source: rtems/cpukit/rtems/src/taskwakeafter.c @ 701dd96f

4.115
Last change on this file since 701dd96f was 701dd96f, checked in by Sebastian Huber <sebastian.huber@…>, on 06/12/14 at 12:37:57

score: PR2181: Add _Thread_Yield()

The _Scheduler_Yield() was called by the executing thread with thread
dispatching disabled and interrupts enabled. The rtems_task_suspend()
is explicitly allowed in ISRs:

http://rtems.org/onlinedocs/doc-current/share/rtems/html/c_user/Interrupt-Manager-Directives-Allowed-from-an-ISR.html#Interrupt-Manager-Directives-Allowed-from-an-ISR

Unlike the other scheduler operations the locking was performed inside
the operation. This lead to the following race condition. Suppose a
ISR suspends the executing thread right before the yield scheduler
operation. Now the executing thread is not longer in the set of ready
threads. The typical scheduler operations did not check the thread
state and will now extract the thread again and enqueue it. This
corrupted data structures.

Add _Thread_Yield() and do the scheduler yield operation with interrupts
disabled. This has a negligible effect on the interrupt latency.

  • Property mode set to 100644
File size: 1.1 KB
Line 
1/**
2 *  @file
3 *
4 *  @brief RTEMS Task Wake After
5 *  @ingroup ClassicTasks
6 */
7
8/*
9 *  COPYRIGHT (c) 1989-1999.
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/rtems/tasks.h>
22#include <rtems/score/threadimpl.h>
23#include <rtems/score/watchdogimpl.h>
24
25rtems_status_code rtems_task_wake_after(
26  rtems_interval ticks
27)
28{
29  /*
30   * It is critical to obtain the executing thread after thread dispatching is
31   * disabled on SMP configurations.
32   */
33  Thread_Control *executing;
34
35  _Thread_Disable_dispatch();
36    executing = _Thread_Executing;
37
38    if ( ticks == 0 ) {
39      _Thread_Yield( executing );
40    } else {
41      _Thread_Set_state( executing, STATES_DELAYING );
42      _Watchdog_Initialize(
43        &executing->Timer,
44        _Thread_Delay_ended,
45        executing->Object.id,
46        NULL
47      );
48      _Watchdog_Insert_ticks( &executing->Timer, ticks );
49    }
50  _Thread_Enable_dispatch();
51  return RTEMS_SUCCESSFUL;
52}
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