/* SPDX-License-Identifier: BSD-2-Clause */
/**
* @file
*
* @ingroup RTEMSScoreMessageQueue
*
* @brief This source file contains the implementation of
* _CORE_message_queue_Flush().
*/
/*
* COPYRIGHT (c) 1989-1999.
* On-Line Applications Research Corporation (OAR).
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. 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 OWNER 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.
*/
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
#include <rtems/score/coremsgimpl.h>
uint32_t _CORE_message_queue_Flush(
CORE_message_queue_Control *the_message_queue,
Thread_queue_Context *queue_context
)
{
Chain_Node *inactive_head;
Chain_Node *inactive_first;
Chain_Node *message_queue_first;
Chain_Node *message_queue_last;
uint32_t count;
/*
* Currently, RTEMS supports no API that has both flush and blocking
* sends. Thus, this routine assumes that there are no senders
* blocked waiting to send messages. In the event, that an API is
* added that can flush a message queue when threads are blocked
* waiting to send, there are two basic behaviors envisioned:
*
* (1) The thread queue of pending senders is a logical extension
* of the pending message queue. In this case, it should be
* flushed using the _Thread_queue_Flush_critical() service with a status
* such as CORE_MESSAGE_QUEUE_SENDER_FLUSHED (which currently does
* not exist). This can be implemented without changing the "big-O"
* of the message flushing part of the routine.
*
* (2) Only the actual messages queued should be purged. In this case,
* the blocked sender threads must be allowed to send their messages.
* In this case, the implementation will be forced to individually
* dequeue the senders and queue their messages. This will force
* this routine to have "big O(n)" where n is the number of blocked
* senders. If there are more messages pending than senders blocked,
* then the existing flush code can be used to dispose of the remaining
* pending messages.
*
* For now, though, we are very happy to have a small routine with
* fixed execution time that only deals with pending messages.
*/
_CORE_message_queue_Acquire_critical( the_message_queue, queue_context );
count = the_message_queue->number_of_pending_messages;
if ( count != 0 ) {
the_message_queue->number_of_pending_messages = 0;
inactive_head = _Chain_Head( &the_message_queue->Inactive_messages );
inactive_first = inactive_head->next;
message_queue_first = _Chain_First( &the_message_queue->Pending_messages );
message_queue_last = _Chain_Last( &the_message_queue->Pending_messages );
inactive_head->next = message_queue_first;
message_queue_last->next = inactive_first;
inactive_first->previous = message_queue_last;
message_queue_first->previous = inactive_head;
_Chain_Initialize_empty( &the_message_queue->Pending_messages );
}
_CORE_message_queue_Release( the_message_queue, queue_context );
return count;
}
