2011-09-15 Petr Benes <benesp16@fel.cvut.cz>

	PR 1906/cpukit
	* sapi/Makefile.am, sapi/preinstall.am, sapi/include/confdefs.h,
	score/Makefile.am, score/preinstall.am: Add the CBS (Constant
	Bandwidth Server) scheduler. This is a complex scheduling policy
	built atop of the EDF scheduler. Unlike other schedulers, this one
	provides a user API and handles not only deadlines of tasks but also
	claimed budget per period. The main aim of the scheduler is isolation
	of tasks so that each task is guaranteed to meet all deadlines
	regardless of how other tasks behave.
	* sapi/include/rtems/cbs.h, sapi/inline/rtems/cbs.inl,
	score/include/rtems/score/schedulercbs.h, score/src/schedulercbs.c,
	score/src/schedulercbsattachthread.c,
	score/src/schedulercbscleanup.c,
	score/src/schedulercbscreateserver.c,
	score/src/schedulercbsdestroyserver.c,
	score/src/schedulercbsdetachthread.c,
	score/src/schedulercbsgetapprovedbudget.c,
	score/src/schedulercbsgetexecutiontime.c,
	score/src/schedulercbsgetparameters.c,
	score/src/schedulercbsgetremainingbudget.c,
	score/src/schedulercbsgetserverid.c,
	score/src/schedulercbsreleasejob.c,
	score/src/schedulercbssetparameters.c,
	score/src/schedulercbsunblock.c: New files.

1 files changed, 76 insertions, 0 deletions

diff --git a/cpukit/score/src/schedulercbsunblock.c b/cpukit/score/src/schedulercbsunblock.c
new file mode 100644
index 0000000000..0f417d8c9e
--- /dev/null
+++ b/cpukit/score/src/schedulercbsunblock.c
@@ -0,0 +1,76 @@
+/*
+ *  Copyright (C) 2011 Petr Benes.
+ *  Copyright (C) 2011 On-Line Applications Research Corporation (OAR).
+ *
+ *  The license and distribution terms for this file may be
+ *  found in the file LICENSE in this distribution or at
+ *  http://www.rtems.com/license/LICENSE.
+ *
+ *  $Id$
+ */
+
+#if HAVE_CONFIG_H
+#include "config.h"
+#endif
+
+#include <rtems/system.h>
+#include <rtems/score/scheduler.h>
+#include <rtems/score/schedulercbs.h>
+
+void _Scheduler_CBS_Unblock(
+  Thread_Control    *the_thread
+)
+{
+  Scheduler_CBS_Per_thread *sched_info;
+  Scheduler_CBS_Server *serv_info;
+  Priority_Control new_priority;
+
+  _Scheduler_EDF_Enqueue(the_thread);
+  /* TODO: flash critical section? */
+
+  sched_info = (Scheduler_CBS_Per_thread *) the_thread->scheduler_info;
+  serv_info = (Scheduler_CBS_Server *) sched_info->cbs_server;
+
+  /*
+   * Late unblock rule for deadline-driven tasks. The remaining time to
+   * deadline must be sufficient to serve the remaining computation time
+   * without increased utilization of this task. It might cause a deadline
+   * miss of another task.
+   */
+  if (serv_info) {
+    time_t deadline = serv_info->parameters.deadline;
+    time_t budget = serv_info->parameters.budget;
+    time_t deadline_left = the_thread->cpu_time_budget;
+    time_t budget_left = the_thread->real_priority -
+                           _Watchdog_Ticks_since_boot;
+
+    if ( deadline*budget_left > budget*deadline_left ) {
+      /* Put late unblocked task to background until the end of period. */
+      new_priority = the_thread->Start.initial_priority;
+      if ( the_thread->real_priority != new_priority )
+        the_thread->real_priority = new_priority;
+      if ( the_thread->current_priority != new_priority )
+        _Thread_Change_priority(the_thread, new_priority, true);
+    }
+  }
+
+  /*
+   *  If the thread that was unblocked is more important than the heir,
+   *  then we have a new heir.  This may or may not result in a
+   *  context switch.
+   *
+   *  Normal case:
+   *    If the current thread is preemptible, then we need to do
+   *    a context switch.
+   *  Pseudo-ISR case:
+   *    Even if the thread isn't preemptible, if the new heir is
+   *    a pseudo-ISR system task, we need to do a context switch.
+   */
+  if ( _Scheduler_Is_priority_higher_than( the_thread->current_priority,
+       _Thread_Heir->current_priority)) {
+    _Thread_Heir = the_thread;
+    if ( _Thread_Executing->is_preemptible ||
+         the_thread->current_priority == 0 )
+      _Thread_Dispatch_necessary = true;
+  }
+}