source: rtems/cpukit/score/src/schedulerdefaultaskforhelp.c @ 99fc1d1d

5
Last change on this file since 99fc1d1d was 5c3d250, checked in by Sebastian Huber <sebastian.huber@…>, on 07/04/14 at 12:34:23

score: Implement scheduler helping protocol

The following scheduler operations return a thread in need for help

  • unblock,
  • change priority, and
  • yield.

A thread in need for help is a thread that encounters a scheduler state
change from scheduled to ready or a thread that cannot be scheduled in
an unblock operation. Such a thread can ask threads which depend on
resources owned by this thread for help.

Add a new ask for help scheduler operation. This operation is used by
_Scheduler_Ask_for_help() to help threads in need for help returned by
the operations mentioned above. This operation is also used by
_Scheduler_Thread_change_resource_root() in case the root of a resource
sub-tree changes. A use case is the ownership change of a resource.

In case it is not possible to schedule a thread in need for help, then
the corresponding scheduler node will be placed into the set of ready
scheduler nodes of the scheduler instance. Once a state change from
ready to scheduled happens for this scheduler node it may be used to
schedule the thread in need for help.
  • Property mode set to 100644
File size: 544 bytes
Line 
1/*
2 * Copyright (c) 2014 embedded brains GmbH
3 *
4 * The license and distribution terms for this file may be
5 * found in the file LICENSE in this distribution or at
6 * http://www.rtems.org/license/LICENSE.
7 */
8
9#if HAVE_CONFIG_H
10  #include "config.h"
11#endif
12
13#include <rtems/score/scheduler.h>
14
15Thread_Control *_Scheduler_default_Ask_for_help(
16  const Scheduler_Control *scheduler,
17  Thread_Control          *offers_help,
18  Thread_Control          *needs_help
19)
20{
21  (void) scheduler;
22  (void) offers_help;
23  (void) needs_help;
24
25  return NULL;
26}
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