source: rtems/cpukit/score/src/schedulersimpleunblock.c @ 0a97ba5b

5
Last change on this file since 0a97ba5b was b8a5abf, checked in by Sebastian Huber <sebastian.huber@…>, on 02/26/15 at 09:33:36

score: Update _Thread_Heir only if necessary

Previously, the _Thread_Heir was updated unconditionally in case a new
heir was determined. The _Thread_Dispatch_necessary was only updated in
case the executing thread was preemptible or an internal thread was
unblocked. Change this to update the _Thread_Heir and
_Thread_Dispatch_necessary only in case the currently selected heir
thread is preemptible or a dispatch is forced. Move the schedule
decision into the change priority operation and use the schedule
operation only in rtems_task_mode() in case preemption is enabled or an
ASR dispatch is necessary. This is a behaviour change. Previously, the
RTEMS_NO_PREEMPT also prevented signal delivery in certain cases (not
always). Now, signal delivery is no longer influenced by
RTEMS_NO_PREEMPT. Since the currently selected heir thread is used to
determine if a new heir is chosen, non-preemptible heir threads
currently not executing now prevent a new heir. This may have an
application impact, see change test tm04. Document this change in sp04.

Update #2273.

  • Property mode set to 100644
File size: 1.4 KB
Line 
1/**
2 * @file
3 *
4 * @brief Scheduler Simple Handler / Unblock
5 * @ingroup ScoreScheduler
6 */
7
8/*
9 *  COPYRIGHT (c) 2011.
10 *  On-Line Applications Research Corporation (OAR).
11 *
12 *  The license and distribution terms for this file may be
13 *  found in 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/schedulersimpleimpl.h>
22#include <rtems/score/thread.h>
23
24Scheduler_Void_or_thread _Scheduler_simple_Unblock(
25  const Scheduler_Control *scheduler,
26  Thread_Control          *the_thread
27)
28{
29  Scheduler_simple_Context *context =
30    _Scheduler_simple_Get_context( scheduler );
31
32  _Scheduler_simple_Insert_priority_fifo( &context->Ready, the_thread );
33
34  /*
35   *  If the thread that was unblocked is more important than the heir,
36   *  then we have a new heir.  This may or may not result in a
37   *  context switch.
38   *
39   *  Normal case:
40   *    If the current thread is preemptible, then we need to do
41   *    a context switch.
42   *  Pseudo-ISR case:
43   *    Even if the thread isn't preemptible, if the new heir is
44   *    a pseudo-ISR system task, we need to do a context switch.
45   */
46  if ( the_thread->current_priority < _Thread_Heir->current_priority ) {
47    _Scheduler_Update_heir(
48      the_thread,
49      the_thread->current_priority == PRIORITY_PSEUDO_ISR
50    );
51  }
52
53  SCHEDULER_RETURN_VOID_OR_NULL;
54}
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