score: add Inherited_priorities priority queue and functions

Adds enqueue, dequeue, requeue, evaluate, and release functions
for the thread priority node priority queue of inherited priorities.
Add calls to these functions as needed to maintain the priority
queue due to blocking, unblocking, and priority changes.

Closes #3359.

1 files changed, 167 insertions, 0 deletions

diff --git a/cpukit/score/src/threadprioritynode.c b/cpukit/score/src/threadprioritynode.c
new file mode 100644
index 0000000000..69bbe14972
--- /dev/null
+++ b/cpukit/score/src/threadprioritynode.c
@@ -0,0 +1,167 @@
+/*
+ * Thread Priority Node
+ * 
+ * Copyright (C) 2017. Gedare Bloom.
+ *
+ * The license and distribution terms for this file may be
+ * found in the file LICENSE in this distribution or at
+ * http://www.rtems.org/license/LICENSE.
+ */
+
+#if HAVE_CONFIG_H
+#include "config.h"
+#endif
+
+#include <rtems/system.h>
+#include <rtems/config.h>
+#include <rtems/score/chain.h>
+#include <rtems/score/coremutex.h>
+#include <rtems/score/thread.h>
+
+/**
+ * This routine adds a thread's Priority_node to the mutex holder's
+ * Inherited_priorities list, and sets the waiting_to_hold field to the
+ * mutex.
+ *
+ * Returns true if the enqueued node is at the head of the holder's
+ * Inherited priorities, and therefore the holder's priority may change.
+ */
+bool _Thread_Enqueue_priority_node(
+  Thread_Control     *the_thread,
+  CORE_mutex_Control *the_mutex
+)
+{
+  Chain_Node *iter;
+  Thread_Priority_node *thread_pn, *holder_pn;
+  Priority_Control task_priority, iter_priority;
+  
+  thread_pn = &the_thread->Priority_node;
+  holder_pn = &the_mutex->holder->Priority_node;
+
+  thread_pn->waiting_to_hold = the_mutex;
+  iter = holder_pn->Inherited_priorities.first;
+  task_priority = thread_pn->current_priority;
+
+  /* Find the first node in holder's Inherited_priorities list with
+   * lower priority than the task, or find the end of the list. */
+  while ( !_Chain_Is_tail( &holder_pn->Inherited_priorities, iter) ) {
+    iter_priority = ((Thread_Priority_node *)iter)->current_priority;
+    if ( iter_priority > task_priority ) {
+      break;
+    }
+    iter = _Chain_Next( iter );
+  }
+  _Chain_Insert_unprotected( _Chain_Previous( iter ), &thread_pn->Node );
+
+  /* If the_thread is at the start of the holder's Inherited_priorites list,
+   * then may need to update the holder's current priority. */
+  if ( _Chain_Is_first( &thread_pn->Node ) ) {
+    return true;
+  }
+  return false;
+}
+
+/**
+ * This routine sets the thread's priority_node->current_priority to the
+ * minimum of the real_priority and the first node of Inherited_priorities,
+ * if any.
+ */
+void _Thread_Evaluate_priority(
+  Thread_Control *the_thread
+)
+{
+  Chain_Node *first;
+  Thread_Priority_node *first_pn, *priority_node;
+  Priority_Control current_priority, min_priority;
+
+  /* Start with the_thread, and iterate through the holder threads that
+   * the_thread is waiting on. If any thread's priority does not change,
+   * then stop iterating. */
+  while ( the_thread != NULL ) {
+    priority_node = &the_thread->Priority_node;
+    current_priority = priority_node->current_priority;
+    min_priority = priority_node->real_priority;
+    first = _Chain_First( &priority_node->Inherited_priorities );
+    if ( !_Chain_Is_tail( &priority_node->Inherited_priorities, first ) ) {
+      first_pn = (Thread_Priority_node *)first;
+      if ( min_priority > first_pn->current_priority ) {
+        min_priority = first_pn->current_priority;
+      }
+    }
+    if ( current_priority < min_priority ) {
+      _Thread_Change_priority( the_thread, min_priority, true );
+    } else if ( current_priority > min_priority ) {
+      _Thread_Change_priority( the_thread, min_priority, false );
+    } else {
+      break;
+    }
+    if ( the_thread->Priority_node.waiting_to_hold != NULL ) {
+      the_thread = the_thread->Priority_node.waiting_to_hold->holder;
+    } else {
+      the_thread = NULL;
+    }
+  }
+}
+
+/**
+ * This routine removes a thread's Priority_node from an
+ * Inherited_priorities list, updates the mutex holder's
+ * current_priority if needed, and clears the mutex field.
+ *
+ * Returns the mutex that the_thread was waiting on.
+ */
+CORE_mutex_Control* _Thread_Dequeue_priority_node(
+  Thread_Priority_node *thread_pn
+)
+{
+  CORE_mutex_Control *the_mutex = thread_pn->waiting_to_hold;
+
+  if ( the_mutex == NULL ) {
+    return NULL;
+  }
+
+  _Chain_Extract_unprotected( &thread_pn->Node );
+  thread_pn->waiting_to_hold = NULL;
+
+  return the_mutex;
+}
+
+void _Thread_Requeue_priority_node(
+  Thread_Control *the_thread
+)
+{
+  ISR_Level       level;
+  CORE_mutex_Control *mutex;
+  
+  _ISR_Disable( level );
+  /* TODO: refactor? */
+  mutex = _Thread_Dequeue_priority_node( &the_thread->Priority_node );
+  if ( mutex != NULL ) {
+    _Thread_Enqueue_priority_node( the_thread, mutex );
+  }
+  _ISR_Enable( level );
+}
+
+/**
+ * This routine removes the inherited priorities from the mutex being
+ * released and updates the holder's priority if necessary.
+ */
+void _Thread_Release_inherited_priority(
+  CORE_mutex_Control *the_mutex
+)
+{
+  Chain_Control *ip = &the_mutex->holder->Priority_node.Inherited_priorities;
+  Chain_Node *cn;
+  Thread_Priority_node *tpn;
+
+  for (cn = _Chain_First(ip); !_Chain_Is_tail(ip, cn); cn = _Chain_Next(cn)) {
+    tpn = (Thread_Priority_node*)cn;
+    if ( tpn->waiting_to_hold == the_mutex ) {
+      _Chain_Extract(cn);
+      tpn->waiting_to_hold = NULL;
+    }
+  }
+
+  _Thread_Evaluate_priority( the_mutex->holder );
+}
+