/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (the "License").
 * You may not use this file except in compliance with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */

/*
 * Copyright (c) 2002-2003, Network Appliance, Inc. All rights reserved.
 */

/*
 * Copyright 2007 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

/*
 *
 * MODULE: dapl_evd_dequeue.c
 *
 * PURPOSE: Event Management
 *
 * Description:  Interfaces in this file are completely described in
 *               the uDAPL 1.1 API, Chapter 6, section 3
 *
 * $Id: dapl_evd_dequeue.c,v 1.9 2003/07/30 18:13:38 hobie16 Exp $
 */

#include "dapl.h"
#include "dapl_ring_buffer_util.h"
#include "dapl_evd_util.h"

/*
 * dapl_evd_dequeue
 *
 * DAPL Requirements Version xxx, 6.3.2.7
 *
 * Remove first element from an event dispatcher
 *
 * Input:
 *      evd_handle
 *
 * Output:
 *      event
 *
 * Returns:
 *      DAT_SUCCESS
 *      DAT_INVALID_HANDLE
 *      DAT_INVALID_PARAMETER
 *      DAT_INVALID_STATE
 *      DAT_QUEUE_EMPTY
 */

DAT_RETURN dapl_evd_dequeue(
    IN    DAT_EVD_HANDLE        evd_handle,
    OUT   DAT_EVENT             *event)
{
        DAPL_EVD        *evd_ptr;
        DAT_EVENT       *local_event;
        DAT_RETURN      dat_status;

        dapl_dbg_log(DAPL_DBG_TYPE_API,
            "dapl_evd_dequeue (%p, %p)\n",
            evd_handle,
            event);

        evd_ptr = (DAPL_EVD *)evd_handle;
        dat_status = DAT_SUCCESS;

        if (DAPL_BAD_HANDLE(evd_handle, DAPL_MAGIC_EVD)) {
                dat_status = DAT_ERROR(DAT_INVALID_HANDLE, 0);
                goto bail;
        }

        if (event == NULL) {
                dat_status = DAT_ERROR(DAT_INVALID_PARAMETER, DAT_INVALID_ARG2);
                goto bail;
        }

        /*
         * We need to dequeue under lock, as the IB OS Access API
         * restricts us from having multiple threads in CQ poll, and the
         * DAPL 1.1 API allows multiple threads in dat_evd_dequeue()
         */
        dapl_os_lock(&evd_ptr->header.lock);

        /*
         * Make sure there are no other waiters and the evd is active.
         * Currently this means only the OPEN state is allowed.
         */
        if (evd_ptr->evd_state != DAPL_EVD_STATE_OPEN ||
            evd_ptr->catastrophic_overflow) {
                dapl_os_unlock(&evd_ptr->header.lock);
                dat_status = DAT_ERROR(DAT_INVALID_STATE, 0);
                goto bail;
        }

        /*
         * Try the EVD rbuf first; poll from the CQ only if that's empty.
         * This keeps events in order if dat_evd_wait() has copied events
         * from CQ to EVD.
         */
        if (evd_ptr->pending_event_queue.head !=
            evd_ptr->pending_event_queue.tail) {
                local_event = (DAT_EVENT *)
                    dapls_rbuf_remove(&evd_ptr->pending_event_queue);
                if (local_event != NULL) {
                        *event = *local_event;
                        dat_status = dapls_rbuf_add(&evd_ptr->free_event_queue,
                            local_event);
                } else { /* should never happen */
                        dat_status = DAT_ERROR(DAT_INTERNAL_ERROR, 0);
                }
        } else if (evd_ptr->ib_cq_handle == IB_INVALID_HANDLE) {
                dat_status =  DAT_ERROR(DAT_QUEUE_EMPTY, 0);
        } else if ((evd_ptr->evd_flags & (DAT_EVD_CONNECTION_FLAG |
            DAT_EVD_CR_FLAG | DAT_EVD_ASYNC_FLAG)) == 0) {
                /*
                 * No need to drop into kernel, just check the CQ.
                 */
                dat_status = dapls_evd_cq_poll_to_event(evd_ptr, event);
        } else {
                /* poll for events with threshold and timeout both 0 */
                evd_ptr->threshold = 0;

                dapl_os_unlock(&evd_ptr->header.lock);
                dat_status = dapls_evd_copy_events(evd_ptr, 0);
                if (dat_status != DAT_SUCCESS) {
                        dat_status = DAT_ERROR(DAT_QUEUE_EMPTY, 0);
                        goto bail;
                }

                dapl_os_lock(&evd_ptr->header.lock);

                local_event = (DAT_EVENT *)dapls_rbuf_remove(
                    &evd_ptr->pending_event_queue);
                if (local_event != NULL) {
                        *event = *local_event;
                        dat_status = dapls_rbuf_add(&evd_ptr->free_event_queue,
                            local_event);
                } else { /* still didn't find anything */
                        dat_status =  DAT_ERROR(DAT_QUEUE_EMPTY, 0);
                }
        }

        dapl_os_unlock(&evd_ptr->header.lock);
bail:
        dapl_dbg_log(DAPL_DBG_TYPE_RTN,
            "dapl_evd_dequeue () returns 0x%x\n",
            dat_status);

        return (dat_status);
}