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111 lines
3.9 KiB
C++
111 lines
3.9 KiB
C++
/** Lock-free Multiple-Producer Multiple-consumer (MPMC) queue.
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*
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* Based on Dmitry Vyukov#s Bounded MPMC queue:
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* http://www.1024cores.net/home/lock-free-algorithms/queues/bounded-mpmc-queue
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*
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* @author Steffen Vogel <post@steffenvogel.de>
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* @copyright 2014-2020, Steffen Vogel
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* @license BSD 2-Clause License
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*
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modiffication, are permitted provided that the following conditions are met:
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*
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* * Redistributions of source code must retain the above copyright notice, this
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* list of conditions and the following disclaimer.
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*
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* * Redistributions in binary form must reproduce the above copyright notice,
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* this list of conditions and the following disclaimer in the documentation
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* and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
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* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*********************************************************************************/
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#pragma once
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#include <atomic>
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#include <cstddef>
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#include <cstdint>
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#include <unistd.h>
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#include <villas/common.hpp>
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#include <villas/config.h>
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#include <villas/memory_type.h>
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typedef char cacheline_pad_t[CACHELINE_SIZE];
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struct queue_cell {
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std::atomic<size_t> sequence;
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off_t data_off; /**< Pointer relative to the queue struct */
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};
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/** A lock-free multiple-producer, multiple-consumer (MPMC) queue. */
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struct queue {
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std::atomic<enum State> state;
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cacheline_pad_t _pad0; /**< Shared area: all threads read */
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size_t buffer_mask;
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off_t buffer_off; /**< Relative pointer to struct queue_cell[] */
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cacheline_pad_t _pad1; /**< Producer area: only producers read & write */
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std::atomic<size_t> tail; /**< Queue tail pointer */
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cacheline_pad_t _pad2; /**< Consumer area: only consumers read & write */
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std::atomic<size_t> head; /**< Queue head pointer */
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cacheline_pad_t _pad3; /**< @todo Why needed? */
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};
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/** Initialize MPMC queue */
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int queue_init(struct queue *q, size_t size, struct memory_type *mem = memory_default) __attribute__ ((warn_unused_result));
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/** Desroy MPMC queue and release memory */
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int queue_destroy(struct queue *q) __attribute__ ((warn_unused_result));
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/** Return estimation of current queue usage.
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*
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* Note: This is only an estimation and not accurate as long other
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* threads are performing operations.
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*/
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size_t queue_available(struct queue *q);
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int queue_push(struct queue *q, void *ptr);
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int queue_pull(struct queue *q, void **ptr);
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/** Enqueue up to \p cnt pointers of the \p ptr array into the queue.
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*
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* @return The number of pointers actually enqueued.
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* This number can be smaller then \p cnt in case the queue is filled.
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*/
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int queue_push_many(struct queue *q, void *ptr[], size_t cnt);
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/** Dequeue up to \p cnt pointers from the queue and place them into the \p ptr array.
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*
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* @return The number of pointers actually dequeued.
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* This number can be smaller than \p cnt in case the queue contained less than
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* \p cnt elements.
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*/
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int queue_pull_many(struct queue *q, void *ptr[], size_t cnt);
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/** Closes the queue, causing following writes to fail and following reads (after
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* the queue is empty) to fail.
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*
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* @return 0 on success.
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* @return -1 on failure.
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*/
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int queue_close(struct queue *q);
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