang actually
// generates code that uses this assumption for AVX instructions in some cases. Ideally, we
// should also align Block to the alignment of T in case it's higher than malloc's 16-byte
// alignment, but this is hard to do in a cross-platform way. Assert for this case:
static_assert(std::alignment_of<T>::value <= std::alignment_of<details::max_align_t>::value, "The queue does not support super-aligned types at this time");
// Additionally, we need the alignment of Block itself to be a multiple of max_align_t since
// otherwise the appropriate padding will not be added at the end of Block in order to make
// arrays of Blocks all be properly aligned (not just the first one). We use a union to force
// this.
union {
char elements[sizeof(T) * BLOCK_SIZE];
details::max_align_t dummy;
};
static_assert(std::alignment_of<T>::value <= sizeof(T), "The queue does not support types with an alignment greater than their size at this time");
MOODYCAMEL_ALIGNAS(MOODYCAMEL_ALIGNOF(T)) char elements[sizeof(T) * BLOCK_SIZE];
public:
Block* next;
std::atomic<size_t> elementsCompletelyDequeued;
@ -1611,7 +1612,7 @@ private:
void* owner;
#endif
};
static_assert(std::alignment_of<Block>::value >= std::alignment_of<details::max_align_t>::value, "Internal error: Blocks must be at least as aligned as the type they are wrapping");
static_assert(std::alignment_of<Block>::value >= std::alignment_of<T>::value, "Internal error: Blocks must be at least as aligned as the type they are wrapping");
#ifdef MCDBGQ_TRACKMEM
@ -3311,6 +3312,7 @@ private:
auto hashedId = details::hash_thread_id(id);
auto mainHash = implicitProducerHash.load(std::memory_order_acquire);
assert(mainHash != nullptr); // silence clang-tidy and MSVC warnings (hash cannot be null)
for (auto hash = mainHash; hash != nullptr; hash = hash->prev) {
// Look for the id in this hash
auto index = hashedId;
@ -3489,18 +3491,38 @@ private:
// Utility functions
//////////////////////////////////
template<typename TAlign>
static inline void* aligned_malloc(size_t size)
{
if (std::alignment_of<TAlign>::value <= std::alignment_of<details::max_align_t>::value)
return (Traits::malloc)(size);
size_t alignment = std::alignment_of<TAlign>::value;
void* raw = (Traits::malloc)(size + alignment - 1 + sizeof(void*));
if (!raw)
return nullptr;
char* ptr = details::align_for<TAlign>(reinterpret_cast<char*>(raw) + sizeof(void*));
*(reinterpret_cast<void**>(ptr) - 1) = raw;
return ptr;
}
template<typename TAlign>
static inline void aligned_free(void* ptr)
{
if (std::alignment_of<TAlign>::value <= std::alignment_of<details::max_align_t>::value)
return (Traits::free)(ptr);
(Traits::free)(ptr ? *(reinterpret_cast<void**>(ptr) - 1) : nullptr);
}
template<typename U>
static inline U* create_array(size_t count)
{
assert(count > 0);
auto p = static_cast<U*>((Traits::malloc)(sizeof(U) * count));
if (p == nullptr) {
U* p = static_cast<U*>(aligned_malloc<U>(sizeof(U) * count));
if (p == nullptr)
return nullptr;
}
for (size_t i = 0; i != count; ++i) {
for (size_t i = 0; i != count; ++i)
new (p + i) U();
}
return p;
}
@ -3509,34 +3531,32 @@ private:
{
if (p != nullptr) {
assert(count > 0);
for (size_t i = count; i != 0; ) {
for (size_t i = count; i != 0; )
(p + --i)->~U();
}
(Traits::free)(p);
}
aligned_free<U>(p);
}
template<typename U>
static inline U* create()
{
auto p = (Traits::malloc)(sizeof(U));
void* p = aligned_malloc<U>(sizeof(U));
return p != nullptr ? new (p) U : nullptr;
}
template<typename U, typename A1>
static inline U* create(A1&& a1)
{
auto p = (Traits::malloc)(sizeof(U));
void* p = aligned_malloc<U>(sizeof(U));
return p != nullptr ? new (p) U(std::forward<A1>(a1)) : nullptr;
}
template<typename U>
static inline void destroy(U* p)
{
if (p != nullptr) {
if (p != nullptr)
p->~U();
}
(Traits::free)(p);
aligned_free<U>(p);
}
private:

412
src/external/moodycamel/lightweightsemaphore.h vendored Normal file
View file

@ -0,0 +1,412 @@
// Provides an efficient implementation of a semaphore (LightweightSemaphore).
// This is an extension of Jeff Preshing's sempahore implementation (licensed
// under the terms of its separate zlib license) that has been adapted and
// extended by Cameron Desrochers.
#pragma once
#include <cstddef> // For std::size_t
#include <atomic>
#include <type_traits> // For std::make_signed<T>
#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
{
namespace details
{
// Code in the mpmc_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.
#if defined(_WIN32)
class Semaphore
{
private:
void* m_hSema;
Semaphore(const Semaphore& other) MOODYCAMEL_DELETE_FUNCTION;
Semaphore& operator=(const Semaphore& other) MOODYCAMEL_DELETE_FUNCTION;
public:
Semaphore(int initialCount = 0)
{
assert(initialCount >= 0);
const long maxLong = 0x7fffffff;
m_hSema = CreateSemaphoreW(nullptr, initialCount, maxLong, nullptr);
assert(m_hSema);
}
~Semaphore()
{
CloseHandle(m_hSema);
}
bool wait()
{
const unsigned long infinite = 0xffffffff;
return WaitForSingleObject(m_hSema, infinite) == 0;
}
bool try_wait()
{
return WaitForSingleObject(m_hSema, 0) == 0;
}
bool timed_wait(std::uint64_t usecs)
{
return WaitForSingleObject(m_hSema, (unsigned long)(usecs / 1000)) == 0;
}
void signal(int count = 1)
{
while (!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) MOODYCAMEL_DELETE_FUNCTION;
Semaphore& operator=(const Semaphore& other) MOODYCAMEL_DELETE_FUNCTION;
public:
Semaphore(int initialCount = 0)
{
assert(initialCount >= 0);
kern_return_t rc = semaphore_create(mach_task_self(), &m_sema, SYNC_POLICY_FIFO, initialCount);
assert(rc == KERN_SUCCESS);
}
~Semaphore()
{
semaphore_destroy(mach_task_self(), m_sema);
}
bool wait()
{
return semaphore_wait(m_sema) == KERN_SUCCESS;
}
bool try_wait()
{
return timed_wait(0);
}
bool timed_wait(std::uint64_t timeout_usecs)
{
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_SUCCESS;
}
void signal()
{
while (semaphore_signal(m_sema) != KERN_SUCCESS);
}
void signal(int count)
{
while (count-- > 0)
{
while (semaphore_signal(m_sema) != KERN_SUCCESS);
}
}
};
#elif defined(__unix__)
//---------------------------------------------------------
// Semaphore (POSIX, Linux)
//---------------------------------------------------------
class Semaphore
{
private:
sem_t m_sema;
Semaphore(const Semaphore& other) MOODYCAMEL_DELETE_FUNCTION;
Semaphore& operator=(const Semaphore& other) MOODYCAMEL_DELETE_FUNCTION;
public:
Semaphore(int initialCount = 0)
{
assert(initialCount >= 0);
int rc = sem_init(&m_sema, 0, initialCount);
assert(rc == 0);
}
~Semaphore()
{
sem_destroy(&m_sema);
}
bool 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);
return rc == 0;
}
bool try_wait()
{
int rc;
do {
rc = sem_trywait(&m_sema);
} while (rc == -1 && errno == EINTR);
return rc == 0;
}
bool timed_wait(std::uint64_t usecs)
{
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 == 0;
}
void signal()
{
while (sem_post(&m_sema) == -1);
}
void signal(int count)
{
while (count-- > 0)
{
while (sem_post(&m_sema) == -1);
}
}
};
#else
#error Unsupported platform! (No semaphore wrapper available)
#endif
} // end namespace details
//---------------------------------------------------------
// LightweightSemaphore
//---------------------------------------------------------
class LightweightSemaphore
{
public:
typedef std::make_signed<std::size_t>::type ssize_t;
private:
std::atomic<ssize_t> m_count;
details::Semaphore m_sema;
bool waitWithPartialSpinning(std::int64_t timeout_usecs = -1)
{
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)
{
oldCount = m_count.load(std::memory_order_relaxed);
if ((oldCount > 0) && m_count.compare_exchange_strong(oldCount, oldCount - 1, std::memory_order_acquire, std::memory_order_relaxed))
return true;
std::atomic_signal_fence(std::memory_order_acquire); // Prevent the compiler from collapsing the loop.
}
oldCount = m_count.fetch_sub(1, std::memory_order_acquire);
if (oldCount > 0)
return true;
if (timeout_usecs < 0)
return m_sema.wait();
if (m_sema.timed_wait((std::uint64_t)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.load(std::memory_order_acquire);
if (oldCount >= 0 && m_sema.try_wait())
return true;
if (oldCount < 0 && m_count.compare_exchange_strong(oldCount, oldCount + 1, std::memory_order_relaxed, std::memory_order_relaxed))
return false;
}
}
ssize_t waitManyWithPartialSpinning(ssize_t max, std::int64_t timeout_usecs = -1)
{
assert(max > 0);
ssize_t oldCount;
int spin = 10000;
while (--spin >= 0)
{
oldCount = m_count.load(std::memory_order_relaxed);
if (oldCount > 0)
{
ssize_t newCount = oldCount > max ? oldCount - max : 0;
if (m_count.compare_exchange_strong(oldCount, newCount, std::memory_order_acquire, std::memory_order_relaxed))
return oldCount - newCount;
}
std::atomic_signal_fence(std::memory_order_acquire);
}
oldCount = m_count.fetch_sub(1, std::memory_order_acquire);
if (oldCount <= 0)
{
if (timeout_usecs < 0)
{
if (!m_sema.wait())
return 0;
}
else if (!m_sema.timed_wait((std::uint64_t)timeout_usecs))
{
while (true)
{
oldCount = m_count.load(std::memory_order_acquire);
if (oldCount >= 0 && m_sema.try_wait())
break;
if (oldCount < 0 && m_count.compare_exchange_strong(oldCount, oldCount + 1, std::memory_order_relaxed, std::memory_order_relaxed))
return 0;
}
}
}
if (max > 1)
return 1 + tryWaitMany(max - 1);
return 1;
}
public:
LightweightSemaphore(ssize_t initialCount = 0) : m_count(initialCount)
{
assert(initialCount >= 0);
}
bool tryWait()
{
ssize_t oldCount = m_count.load(std::memory_order_relaxed);
while (oldCount > 0)
{
if (m_count.compare_exchange_weak(oldCount, oldCount - 1, std::memory_order_acquire, std::memory_order_relaxed))
return true;
}
return false;
}
bool wait()
{
return tryWait() || waitWithPartialSpinning();
}
bool wait(std::int64_t timeout_usecs)
{
return tryWait() || waitWithPartialSpinning(timeout_usecs);
}
// Acquires between 0 and (greedily) max, inclusive
ssize_t tryWaitMany(ssize_t max)
{
assert(max >= 0);
ssize_t oldCount = m_count.load(std::memory_order_relaxed);
while (oldCount > 0)
{
ssize_t newCount = oldCount > max ? oldCount - max : 0;
if (m_count.compare_exchange_weak(oldCount, newCount, std::memory_order_acquire, std::memory_order_relaxed))
return oldCount - newCount;
}
return 0;
}
// Acquires at least one, and (greedily) at most max
ssize_t waitMany(ssize_t max, std::int64_t timeout_usecs)
{
assert(max >= 0);
ssize_t result = tryWaitMany(max);
if (result == 0 && max > 0)
result = waitManyWithPartialSpinning(max, timeout_usecs);
return result;
}
ssize_t waitMany(ssize_t max)
{
ssize_t result = waitMany(max, -1);
assert(result > 0);
return result;
}
void signal(ssize_t count = 1)
{
assert(count >= 0);
ssize_t oldCount = m_count.fetch_add(count, std::memory_order_release);
ssize_t toRelease = -oldCount < count ? -oldCount : count;
if (toRelease > 0)
{
m_sema.signal((int)toRelease);
}
}
ssize_t availableApprox() const
{
ssize_t count = m_count.load(std::memory_order_relaxed);
return count > 0 ? count : 0;
}
};
} // end namespace moodycamel