bev_cqueue.c

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/* -*- C -*- */
/*
 * Copyright (c) 2012-2020 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.
 *
 */


static bool bev_cqueue_invariant(const struct nlx_core_bev_cqueue *q)
{
        return q != NULL && q->cbcq_consumer != 0 &&
            q->cbcq_nr >= M0_NET_LNET_BEVQ_MIN_SIZE &&
            m0_atomic64_get(&q->cbcq_count) < q->cbcq_nr &&
            !nlx_core_kmem_loc_is_empty(&q->cbcq_producer_loc);
}

static void bev_cqueue_add(struct nlx_core_bev_cqueue *q,
                           struct nlx_core_bev_link *ql)
{
        struct nlx_core_bev_link *consumer =
            (struct nlx_core_bev_link *) (q->cbcq_consumer);
        M0_PRE(q->cbcq_nr > 0 && consumer != NULL);
        M0_PRE(nlx_core_kmem_loc_invariant(&ql->cbl_p_self_loc));
        ql->cbl_c_self = (nlx_core_opaque_ptr_t) ql;

        ql->cbl_c_next = consumer->cbl_c_next;
        ql->cbl_p_next_loc = consumer->cbl_p_next_loc;
        consumer->cbl_c_next = (nlx_core_opaque_ptr_t) ql;
        consumer->cbl_p_next_loc = ql->cbl_p_self_loc;
        q->cbcq_consumer = (nlx_core_opaque_ptr_t) ql;
        q->cbcq_nr++;

        M0_POST(bev_cqueue_invariant(q));
}

static void bev_cqueue_init(struct nlx_core_bev_cqueue *q,
                            struct nlx_core_bev_link *ql1,
                            struct nlx_core_bev_link *ql2)
{
        M0_PRE(q != NULL && q->cbcq_nr == 0 && ql1 != NULL && ql2 != NULL);
        M0_PRE(nlx_core_kmem_loc_invariant(&ql1->cbl_p_self_loc));
        /* special case: add first element to the circular queue */
        ql1->cbl_c_self = (nlx_core_opaque_ptr_t) ql1;
        ql1->cbl_c_next = (nlx_core_opaque_ptr_t) ql1;
        ql1->cbl_p_next_loc = ql1->cbl_p_self_loc;
        q->cbcq_consumer = (nlx_core_opaque_ptr_t) ql1;
        q->cbcq_producer_loc = ql1->cbl_p_self_loc;
        q->cbcq_nr++;

        bev_cqueue_add(q, ql2);
        m0_atomic64_set(&q->cbcq_count, 0);
        M0_POST(bev_cqueue_invariant(q));
}

static void bev_cqueue_fini(struct nlx_core_bev_cqueue *q,
                            void (*free_cb)(struct nlx_core_bev_link *))
{
        struct nlx_core_bev_link *ql;
        struct nlx_core_bev_link *nql = NULL;

        M0_PRE(bev_cqueue_invariant(q));
        M0_PRE(free_cb != NULL);
        for (ql = (struct nlx_core_bev_link *) q->cbcq_consumer;
             q->cbcq_nr > 0; ql = nql, --q->cbcq_nr) {
                nql = (struct nlx_core_bev_link *) ql->cbl_c_next;
                free_cb(ql);
        }

        q->cbcq_consumer = 0;
}

static bool bev_cqueue_is_empty(const struct nlx_core_bev_cqueue *q)
{
        M0_PRE(bev_cqueue_invariant(q));
        return m0_atomic64_get(&q->cbcq_count) == 0;
}

static size_t bev_cqueue_size(const struct nlx_core_bev_cqueue *q)
{
        return q->cbcq_nr;
}

static struct nlx_core_bev_link *bev_cqueue_get(struct nlx_core_bev_cqueue *q)
{
        struct nlx_core_bev_link *link;

        if (bev_cqueue_is_empty(q)) /* also checks invariant */
                return NULL;
        link = (struct nlx_core_bev_link *) q->cbcq_consumer;
        M0_ASSERT(link->cbl_c_next != 0);
        q->cbcq_consumer = (nlx_core_opaque_ptr_t) link->cbl_c_next;
        m0_atomic64_dec(&q->cbcq_count);
        return (struct nlx_core_bev_link *) (q->cbcq_consumer);
}

/*
 *  Local variables:
 *  c-indentation-style: "K&R"
 *  c-basic-offset: 8
 *  tab-width: 8
 *  fill-column: 80
 *  scroll-step: 1
 *  End:
 */