/** Lock-free Multiple-Producer Multiple-consumer (MPMC) queue. * * Based on Dmitry Vyukov#s Bounded MPMC queue: * http://www.1024cores.net/home/lock-free-algorithms/queues/bounded-mpmc-queue * * @author Steffen Vogel * @copyright 2017 Steffen Vogel * @license BSD 2-Clause License * * All rights reserved. * * Redistribution and use in source and binary forms, with or without * modiffication, are permitted provided that the following conditions are met: * * * Redistributions of source code must retain the above copyright notice, this * list of conditions and the following disclaimer. * * * Redistributions in binary form must reproduce the above copyright notice, * this list of conditions and the following disclaimer in the documentation * and/or other materials provided with the distribution. * * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. *********************************************************************************/ #pragma once #include #include #include #include "atomic.h" #include "common.h" /* Forward declarations */ struct memtype; #define CACHELINE_SIZE 64 typedef char cacheline_pad_t[CACHELINE_SIZE]; struct queue_cell { atomic_size_t sequence; off_t data_off; /**< Pointer relative to the queue struct */ }; /** A lock-free multiple-producer, multiple-consumer (MPMC) queue. */ struct queue { cacheline_pad_t _pad0; /**< Shared area: all threads read */ atomic_state state; struct memtype *mem; size_t buffer_mask; off_t buffer_off; /**< Relative pointer to struct queue_cell[] */ cacheline_pad_t _pad1; /**< Producer area: only producers read & write */ atomic_size_t tail; /**< Queue tail pointer */ cacheline_pad_t _pad2; /**< Consumer area: only consumers read & write */ atomic_size_t head; /**< Queue head pointer */ cacheline_pad_t _pad3; /**< @todo Why needed? */ }; /** Initialize MPMC queue */ int queue_init(struct queue *q, size_t size, struct memtype *mem); /** Desroy MPMC queue and release memory */ int queue_destroy(struct queue *q); /** Return estimation of current queue usage. * * Note: This is only an estimation and not accurate as long other * threads are performing operations. */ size_t queue_available(struct queue *q); int queue_push(struct queue *q, void *ptr); int queue_pull(struct queue *q, void **ptr); /** Enqueue up to \p cnt pointers of the \p ptr array into the queue. * * @return The number of pointers actually enqueued. * This number can be smaller then \p cnt in case the queue is filled. */ int queue_push_many(struct queue *q, void *ptr[], size_t cnt); /** Dequeue up to \p cnt pointers from the queue and place them into the \p ptr array. * * @return The number of pointers actually dequeued. * This number can be smaller than \p cnt in case the queue contained less than * \p cnt elements. */ int queue_pull_many(struct queue *q, void *ptr[], size_t cnt); /** Closes the queue, causing following writes to fail and following reads (after * the queue is empty) to fail. * * @return 0 on success. * @return -1 on failure. */ int queue_close(struct queue *q);