source: rtems/cpukit/score/src/schedulersimpleunblock.c @ 25f5730f

4.115
Last change on this file since 25f5730f was f39f667a, checked in by Sebastian Huber <sebastian.huber@…>, on 05/14/14 at 11:50:48

score: Simplify _Thread_Change_priority()

The function to change a thread priority was too complex. Simplify it
with a new scheduler operation. This increases the average case
performance due to the simplified logic. The interrupt disabled
critical section is a bit prolonged since now the extract, update and
enqueue steps are executed atomically. This should however not impact
the worst-case interrupt latency since at least for the Deterministic
Priority Scheduler this sequence can be carried out with a wee bit of
instructions and no loops.

Add _Scheduler_Change_priority() to replace the sequence of

  • _Thread_Set_transient(),
  • _Scheduler_Extract(),
  • _Scheduler_Enqueue(), and
  • _Scheduler_Enqueue_first().

Delete STATES_TRANSIENT, _States_Is_transient() and
_Thread_Set_transient() since this state is now superfluous.

With this change it is possible to get rid of the
SCHEDULER_SMP_NODE_IN_THE_AIR state. This considerably simplifies the
implementation of the new SMP locking protocols.

  • 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
24void _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    _Thread_Heir = the_thread;
48    if ( _Thread_Executing->is_preemptible ||
49        the_thread->current_priority == 0 )
50      _Thread_Dispatch_necessary = true;
51  }
52}
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