source: rtems/cpukit/score/src/threadqrequeue.c @ 2369b10

4.115
Last change on this file since 2369b10 was 91e7b0c, checked in by Sebastian Huber <sebastian.huber@…>, on 03/27/14 at 08:04:47

score: PR2172: _Thread_queue_Extract()

Add _Thread_queue_Extract_with_return_code(). On SMP this sequence in
_Thread_queue_Process_timeout() was broken:

[...]

/*

  • After we enable interrupts here, a lot may happen in the
  • meantime, e.g. nested interrupts may release the resource that
  • times out here. So we enter _Thread_queue_Extract()
  • speculatively. Inside this function we check the actual status
  • under ISR disable protection. This ensures that exactly one
  • executing context performs the extract operation (other parties
  • may call _Thread_queue_Dequeue()). If this context won, then
  • we have a timeout. *
  • We can use the_thread_queue pointer here even if
  • the_thread->Wait.queue is already set to NULL since the extract
  • operation will only use the thread queue discipline to select
  • the right extract operation. The timeout status is set during
  • thread queue initialization. */

we_did_it = _Thread_queue_Extract( the_thread_queue, the_thread );
if ( we_did_it ) {

the_thread->Wait.return_code = the_thread_queue->timeout_status;

}

[...]

In case _Thread_queue_Extract() successfully extracted a thread, then
this thread may start execution on a remote processor immediately and
read the the_thread->Wait.return_code before we update it here with the
timeout status. Thus it observes a successful operation even if it
timed out.
  • Property mode set to 100644
File size: 1.4 KB
Line 
1/**
2 *  @file
3 *
4 *  @brief Thread Queue Requeue
5 *  @ingroup ScoreThreadQ
6 */
7
8/*
9 *  COPYRIGHT (c) 1989-2008.
10 *  On-Line Applications Research Corporation (OAR).
11 *
12 *  The license and distribution terms for this file may be
13 *  found in the file LICENSE in this distribution or at
14 *  http://www.rtems.org/license/LICENSE.
15 */
16
17#if HAVE_CONFIG_H
18#include "config.h"
19#endif
20
21#include <rtems/score/threadqimpl.h>
22#include <rtems/score/statesimpl.h>
23
24void _Thread_queue_Requeue(
25  Thread_queue_Control *the_thread_queue,
26  Thread_Control       *the_thread
27)
28{
29  /*
30   * Just in case the thread really wasn't blocked on a thread queue
31   * when we get here.
32   */
33  if ( !the_thread_queue )
34    return;
35
36  /*
37   * If queueing by FIFO, there is nothing to do. This only applies to
38   * priority blocking discipline.
39   */
40  if ( the_thread_queue->discipline == THREAD_QUEUE_DISCIPLINE_PRIORITY ) {
41    Thread_queue_Control *tq = the_thread_queue;
42    ISR_Level             level;
43    ISR_Level             level_ignored;
44
45    _ISR_Disable( level );
46    if ( _States_Is_waiting_on_thread_queue( the_thread->current_state ) ) {
47      _Thread_queue_Enter_critical_section( tq );
48      _Thread_queue_Extract_priority_helper(
49        the_thread,
50        the_thread->Wait.return_code,
51        true
52      );
53      (void) _Thread_queue_Enqueue_priority( tq, the_thread, &level_ignored );
54    }
55    _ISR_Enable( level );
56  }
57}
58
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