2011-03-16 Jennifer Averett <jennifer.averett@OARcorp.com>

	PR 1743/cpu
	* sapi/include/confdefs.h, score/Makefile.am, score/preinstall.am: Add
	Simple Priority Scheduler as complement to existing Deterministic
	Priority Scheduler. This scheduler serves both as an example and as a
	lighter weight implementation for smaller systems.
	* score/include/rtems/score/schedulersimple.h,
	score/inline/rtems/score/schedulersimple.inl,
	score/src/schedulersimple.c, score/src/schedulersimpleblock.c,
	score/src/schedulersimpleenqueue.c,
	score/src/schedulersimpleenqueuefirst.c,
	score/src/schedulersimpleextract.c,
	score/src/schedulersimplereadyqueueenqueue.c,
	score/src/schedulersimplereadyqueueenqueuefirst.c,
	score/src/schedulersimpleschedule.c,
	score/src/schedulersimpleunblock.c, score/src/schedulersimpleyield.c:
	New files.

10 files changed, 431 insertions, 0 deletions

diff --git a/cpukit/score/src/schedulersimple.c b/cpukit/score/src/schedulersimple.c
new file mode 100644
index 0000000000..7a7ed944f4
--- /dev/null
+++ b/cpukit/score/src/schedulersimple.c
@@ -0,0 +1,84 @@
+/*
+ *  Scheduler Simple Handler / Initialize
+ *  Scheduler Simple Handler / Allocate (Empty Routine)
+ *  Scheduler Simple Handler / Update (Empty Routine)
+ *  Scheduler Simple Handler / Free (Empty Routine)
+ *
+ *  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/config.h>
+#include <rtems/score/chain.h>
+#include <rtems/score/scheduler.h>
+#include <rtems/score/schedulersimple.h>
+#include <rtems/score/thread.h>
+#include <rtems/score/wkspace.h>
+
+/**
+ * This routine does nothing, and is used as a stub for Schedule allocate
+ *
+ * Note: returns a non-zero value, or else thread initialize thinks the 
+ * allocation failed.
+ *
+ * The overhead of a function call will still be imposed.
+ */
+void * _Scheduler_simple_Allocate( 
+  Thread_Control *the_thread
+)
+{
+  return (void*)-1; /* maybe pick an appropriate poison value */
+}
+
+
+/**
+ * This routine does nothing, and is used as a stub for Schedule update
+ *
+ * The overhead of a function call will still be imposed.
+ */
+void _Scheduler_simple_Update( 
+  Thread_Control *the_thread
+)
+{
+}
+
+/**
+ * This routine does nothing, and is used as a stub for Schedule free
+ *
+ * The overhead of a function call will still be imposed.
+ */
+void _Scheduler_simple_Free( 
+  Thread_Control *the_thread
+)
+{
+}
+
+/**
+ * This routine initializes the simple scheduler.
+ */
+void _Scheduler_simple_Initialize ( void )
+{
+  void *f;
+
+  /* 
+   * Initialize Ready Queue
+   */
+
+  /* allocate ready queue structures */
+  f = _Workspace_Allocate_or_fatal_error( sizeof(Chain_Control) );
+  _Scheduler.information = f;
+
+  /* initialize ready queue structure */
+  _Chain_Initialize_empty( (Chain_Control *)f );
+}
diff --git a/cpukit/score/src/schedulersimpleblock.c b/cpukit/score/src/schedulersimpleblock.c
new file mode 100644
index 0000000000..212f4f10bf
--- /dev/null
+++ b/cpukit/score/src/schedulersimpleblock.c
@@ -0,0 +1,39 @@
+/*
+ *  Scheduler Simple Handler / Block
+ *
+ *  COPYRIGHT (c) 2011.
+ *  On-Line Applications Research Corporation (OAR).
+ *
+ *  The license and distribution terms for this file may be
+ *  found in 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/context.h>
+#include <rtems/score/interr.h>
+#include <rtems/score/isr.h>
+#include <rtems/score/object.h>
+#include <rtems/score/priority.h>
+#include <rtems/score/scheduler.h>
+#include <rtems/score/thread.h>
+#include <rtems/score/schedulersimple.h>
+
+void _Scheduler_simple_Block(
+  Thread_Control   *the_thread
+)
+{
+  _Scheduler_simple_Extract(the_thread);
+
+  if ( _Thread_Is_heir( the_thread ) )
+    _Scheduler_simple_Schedule();
+
+  if ( _Thread_Is_executing( the_thread ) )
+    _Thread_Dispatch_necessary = true;
+}
diff --git a/cpukit/score/src/schedulersimpleenqueue.c b/cpukit/score/src/schedulersimpleenqueue.c
new file mode 100644
index 0000000000..8e5e6381c5
--- /dev/null
+++ b/cpukit/score/src/schedulersimpleenqueue.c
@@ -0,0 +1,29 @@
+/*
+ *  Schedule Simple Handler / Enqueue
+ *
+ *  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/chain.h>
+#include <rtems/score/isr.h>
+#include <rtems/score/thread.h>
+#include <rtems/score/schedulersimple.h>
+
+void _Scheduler_simple_Enqueue(
+  Thread_Control            *the_thread
+)
+{
+  _Scheduler_simple_Ready_queue_Enqueue( the_thread );
+}
diff --git a/cpukit/score/src/schedulersimpleenqueuefirst.c b/cpukit/score/src/schedulersimpleenqueuefirst.c
new file mode 100644
index 0000000000..d6fd7dda98
--- /dev/null
+++ b/cpukit/score/src/schedulersimpleenqueuefirst.c
@@ -0,0 +1,28 @@
+/*
+ *  Schedule Simple Handler / Enqueue First
+ *
+ *  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/chain.h>
+#include <rtems/score/thread.h>
+#include <rtems/score/schedulersimple.h>
+
+void _Scheduler_simple_Enqueue_first(
+  Thread_Control            *the_thread
+)
+{
+  _Scheduler_simple_Ready_queue_Enqueue_first( the_thread );
+}
diff --git a/cpukit/score/src/schedulersimpleextract.c b/cpukit/score/src/schedulersimpleextract.c
new file mode 100644
index 0000000000..208fcb55bd
--- /dev/null
+++ b/cpukit/score/src/schedulersimpleextract.c
@@ -0,0 +1,28 @@
+/*
+ *  Schedule Simple Handler / Extract 
+ *
+ *  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/chain.h>
+#include <rtems/score/thread.h>
+#include <rtems/score/schedulersimple.h>
+
+void _Scheduler_simple_Extract(
+  Thread_Control    *the_thread
+)
+{
+  _Chain_Extract_unprotected( &the_thread->Object.Node );
+}
diff --git a/cpukit/score/src/schedulersimplereadyqueueenqueue.c b/cpukit/score/src/schedulersimplereadyqueueenqueue.c
new file mode 100644
index 0000000000..788f94b20b
--- /dev/null
+++ b/cpukit/score/src/schedulersimplereadyqueueenqueue.c
@@ -0,0 +1,48 @@
+/*
+ *  Schedule Simple Handler / Ready Queue Enqueue
+ *
+ *  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/chain.h>
+#include <rtems/score/isr.h>
+#include <rtems/score/thread.h>
+#include <rtems/score/schedulersimple.h>
+
+void _Scheduler_simple_Ready_queue_Enqueue(
+  Thread_Control    *the_thread
+)
+{
+  Chain_Control    *ready;
+  Chain_Node       *the_node;
+  Thread_Control   *current;
+
+  ready    = (Chain_Control *)_Scheduler.information;
+  the_node = _Chain_First( ready );
+  current  = (Thread_Control *)ready;
+
+  for ( ; !_Chain_Is_tail( ready, the_node ) ; the_node = the_node->next ) {
+    current = (Thread_Control *) the_node;
+
+    /* break when AT END OR PAST our priority */
+    if ( the_thread->current_priority < current->current_priority ) {
+      current = (Thread_Control *)current->Object.Node.previous;
+      break;
+    }
+  }
+
+  /* enqueue */
+  _Chain_Insert_unprotected( (Chain_Node *)current, &the_thread->Object.Node );
+}
diff --git a/cpukit/score/src/schedulersimplereadyqueueenqueuefirst.c b/cpukit/score/src/schedulersimplereadyqueueenqueuefirst.c
new file mode 100644
index 0000000000..dee0bbd116
--- /dev/null
+++ b/cpukit/score/src/schedulersimplereadyqueueenqueuefirst.c
@@ -0,0 +1,52 @@
+/*
+ *  Schedule Simple Handler / Ready Queue Enqueue First
+ *
+ *  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/chain.h>
+#include <rtems/score/thread.h>
+#include <rtems/score/schedulersimple.h>
+
+void _Scheduler_simple_Ready_queue_Enqueue_first(
+  Thread_Control    *the_thread
+)
+{
+  Chain_Control    *ready;
+  Chain_Node       *the_node;
+  Thread_Control   *current;
+
+  ready    = (Chain_Control *)_Scheduler.information;
+  current  = (Thread_Control *)ready;
+
+  /*
+   * Do NOT need to check for end of chain because there is always
+   * at least one task on the ready chain -- the IDLE task.  It can
+   * never block, should never attempt to obtain a semaphore or mutex,
+   * and thus will always be there.
+   */
+  for ( the_node = _Chain_First(ready) ; ; the_node = the_node->next ) {
+    current = (Thread_Control *) the_node;
+
+    /* break when AT HEAD OF (or PAST) our priority */
+    if ( the_thread->current_priority <= current->current_priority ) {
+      current = (Thread_Control *)current->Object.Node.previous;
+      break;
+    }
+  }
+
+  /* enqueue */
+  _Chain_Insert_unprotected( (Chain_Node *)current, &the_thread->Object.Node );
+}
diff --git a/cpukit/score/src/schedulersimpleschedule.c b/cpukit/score/src/schedulersimpleschedule.c
new file mode 100644
index 0000000000..354e61f705
--- /dev/null
+++ b/cpukit/score/src/schedulersimpleschedule.c
@@ -0,0 +1,34 @@
+/*
+ *  Scheduler Simple Handler / Schedule
+ *
+ *  COPYRIGHT (c) 2011.
+ *  On-Line Applications Research Corporation (OAR).
+ *
+ *  The license and distribution terms for this file may be
+ *  found in 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/context.h>
+#include <rtems/score/interr.h>
+#include <rtems/score/isr.h>
+#include <rtems/score/object.h>
+#include <rtems/score/priority.h>
+#include <rtems/score/percpu.h>
+#include <rtems/score/scheduler.h>
+#include <rtems/score/thread.h>
+#include <rtems/score/schedulersimple.h>
+
+void _Scheduler_simple_Schedule(void)
+{
+  _Thread_Heir = (Thread_Control *) _Chain_First( 
+    (Chain_Control *) _Scheduler.information 
+  );
+}
diff --git a/cpukit/score/src/schedulersimpleunblock.c b/cpukit/score/src/schedulersimpleunblock.c
new file mode 100644
index 0000000000..5be5c16ad9
--- /dev/null
+++ b/cpukit/score/src/schedulersimpleunblock.c
@@ -0,0 +1,47 @@
+/*
+ *  Scheduler Simple Handler / Unblock
+ *
+ *  COPYRIGHT (c) 2011.
+ *  On-Line Applications Research Corporation (OAR).
+ *
+ *  The license and distribution terms for this file may be
+ *  found in 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/isr.h>
+#include <rtems/score/schedulersimple.h>
+#include <rtems/score/thread.h>
+
+void _Scheduler_simple_Unblock(
+  Thread_Control    *the_thread
+)
+{
+  _Scheduler_simple_Ready_queue_Enqueue(the_thread);
+
+  /*
+   *  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 ( 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;
+  }
+}
diff --git a/cpukit/score/src/schedulersimpleyield.c b/cpukit/score/src/schedulersimpleyield.c
new file mode 100644
index 0000000000..61e80db7e2
--- /dev/null
+++ b/cpukit/score/src/schedulersimpleyield.c
@@ -0,0 +1,42 @@
+/*
+ *  Scheduler Simple Handler / Yield
+ *
+ *  COPYRIGHT (c) 2011.
+ *  On-Line Applications Research Corporation (OAR).
+ *
+ *  The license and distribution terms for this file may be
+ *  found in 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/isr.h>
+#include <rtems/score/scheduler.h>
+#include <rtems/score/thread.h>
+#include <rtems/score/schedulersimple.h>
+
+void _Scheduler_simple_Yield( void )
+{
+  ISR_Level       level;
+  Thread_Control *executing;
+
+  executing = _Thread_Executing;
+  _ISR_Disable( level );
+      
+    _Scheduler_simple_Ready_queue_Requeue(&_Scheduler, executing);
+
+    _ISR_Flash( level );
+
+    _Scheduler_simple_Schedule();
+    
+    if ( !_Thread_Is_heir( executing ) )
+      _Thread_Dispatch_necessary = true;
+
+  _ISR_Enable( level );
+}