queue.h

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/* -*- C -*- */
/*
 * Copyright (c) 2015-2020 Seagate Technology LLC and/or its Affiliates
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 * For any questions about this software or licensing,
 * please email opensource@seagate.com or cortx-questions@seagate.com.
 *
 */


#pragma once

#ifndef __MOTR_BE_QUEUE_H__
#define __MOTR_BE_QUEUE_H__

#include "lib/types.h"          /* m0_bcount_t */
#include "lib/tlist.h"          /* m0_tl */
#include "lib/mutex.h"          /* m0_mutex */

#include "be/tx_credit.h"       /* m0_be_tx_credit */


struct m0_be_op;
struct be_queue_wait_op;
struct m0_buf;

struct m0_be_queue_cfg {
        uint64_t    bqc_q_size_max;
        uint64_t    bqc_producers_nr_max;
        uint64_t    bqc_consumers_nr_max;
        m0_bcount_t bqc_item_length;
};

struct m0_be_queue {
        struct m0_be_queue_cfg   bq_cfg;
        struct m0_mutex          bq_lock;

        struct m0_tl             bq_q;
        struct m0_tl             bq_q_unused;

        char                    *bq_qitems;

        struct m0_tl             bq_op_put;
        struct m0_tl             bq_op_put_unused;
        struct m0_tl             bq_op_get;
        struct m0_tl             bq_op_get_unused;

        struct be_queue_wait_op *bq_ops_get;
        struct be_queue_wait_op *bq_ops_put;

        bool                     bq_the_end;

        uint64_t                 bq_enqueued;
        uint64_t                 bq_dequeued;
};

#define BEQ_F "(queue=%p bq_enqueued=%" PRIu64 " bq_dequeued=%" PRIu64 " " \
        "bq_the_end=%d)"
#define BEQ_P(bq) (bq), (bq)->bq_enqueued, (bq)->bq_dequeued, \
        !!((bq)->bq_the_end)

M0_INTERNAL int m0_be_queue_init(struct m0_be_queue     *bq,
                                 struct m0_be_queue_cfg *cfg);
M0_INTERNAL void m0_be_queue_fini(struct m0_be_queue *bq);

M0_INTERNAL void m0_be_queue_lock(struct m0_be_queue *bq);
M0_INTERNAL void m0_be_queue_unlock(struct m0_be_queue *bq);

/*
 * Put a buffer to the queue.
 *
 * @param data  the data from this buffer is copied to the queue internal data
 *              structures
 *
 * @pre data->b_nob == bq->bq_cfg.bqc_item_length
 *
 * - if the queue is full, then the operation would block until a space for at
 *   least one item becomes available in the queue;
 * - different producers waiting on m0_be_queue_put() would be awaken in the
 *   same order they were put to sleep.
 */
M0_INTERNAL void m0_be_queue_put(struct m0_be_queue  *bq,
                                 struct m0_be_op     *op,
                                 const struct m0_buf *data);

/*
 * Nothing is going to be put to the queue after this call.
 * This function could be called only once.
 */
M0_INTERNAL void m0_be_queue_end(struct m0_be_queue *bq);

/*
 * Get a buffer from the queue.
 *
 * @param data          The data is copied from queue internal data structures
 *                      to the buffer this parameter points to.
 * @param successful    true if the data is returned, false if the queue is
 *                      empty and m0_be_queue_end() has been called before this
 *                      call.
 *
 * @pre data->b_nob == bq->bq_cfg.bqc_item_length
 *
 * - if the queue is empty, then the operation would block until at least one
 *   item becomes available in the queue;
 * - different consumers waiting on m0_be_queue_get() would be awaken in the
 *   same order they were put to sleep.
 */
M0_INTERNAL void m0_be_queue_get(struct m0_be_queue *bq,
                                 struct m0_be_op    *op,
                                 struct m0_buf      *data,
                                 bool               *successful);

/*
 * Peek at the queue.
 *
 * @param data  the buffer that is in the queue internal data structures is
 *              copied to the memory data parameter points to.
 * @return      true if the data was copied, false if the queue is empty.
 *
 * @pre data->b_nob == bq->bq_cfg.bqc_item_length
 */
M0_INTERNAL bool m0_be_queue_peek(struct m0_be_queue *bq,
                                  struct m0_buf      *data);

#define M0_BE_QUEUE_PUT(bq, op, ptr)                                           \
                m0_be_queue_put(bq, op, &M0_BUF_INIT_PTR(ptr))
#define M0_BE_QUEUE_GET(bq, op, ptr, successful)                               \
                m0_be_queue_get(bq, op, &M0_BUF_INIT_PTR(ptr), successful)
#define M0_BE_QUEUE_PEEK(bq, ptr)                                              \
                m0_be_queue_peek(bq, &M0_BUF_INIT_PTR(ptr))

#endif /* __MOTR_BE_QUEUE_H__ */

/*
 *  Local variables:
 *  c-indentation-style: "K&R"
 *  c-basic-offset: 8
 *  tab-width: 8
 *  fill-column: 80
 *  scroll-step: 1
 *  End:
 */
/*
 * vim: tabstop=8 shiftwidth=8 noexpandtab textwidth=80 nowrap
 */