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/*
* 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 );
}
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