940 lines
36 KiB
C++
Executable file
940 lines
36 KiB
C++
Executable file
// SPDX-FileCopyrightText: 2013-2020 Cameron Desrochers
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// SPDX-License-Identifier: BSD-2-Clause
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#pragma once
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#include <cassert>
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#include <cstdint>
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#include <cstdlib> // For malloc/free/abort & size_t
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#include <memory>
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#include <new>
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#include <stdexcept>
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#include <type_traits>
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#include <utility>
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#include "common/atomic_helpers.h"
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#if __cplusplus > 199711L || _MSC_VER >= 1700 // C++11 or VS2012
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#include <chrono>
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#endif
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// A lock-free queue for a single-consumer, single-producer architecture.
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// The queue is also wait-free in the common path (except if more memory
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// needs to be allocated, in which case malloc is called).
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// Allocates memory sparingly, and only once if the original maximum size
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// estimate is never exceeded.
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// Tested on x86/x64 processors, but semantics should be correct for all
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// architectures (given the right implementations in atomicops.h), provided
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// that aligned integer and pointer accesses are naturally atomic.
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// Note that there should only be one consumer thread and producer thread;
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// Switching roles of the threads, or using multiple consecutive threads for
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// one role, is not safe unless properly synchronized.
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// Using the queue exclusively from one thread is fine, though a bit silly.
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#ifndef MOODYCAMEL_CACHE_LINE_SIZE
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#define MOODYCAMEL_CACHE_LINE_SIZE 64
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#endif
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#ifndef MOODYCAMEL_EXCEPTIONS_ENABLED
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#if (defined(_MSC_VER) && defined(_CPPUNWIND)) || (defined(__GNUC__) && defined(__EXCEPTIONS)) || \
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(!defined(_MSC_VER) && !defined(__GNUC__))
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#define MOODYCAMEL_EXCEPTIONS_ENABLED
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#endif
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#endif
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#ifndef MOODYCAMEL_HAS_EMPLACE
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#if !defined(_MSC_VER) || \
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_MSC_VER >= 1800 // variadic templates: either a non-MS compiler or VS >= 2013
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#define MOODYCAMEL_HAS_EMPLACE 1
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#endif
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#endif
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#ifndef MOODYCAMEL_MAYBE_ALIGN_TO_CACHELINE
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#if defined(__APPLE__) && defined(__MACH__) && __cplusplus >= 201703L
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// This is required to find out what deployment target we are using
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#include <CoreFoundation/CoreFoundation.h>
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#if !defined(MAC_OS_X_VERSION_MIN_REQUIRED) || \
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MAC_OS_X_VERSION_MIN_REQUIRED < MAC_OS_X_VERSION_10_14
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// C++17 new(size_t, align_val_t) is not backwards-compatible with older versions of macOS, so we
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// can't support over-alignment in this case
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#define MOODYCAMEL_MAYBE_ALIGN_TO_CACHELINE
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#endif
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#endif
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#endif
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#ifndef MOODYCAMEL_MAYBE_ALIGN_TO_CACHELINE
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#define MOODYCAMEL_MAYBE_ALIGN_TO_CACHELINE AE_ALIGN(MOODYCAMEL_CACHE_LINE_SIZE)
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#endif
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#ifdef AE_VCPP
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#pragma warning(push)
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#pragma warning(disable : 4324) // structure was padded due to __declspec(align())
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#pragma warning(disable : 4820) // padding was added
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#pragma warning(disable : 4127) // conditional expression is constant
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#endif
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namespace Common {
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template <typename T, size_t MAX_BLOCK_SIZE = 512>
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class MOODYCAMEL_MAYBE_ALIGN_TO_CACHELINE ReaderWriterQueue {
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// Design: Based on a queue-of-queues. The low-level queues are just
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// circular buffers with front and tail indices indicating where the
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// next element to dequeue is and where the next element can be enqueued,
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// respectively. Each low-level queue is called a "block". Each block
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// wastes exactly one element's worth of space to keep the design simple
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// (if front == tail then the queue is empty, and can't be full).
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// The high-level queue is a circular linked list of blocks; again there
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// is a front and tail, but this time they are pointers to the blocks.
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// The front block is where the next element to be dequeued is, provided
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// the block is not empty. The back block is where elements are to be
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// enqueued, provided the block is not full.
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// The producer thread owns all the tail indices/pointers. The consumer
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// thread owns all the front indices/pointers. Both threads read each
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// other's variables, but only the owning thread updates them. E.g. After
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// the consumer reads the producer's tail, the tail may change before the
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// consumer is done dequeuing an object, but the consumer knows the tail
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// will never go backwards, only forwards.
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// If there is no room to enqueue an object, an additional block (of
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// equal size to the last block) is added. Blocks are never removed.
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public:
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typedef T value_type;
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// Constructs a queue that can hold at least `size` elements without further
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// allocations. If more than MAX_BLOCK_SIZE elements are requested,
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// then several blocks of MAX_BLOCK_SIZE each are reserved (including
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// at least one extra buffer block).
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AE_NO_TSAN explicit ReaderWriterQueue(size_t size = 15)
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#ifndef NDEBUG
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: enqueuing(false), dequeuing(false)
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#endif
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{
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assert(MAX_BLOCK_SIZE == ceilToPow2(MAX_BLOCK_SIZE) &&
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"MAX_BLOCK_SIZE must be a power of 2");
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assert(MAX_BLOCK_SIZE >= 2 && "MAX_BLOCK_SIZE must be at least 2");
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Block* firstBlock = nullptr;
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largestBlockSize =
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ceilToPow2(size + 1); // We need a spare slot to fit size elements in the block
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if (largestBlockSize > MAX_BLOCK_SIZE * 2) {
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// We need a spare block in case the producer is writing to a different block the
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// consumer is reading from, and wants to enqueue the maximum number of elements. We
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// also need a spare element in each block to avoid the ambiguity between front == tail
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// meaning "empty" and "full". So the effective number of slots that are guaranteed to
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// be usable at any time is the block size - 1 times the number of blocks - 1. Solving
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// for size and applying a ceiling to the division gives us (after simplifying):
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size_t initialBlockCount = (size + MAX_BLOCK_SIZE * 2 - 3) / (MAX_BLOCK_SIZE - 1);
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largestBlockSize = MAX_BLOCK_SIZE;
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Block* lastBlock = nullptr;
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for (size_t i = 0; i != initialBlockCount; ++i) {
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auto block = make_block(largestBlockSize);
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if (block == nullptr) {
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#ifdef MOODYCAMEL_EXCEPTIONS_ENABLED
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throw std::bad_alloc();
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#else
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abort();
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#endif
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}
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if (firstBlock == nullptr) {
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firstBlock = block;
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} else {
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lastBlock->next = block;
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}
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lastBlock = block;
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block->next = firstBlock;
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}
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} else {
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firstBlock = make_block(largestBlockSize);
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if (firstBlock == nullptr) {
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#ifdef MOODYCAMEL_EXCEPTIONS_ENABLED
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throw std::bad_alloc();
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#else
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abort();
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#endif
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}
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firstBlock->next = firstBlock;
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}
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frontBlock = firstBlock;
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tailBlock = firstBlock;
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// Make sure the reader/writer threads will have the initialized memory setup above:
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fence(memory_order_sync);
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}
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// Note: The queue should not be accessed concurrently while it's
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// being moved. It's up to the user to synchronize this.
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AE_NO_TSAN ReaderWriterQueue(ReaderWriterQueue&& other)
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: frontBlock(other.frontBlock.load()), tailBlock(other.tailBlock.load()),
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largestBlockSize(other.largestBlockSize)
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#ifndef NDEBUG
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,
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enqueuing(false), dequeuing(false)
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#endif
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{
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other.largestBlockSize = 32;
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Block* b = other.make_block(other.largestBlockSize);
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if (b == nullptr) {
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#ifdef MOODYCAMEL_EXCEPTIONS_ENABLED
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throw std::bad_alloc();
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#else
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abort();
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#endif
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}
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b->next = b;
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other.frontBlock = b;
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other.tailBlock = b;
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}
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// Note: The queue should not be accessed concurrently while it's
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// being moved. It's up to the user to synchronize this.
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ReaderWriterQueue& operator=(ReaderWriterQueue&& other) AE_NO_TSAN {
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Block* b = frontBlock.load();
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frontBlock = other.frontBlock.load();
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other.frontBlock = b;
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b = tailBlock.load();
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tailBlock = other.tailBlock.load();
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other.tailBlock = b;
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std::swap(largestBlockSize, other.largestBlockSize);
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return *this;
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}
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// Note: The queue should not be accessed concurrently while it's
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// being deleted. It's up to the user to synchronize this.
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AE_NO_TSAN ~ReaderWriterQueue() {
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// Make sure we get the latest version of all variables from other CPUs:
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fence(memory_order_sync);
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// Destroy any remaining objects in queue and free memory
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Block* frontBlock_ = frontBlock;
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Block* block = frontBlock_;
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do {
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Block* nextBlock = block->next;
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size_t blockFront = block->front;
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size_t blockTail = block->tail;
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for (size_t i = blockFront; i != blockTail; i = (i + 1) & block->sizeMask) {
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auto element = reinterpret_cast<T*>(block->data + i * sizeof(T));
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element->~T();
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(void)element;
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}
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auto rawBlock = block->rawThis;
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block->~Block();
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std::free(rawBlock);
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block = nextBlock;
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} while (block != frontBlock_);
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}
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// Enqueues a copy of element if there is room in the queue.
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// Returns true if the element was enqueued, false otherwise.
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// Does not allocate memory.
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AE_FORCEINLINE bool try_enqueue(T const& element) AE_NO_TSAN {
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return inner_enqueue<CannotAlloc>(element);
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}
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// Enqueues a moved copy of element if there is room in the queue.
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// Returns true if the element was enqueued, false otherwise.
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// Does not allocate memory.
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AE_FORCEINLINE bool try_enqueue(T&& element) AE_NO_TSAN {
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return inner_enqueue<CannotAlloc>(std::forward<T>(element));
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}
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#if MOODYCAMEL_HAS_EMPLACE
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// Like try_enqueue() but with emplace semantics (i.e. construct-in-place).
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template <typename... Args>
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AE_FORCEINLINE bool try_emplace(Args&&... args) AE_NO_TSAN {
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return inner_enqueue<CannotAlloc>(std::forward<Args>(args)...);
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}
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#endif
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// Enqueues a copy of element on the queue.
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// Allocates an additional block of memory if needed.
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// Only fails (returns false) if memory allocation fails.
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AE_FORCEINLINE bool enqueue(T const& element) AE_NO_TSAN {
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return inner_enqueue<CanAlloc>(element);
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}
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// Enqueues a moved copy of element on the queue.
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// Allocates an additional block of memory if needed.
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// Only fails (returns false) if memory allocation fails.
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AE_FORCEINLINE bool enqueue(T&& element) AE_NO_TSAN {
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return inner_enqueue<CanAlloc>(std::forward<T>(element));
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}
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#if MOODYCAMEL_HAS_EMPLACE
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// Like enqueue() but with emplace semantics (i.e. construct-in-place).
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template <typename... Args>
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AE_FORCEINLINE bool emplace(Args&&... args) AE_NO_TSAN {
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return inner_enqueue<CanAlloc>(std::forward<Args>(args)...);
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}
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#endif
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// Attempts to dequeue an element; if the queue is empty,
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// returns false instead. If the queue has at least one element,
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// moves front to result using operator=, then returns true.
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template <typename U>
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bool try_dequeue(U& result) AE_NO_TSAN {
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#ifndef NDEBUG
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ReentrantGuard guard(this->dequeuing);
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#endif
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// High-level pseudocode:
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// Remember where the tail block is
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// If the front block has an element in it, dequeue it
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// Else
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// If front block was the tail block when we entered the function, return false
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// Else advance to next block and dequeue the item there
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// Note that we have to use the value of the tail block from before we check if the front
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// block is full or not, in case the front block is empty and then, before we check if the
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// tail block is at the front block or not, the producer fills up the front block *and
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// moves on*, which would make us skip a filled block. Seems unlikely, but was consistently
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// reproducible in practice.
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// In order to avoid overhead in the common case, though, we do a double-checked pattern
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// where we have the fast path if the front block is not empty, then read the tail block,
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// then re-read the front block and check if it's not empty again, then check if the tail
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// block has advanced.
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Block* frontBlock_ = frontBlock.load();
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size_t blockTail = frontBlock_->localTail;
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size_t blockFront = frontBlock_->front.load();
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if (blockFront != blockTail ||
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blockFront != (frontBlock_->localTail = frontBlock_->tail.load())) {
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fence(memory_order_acquire);
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non_empty_front_block:
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// Front block not empty, dequeue from here
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auto element = reinterpret_cast<T*>(frontBlock_->data + blockFront * sizeof(T));
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result = std::move(*element);
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element->~T();
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blockFront = (blockFront + 1) & frontBlock_->sizeMask;
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fence(memory_order_release);
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frontBlock_->front = blockFront;
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} else if (frontBlock_ != tailBlock.load()) {
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fence(memory_order_acquire);
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frontBlock_ = frontBlock.load();
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blockTail = frontBlock_->localTail = frontBlock_->tail.load();
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blockFront = frontBlock_->front.load();
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fence(memory_order_acquire);
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if (blockFront != blockTail) {
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// Oh look, the front block isn't empty after all
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goto non_empty_front_block;
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}
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// Front block is empty but there's another block ahead, advance to it
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Block* nextBlock = frontBlock_->next;
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// Don't need an acquire fence here since next can only ever be set on the tailBlock,
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// and we're not the tailBlock, and we did an acquire earlier after reading tailBlock
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// which ensures next is up-to-date on this CPU in case we recently were at tailBlock.
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size_t nextBlockFront = nextBlock->front.load();
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size_t nextBlockTail = nextBlock->localTail = nextBlock->tail.load();
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fence(memory_order_acquire);
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// Since the tailBlock is only ever advanced after being written to,
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// we know there's for sure an element to dequeue on it
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assert(nextBlockFront != nextBlockTail);
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AE_UNUSED(nextBlockTail);
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// We're done with this block, let the producer use it if it needs
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fence(memory_order_release); // Expose possibly pending changes to frontBlock->front
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// from last dequeue
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frontBlock = frontBlock_ = nextBlock;
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compiler_fence(memory_order_release); // Not strictly needed
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auto element = reinterpret_cast<T*>(frontBlock_->data + nextBlockFront * sizeof(T));
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result = std::move(*element);
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element->~T();
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nextBlockFront = (nextBlockFront + 1) & frontBlock_->sizeMask;
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fence(memory_order_release);
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frontBlock_->front = nextBlockFront;
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} else {
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// No elements in current block and no other block to advance to
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return false;
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}
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return true;
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}
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// Returns a pointer to the front element in the queue (the one that
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// would be removed next by a call to `try_dequeue` or `pop`). If the
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// queue appears empty at the time the method is called, nullptr is
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// returned instead.
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// Must be called only from the consumer thread.
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T* peek() const AE_NO_TSAN {
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#ifndef NDEBUG
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ReentrantGuard guard(this->dequeuing);
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#endif
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// See try_dequeue() for reasoning
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Block* frontBlock_ = frontBlock.load();
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size_t blockTail = frontBlock_->localTail;
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size_t blockFront = frontBlock_->front.load();
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if (blockFront != blockTail ||
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blockFront != (frontBlock_->localTail = frontBlock_->tail.load())) {
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fence(memory_order_acquire);
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non_empty_front_block:
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return reinterpret_cast<T*>(frontBlock_->data + blockFront * sizeof(T));
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} else if (frontBlock_ != tailBlock.load()) {
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fence(memory_order_acquire);
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frontBlock_ = frontBlock.load();
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blockTail = frontBlock_->localTail = frontBlock_->tail.load();
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blockFront = frontBlock_->front.load();
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fence(memory_order_acquire);
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if (blockFront != blockTail) {
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goto non_empty_front_block;
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}
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Block* nextBlock = frontBlock_->next;
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size_t nextBlockFront = nextBlock->front.load();
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fence(memory_order_acquire);
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assert(nextBlockFront != nextBlock->tail.load());
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return reinterpret_cast<T*>(nextBlock->data + nextBlockFront * sizeof(T));
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}
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return nullptr;
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}
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// Removes the front element from the queue, if any, without returning it.
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// Returns true on success, or false if the queue appeared empty at the time
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// `pop` was called.
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bool pop() AE_NO_TSAN {
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#ifndef NDEBUG
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ReentrantGuard guard(this->dequeuing);
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#endif
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// See try_dequeue() for reasoning
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Block* frontBlock_ = frontBlock.load();
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size_t blockTail = frontBlock_->localTail;
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size_t blockFront = frontBlock_->front.load();
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if (blockFront != blockTail ||
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blockFront != (frontBlock_->localTail = frontBlock_->tail.load())) {
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fence(memory_order_acquire);
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non_empty_front_block:
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auto element = reinterpret_cast<T*>(frontBlock_->data + blockFront * sizeof(T));
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element->~T();
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blockFront = (blockFront + 1) & frontBlock_->sizeMask;
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fence(memory_order_release);
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frontBlock_->front = blockFront;
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} else if (frontBlock_ != tailBlock.load()) {
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fence(memory_order_acquire);
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frontBlock_ = frontBlock.load();
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blockTail = frontBlock_->localTail = frontBlock_->tail.load();
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blockFront = frontBlock_->front.load();
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fence(memory_order_acquire);
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if (blockFront != blockTail) {
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goto non_empty_front_block;
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}
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// Front block is empty but there's another block ahead, advance to it
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Block* nextBlock = frontBlock_->next;
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size_t nextBlockFront = nextBlock->front.load();
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size_t nextBlockTail = nextBlock->localTail = nextBlock->tail.load();
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fence(memory_order_acquire);
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assert(nextBlockFront != nextBlockTail);
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AE_UNUSED(nextBlockTail);
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fence(memory_order_release);
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frontBlock = frontBlock_ = nextBlock;
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compiler_fence(memory_order_release);
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auto element = reinterpret_cast<T*>(frontBlock_->data + nextBlockFront * sizeof(T));
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element->~T();
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nextBlockFront = (nextBlockFront + 1) & frontBlock_->sizeMask;
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fence(memory_order_release);
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frontBlock_->front = nextBlockFront;
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} else {
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// No elements in current block and no other block to advance to
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return false;
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}
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return true;
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}
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// Returns the approximate number of items currently in the queue.
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// Safe to call from both the producer and consumer threads.
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inline size_t size_approx() const AE_NO_TSAN {
|
|
size_t result = 0;
|
|
Block* frontBlock_ = frontBlock.load();
|
|
Block* block = frontBlock_;
|
|
do {
|
|
fence(memory_order_acquire);
|
|
size_t blockFront = block->front.load();
|
|
size_t blockTail = block->tail.load();
|
|
result += (blockTail - blockFront) & block->sizeMask;
|
|
block = block->next.load();
|
|
} while (block != frontBlock_);
|
|
return result;
|
|
}
|
|
|
|
// Returns the total number of items that could be enqueued without incurring
|
|
// an allocation when this queue is empty.
|
|
// Safe to call from both the producer and consumer threads.
|
|
//
|
|
// NOTE: The actual capacity during usage may be different depending on the consumer.
|
|
// If the consumer is removing elements concurrently, the producer cannot add to
|
|
// the block the consumer is removing from until it's completely empty, except in
|
|
// the case where the producer was writing to the same block the consumer was
|
|
// reading from the whole time.
|
|
inline size_t max_capacity() const {
|
|
size_t result = 0;
|
|
Block* frontBlock_ = frontBlock.load();
|
|
Block* block = frontBlock_;
|
|
do {
|
|
fence(memory_order_acquire);
|
|
result += block->sizeMask;
|
|
block = block->next.load();
|
|
} while (block != frontBlock_);
|
|
return result;
|
|
}
|
|
|
|
private:
|
|
enum AllocationMode { CanAlloc, CannotAlloc };
|
|
|
|
#if MOODYCAMEL_HAS_EMPLACE
|
|
template <AllocationMode canAlloc, typename... Args>
|
|
bool inner_enqueue(Args&&... args) AE_NO_TSAN
|
|
#else
|
|
template <AllocationMode canAlloc, typename U>
|
|
bool inner_enqueue(U&& element) AE_NO_TSAN
|
|
#endif
|
|
{
|
|
#ifndef NDEBUG
|
|
ReentrantGuard guard(this->enqueuing);
|
|
#endif
|
|
|
|
// High-level pseudocode (assuming we're allowed to alloc a new block):
|
|
// If room in tail block, add to tail
|
|
// Else check next block
|
|
// If next block is not the head block, enqueue on next block
|
|
// Else create a new block and enqueue there
|
|
// Advance tail to the block we just enqueued to
|
|
|
|
Block* tailBlock_ = tailBlock.load();
|
|
size_t blockFront = tailBlock_->localFront;
|
|
size_t blockTail = tailBlock_->tail.load();
|
|
|
|
size_t nextBlockTail = (blockTail + 1) & tailBlock_->sizeMask;
|
|
if (nextBlockTail != blockFront ||
|
|
nextBlockTail != (tailBlock_->localFront = tailBlock_->front.load())) {
|
|
fence(memory_order_acquire);
|
|
// This block has room for at least one more element
|
|
char* location = tailBlock_->data + blockTail * sizeof(T);
|
|
#if MOODYCAMEL_HAS_EMPLACE
|
|
new (location) T(std::forward<Args>(args)...);
|
|
#else
|
|
new (location) T(std::forward<U>(element));
|
|
#endif
|
|
|
|
fence(memory_order_release);
|
|
tailBlock_->tail = nextBlockTail;
|
|
} else {
|
|
fence(memory_order_acquire);
|
|
if (tailBlock_->next.load() != frontBlock) {
|
|
// Note that the reason we can't advance to the frontBlock and start adding new
|
|
// entries there is because if we did, then dequeue would stay in that block,
|
|
// eventually reading the new values, instead of advancing to the next full block
|
|
// (whose values were enqueued first and so should be consumed first).
|
|
|
|
fence(memory_order_acquire); // Ensure we get latest writes if we got the latest
|
|
// frontBlock
|
|
|
|
// tailBlock is full, but there's a free block ahead, use it
|
|
Block* tailBlockNext = tailBlock_->next.load();
|
|
size_t nextBlockFront = tailBlockNext->localFront = tailBlockNext->front.load();
|
|
nextBlockTail = tailBlockNext->tail.load();
|
|
fence(memory_order_acquire);
|
|
|
|
// This block must be empty since it's not the head block and we
|
|
// go through the blocks in a circle
|
|
assert(nextBlockFront == nextBlockTail);
|
|
tailBlockNext->localFront = nextBlockFront;
|
|
|
|
char* location = tailBlockNext->data + nextBlockTail * sizeof(T);
|
|
#if MOODYCAMEL_HAS_EMPLACE
|
|
new (location) T(std::forward<Args>(args)...);
|
|
#else
|
|
new (location) T(std::forward<U>(element));
|
|
#endif
|
|
|
|
tailBlockNext->tail = (nextBlockTail + 1) & tailBlockNext->sizeMask;
|
|
|
|
fence(memory_order_release);
|
|
tailBlock = tailBlockNext;
|
|
} else if (canAlloc == CanAlloc) {
|
|
// tailBlock is full and there's no free block ahead; create a new block
|
|
auto newBlockSize =
|
|
largestBlockSize >= MAX_BLOCK_SIZE ? largestBlockSize : largestBlockSize * 2;
|
|
auto newBlock = make_block(newBlockSize);
|
|
if (newBlock == nullptr) {
|
|
// Could not allocate a block!
|
|
return false;
|
|
}
|
|
largestBlockSize = newBlockSize;
|
|
|
|
#if MOODYCAMEL_HAS_EMPLACE
|
|
new (newBlock->data) T(std::forward<Args>(args)...);
|
|
#else
|
|
new (newBlock->data) T(std::forward<U>(element));
|
|
#endif
|
|
assert(newBlock->front == 0);
|
|
newBlock->tail = newBlock->localTail = 1;
|
|
|
|
newBlock->next = tailBlock_->next.load();
|
|
tailBlock_->next = newBlock;
|
|
|
|
// Might be possible for the dequeue thread to see the new tailBlock->next
|
|
// *without* seeing the new tailBlock value, but this is OK since it can't
|
|
// advance to the next block until tailBlock is set anyway (because the only
|
|
// case where it could try to read the next is if it's already at the tailBlock,
|
|
// and it won't advance past tailBlock in any circumstance).
|
|
|
|
fence(memory_order_release);
|
|
tailBlock = newBlock;
|
|
} else if (canAlloc == CannotAlloc) {
|
|
// Would have had to allocate a new block to enqueue, but not allowed
|
|
return false;
|
|
} else {
|
|
assert(false && "Should be unreachable code");
|
|
return false;
|
|
}
|
|
}
|
|
|
|
return true;
|
|
}
|
|
|
|
// Disable copying
|
|
ReaderWriterQueue(ReaderWriterQueue const&) {}
|
|
|
|
// Disable assignment
|
|
ReaderWriterQueue& operator=(ReaderWriterQueue const&) {}
|
|
|
|
AE_FORCEINLINE static size_t ceilToPow2(size_t x) {
|
|
// From http://graphics.stanford.edu/~seander/bithacks.html#RoundUpPowerOf2
|
|
--x;
|
|
x |= x >> 1;
|
|
x |= x >> 2;
|
|
x |= x >> 4;
|
|
for (size_t i = 1; i < sizeof(size_t); i <<= 1) {
|
|
x |= x >> (i << 3);
|
|
}
|
|
++x;
|
|
return x;
|
|
}
|
|
|
|
template <typename U>
|
|
static AE_FORCEINLINE char* align_for(char* ptr) AE_NO_TSAN {
|
|
const std::size_t alignment = std::alignment_of<U>::value;
|
|
return ptr + (alignment - (reinterpret_cast<std::uintptr_t>(ptr) % alignment)) % alignment;
|
|
}
|
|
|
|
private:
|
|
#ifndef NDEBUG
|
|
struct ReentrantGuard {
|
|
AE_NO_TSAN ReentrantGuard(weak_atomic<bool>& _inSection) : inSection(_inSection) {
|
|
assert(!inSection &&
|
|
"Concurrent (or re-entrant) enqueue or dequeue operation detected (only one "
|
|
"thread at a time may hold the producer or consumer role)");
|
|
inSection = true;
|
|
}
|
|
|
|
AE_NO_TSAN ~ReentrantGuard() {
|
|
inSection = false;
|
|
}
|
|
|
|
private:
|
|
ReentrantGuard& operator=(ReentrantGuard const&);
|
|
|
|
private:
|
|
weak_atomic<bool>& inSection;
|
|
};
|
|
#endif
|
|
|
|
struct Block {
|
|
// Avoid false-sharing by putting highly contended variables on their own cache lines
|
|
weak_atomic<size_t> front; // (Atomic) Elements are read from here
|
|
size_t localTail; // An uncontended shadow copy of tail, owned by the consumer
|
|
|
|
char cachelineFiller0[MOODYCAMEL_CACHE_LINE_SIZE - sizeof(weak_atomic<size_t>) -
|
|
sizeof(size_t)];
|
|
weak_atomic<size_t> tail; // (Atomic) Elements are enqueued here
|
|
size_t localFront;
|
|
|
|
char cachelineFiller1[MOODYCAMEL_CACHE_LINE_SIZE - sizeof(weak_atomic<size_t>) -
|
|
sizeof(size_t)]; // next isn't very contended, but we don't want it on
|
|
// the same cache line as tail (which is)
|
|
weak_atomic<Block*> next; // (Atomic)
|
|
|
|
char* data; // Contents (on heap) are aligned to T's alignment
|
|
|
|
const size_t sizeMask;
|
|
|
|
// size must be a power of two (and greater than 0)
|
|
AE_NO_TSAN Block(size_t const& _size, char* _rawThis, char* _data)
|
|
: front(0UL), localTail(0), tail(0UL), localFront(0), next(nullptr), data(_data),
|
|
sizeMask(_size - 1), rawThis(_rawThis) {}
|
|
|
|
private:
|
|
// C4512 - Assignment operator could not be generated
|
|
Block& operator=(Block const&);
|
|
|
|
public:
|
|
char* rawThis;
|
|
};
|
|
|
|
static Block* make_block(size_t capacity) AE_NO_TSAN {
|
|
// Allocate enough memory for the block itself, as well as all the elements it will contain
|
|
auto size = sizeof(Block) + std::alignment_of<Block>::value - 1;
|
|
size += sizeof(T) * capacity + std::alignment_of<T>::value - 1;
|
|
auto newBlockRaw = static_cast<char*>(std::malloc(size));
|
|
if (newBlockRaw == nullptr) {
|
|
return nullptr;
|
|
}
|
|
|
|
auto newBlockAligned = align_for<Block>(newBlockRaw);
|
|
auto newBlockData = align_for<T>(newBlockAligned + sizeof(Block));
|
|
return new (newBlockAligned) Block(capacity, newBlockRaw, newBlockData);
|
|
}
|
|
|
|
private:
|
|
weak_atomic<Block*> frontBlock; // (Atomic) Elements are dequeued from this block
|
|
|
|
char cachelineFiller[MOODYCAMEL_CACHE_LINE_SIZE - sizeof(weak_atomic<Block*>)];
|
|
weak_atomic<Block*> tailBlock; // (Atomic) Elements are enqueued to this block
|
|
|
|
size_t largestBlockSize;
|
|
|
|
#ifndef NDEBUG
|
|
weak_atomic<bool> enqueuing;
|
|
mutable weak_atomic<bool> dequeuing;
|
|
#endif
|
|
};
|
|
|
|
// Like ReaderWriterQueue, but also providees blocking operations
|
|
template <typename T, size_t MAX_BLOCK_SIZE = 512>
|
|
class BlockingReaderWriterQueue {
|
|
private:
|
|
typedef ::Common::ReaderWriterQueue<T, MAX_BLOCK_SIZE> ReaderWriterQueue;
|
|
|
|
public:
|
|
explicit BlockingReaderWriterQueue(size_t size = 15) AE_NO_TSAN
|
|
: inner(size),
|
|
sema(new spsc_sema::LightweightSemaphore()) {}
|
|
|
|
BlockingReaderWriterQueue(BlockingReaderWriterQueue&& other) AE_NO_TSAN
|
|
: inner(std::move(other.inner)),
|
|
sema(std::move(other.sema)) {}
|
|
|
|
BlockingReaderWriterQueue& operator=(BlockingReaderWriterQueue&& other) AE_NO_TSAN {
|
|
std::swap(sema, other.sema);
|
|
std::swap(inner, other.inner);
|
|
return *this;
|
|
}
|
|
|
|
// Enqueues a copy of element if there is room in the queue.
|
|
// Returns true if the element was enqueued, false otherwise.
|
|
// Does not allocate memory.
|
|
AE_FORCEINLINE bool try_enqueue(T const& element) AE_NO_TSAN {
|
|
if (inner.try_enqueue(element)) {
|
|
sema->signal();
|
|
return true;
|
|
}
|
|
return false;
|
|
}
|
|
|
|
// Enqueues a moved copy of element if there is room in the queue.
|
|
// Returns true if the element was enqueued, false otherwise.
|
|
// Does not allocate memory.
|
|
AE_FORCEINLINE bool try_enqueue(T&& element) AE_NO_TSAN {
|
|
if (inner.try_enqueue(std::forward<T>(element))) {
|
|
sema->signal();
|
|
return true;
|
|
}
|
|
return false;
|
|
}
|
|
|
|
#if MOODYCAMEL_HAS_EMPLACE
|
|
// Like try_enqueue() but with emplace semantics (i.e. construct-in-place).
|
|
template <typename... Args>
|
|
AE_FORCEINLINE bool try_emplace(Args&&... args) AE_NO_TSAN {
|
|
if (inner.try_emplace(std::forward<Args>(args)...)) {
|
|
sema->signal();
|
|
return true;
|
|
}
|
|
return false;
|
|
}
|
|
#endif
|
|
|
|
// Enqueues a copy of element on the queue.
|
|
// Allocates an additional block of memory if needed.
|
|
// Only fails (returns false) if memory allocation fails.
|
|
AE_FORCEINLINE bool enqueue(T const& element) AE_NO_TSAN {
|
|
if (inner.enqueue(element)) {
|
|
sema->signal();
|
|
return true;
|
|
}
|
|
return false;
|
|
}
|
|
|
|
// Enqueues a moved copy of element on the queue.
|
|
// Allocates an additional block of memory if needed.
|
|
// Only fails (returns false) if memory allocation fails.
|
|
AE_FORCEINLINE bool enqueue(T&& element) AE_NO_TSAN {
|
|
if (inner.enqueue(std::forward<T>(element))) {
|
|
sema->signal();
|
|
return true;
|
|
}
|
|
return false;
|
|
}
|
|
|
|
#if MOODYCAMEL_HAS_EMPLACE
|
|
// Like enqueue() but with emplace semantics (i.e. construct-in-place).
|
|
template <typename... Args>
|
|
AE_FORCEINLINE bool emplace(Args&&... args) AE_NO_TSAN {
|
|
if (inner.emplace(std::forward<Args>(args)...)) {
|
|
sema->signal();
|
|
return true;
|
|
}
|
|
return false;
|
|
}
|
|
#endif
|
|
|
|
// Attempts to dequeue an element; if the queue is empty,
|
|
// returns false instead. If the queue has at least one element,
|
|
// moves front to result using operator=, then returns true.
|
|
template <typename U>
|
|
bool try_dequeue(U& result) AE_NO_TSAN {
|
|
if (sema->tryWait()) {
|
|
bool success = inner.try_dequeue(result);
|
|
assert(success);
|
|
AE_UNUSED(success);
|
|
return true;
|
|
}
|
|
return false;
|
|
}
|
|
|
|
// Attempts to dequeue an element; if the queue is empty,
|
|
// waits until an element is available, then dequeues it.
|
|
template <typename U>
|
|
void wait_dequeue(U& result) AE_NO_TSAN {
|
|
while (!sema->wait())
|
|
;
|
|
bool success = inner.try_dequeue(result);
|
|
AE_UNUSED(result);
|
|
assert(success);
|
|
AE_UNUSED(success);
|
|
}
|
|
|
|
// Attempts to dequeue an element; if the queue is empty,
|
|
// waits until an element is available up to the specified timeout,
|
|
// then dequeues it and returns true, or returns false if the timeout
|
|
// expires before an element can be dequeued.
|
|
// Using a negative timeout indicates an indefinite timeout,
|
|
// and is thus functionally equivalent to calling wait_dequeue.
|
|
template <typename U>
|
|
bool wait_dequeue_timed(U& result, std::int64_t timeout_usecs) AE_NO_TSAN {
|
|
if (!sema->wait(timeout_usecs)) {
|
|
return false;
|
|
}
|
|
bool success = inner.try_dequeue(result);
|
|
AE_UNUSED(result);
|
|
assert(success);
|
|
AE_UNUSED(success);
|
|
return true;
|
|
}
|
|
|
|
#if __cplusplus > 199711L || _MSC_VER >= 1700
|
|
// Attempts to dequeue an element; if the queue is empty,
|
|
// waits until an element is available up to the specified timeout,
|
|
// then dequeues it and returns true, or returns false if the timeout
|
|
// expires before an element can be dequeued.
|
|
// Using a negative timeout indicates an indefinite timeout,
|
|
// and is thus functionally equivalent to calling wait_dequeue.
|
|
template <typename U, typename Rep, typename Period>
|
|
inline bool wait_dequeue_timed(U& result,
|
|
std::chrono::duration<Rep, Period> const& timeout) AE_NO_TSAN {
|
|
return wait_dequeue_timed(
|
|
result, std::chrono::duration_cast<std::chrono::microseconds>(timeout).count());
|
|
}
|
|
#endif
|
|
|
|
// Returns a pointer to the front element in the queue (the one that
|
|
// would be removed next by a call to `try_dequeue` or `pop`). If the
|
|
// queue appears empty at the time the method is called, nullptr is
|
|
// returned instead.
|
|
// Must be called only from the consumer thread.
|
|
AE_FORCEINLINE T* peek() const AE_NO_TSAN {
|
|
return inner.peek();
|
|
}
|
|
|
|
// Removes the front element from the queue, if any, without returning it.
|
|
// Returns true on success, or false if the queue appeared empty at the time
|
|
// `pop` was called.
|
|
AE_FORCEINLINE bool pop() AE_NO_TSAN {
|
|
if (sema->tryWait()) {
|
|
bool result = inner.pop();
|
|
assert(result);
|
|
AE_UNUSED(result);
|
|
return true;
|
|
}
|
|
return false;
|
|
}
|
|
|
|
// Returns the approximate number of items currently in the queue.
|
|
// Safe to call from both the producer and consumer threads.
|
|
AE_FORCEINLINE size_t size_approx() const AE_NO_TSAN {
|
|
return sema->availableApprox();
|
|
}
|
|
|
|
// Returns the total number of items that could be enqueued without incurring
|
|
// an allocation when this queue is empty.
|
|
// Safe to call from both the producer and consumer threads.
|
|
//
|
|
// NOTE: The actual capacity during usage may be different depending on the consumer.
|
|
// If the consumer is removing elements concurrently, the producer cannot add to
|
|
// the block the consumer is removing from until it's completely empty, except in
|
|
// the case where the producer was writing to the same block the consumer was
|
|
// reading from the whole time.
|
|
AE_FORCEINLINE size_t max_capacity() const {
|
|
return inner.max_capacity();
|
|
}
|
|
|
|
private:
|
|
// Disable copying & assignment
|
|
BlockingReaderWriterQueue(BlockingReaderWriterQueue const&) {}
|
|
BlockingReaderWriterQueue& operator=(BlockingReaderWriterQueue const&) {}
|
|
|
|
private:
|
|
ReaderWriterQueue inner;
|
|
std::unique_ptr<spsc_sema::LightweightSemaphore> sema;
|
|
};
|
|
|
|
} // namespace Common
|
|
|
|
#ifdef AE_VCPP
|
|
#pragma warning(pop)
|
|
#endif
|