source: rtems/cpukit/score/src/coremsgflushsupp.c @ c499856

4.11
Last change on this file since c499856 was c499856, checked in by Chris Johns <chrisj@…>, on Mar 20, 2014 at 9:10:47 PM

Change all references of rtems.com to rtems.org.

  • Property mode set to 100644
File size: 2.9 KB
Line 
1/**
2 * @file
3 *
4 * @brief Flush Messages Support Routine
5 *
6 * @ingroup ScoreMessageQueue
7 */
8
9/*
10 *  COPYRIGHT (c) 1989-1999.
11 *  On-Line Applications Research Corporation (OAR).
12 *
13 *  The license and distribution terms for this file may be
14 *  found in the file LICENSE in this distribution or at
15 *  http://www.rtems.org/license/LICENSE.
16 */
17
18#if HAVE_CONFIG_H
19#include "config.h"
20#endif
21
22#include <rtems/system.h>
23#include <rtems/score/chain.h>
24#include <rtems/score/isr.h>
25#include <rtems/score/coremsgimpl.h>
26#include <rtems/score/thread.h>
27#include <rtems/score/wkspace.h>
28
29uint32_t   _CORE_message_queue_Flush_support(
30  CORE_message_queue_Control *the_message_queue
31)
32{
33  ISR_Level   level;
34  Chain_Node *inactive_head;
35  Chain_Node *inactive_first;
36  Chain_Node *message_queue_first;
37  Chain_Node *message_queue_last;
38  uint32_t    count;
39
40  /*
41   *  Currently, RTEMS supports no API that has both flush and blocking
42   *  sends.  Thus, this routine assumes that there are no senders
43   *  blocked waiting to send messages.  In the event, that an API is
44   *  added that can flush a message queue when threads are blocked
45   *  waiting to send, there are two basic behaviors envisioned:
46   *
47   *  (1) The thread queue of pending senders is a logical extension
48   *  of the pending message queue.  In this case, it should be
49   *  flushed using the _Thread_queue_Flush() service with a status
50   *  such as CORE_MESSAGE_QUEUE_SENDER_FLUSHED (which currently does
51   *  not exist).  This can be implemented without changing the "big-O"
52   *  of the message flushing part of the routine.
53   *
54   *  (2) Only the actual messages queued should be purged.  In this case,
55   *  the blocked sender threads must be allowed to send their messages.
56   *  In this case, the implementation will be forced to individually
57   *  dequeue the senders and queue their messages.  This will force
58   *  this routine to have "big O(n)" where n is the number of blocked
59   *  senders.  If there are more messages pending than senders blocked,
60   *  then the existing flush code can be used to dispose of the remaining
61   *  pending messages.
62   *
63   *  For now, though, we are very happy to have a small routine with
64   *  fixed execution time that only deals with pending messages.
65   */
66
67  _ISR_Disable( level );
68    inactive_head = _Chain_Head( &the_message_queue->Inactive_messages );
69    inactive_first = inactive_head->next;
70    message_queue_first = _Chain_First( &the_message_queue->Pending_messages );
71    message_queue_last = _Chain_Last( &the_message_queue->Pending_messages );
72
73    inactive_head->next = message_queue_first;
74    message_queue_last->next = inactive_first;
75    inactive_first->previous = message_queue_last;
76    message_queue_first->previous = inactive_head;
77
78    _Chain_Initialize_empty( &the_message_queue->Pending_messages );
79
80    count = the_message_queue->number_of_pending_messages;
81    the_message_queue->number_of_pending_messages = 0;
82  _ISR_Enable( level );
83  return count;
84}
Note: See TracBrowser for help on using the repository browser.