mlqueue.cxx

eCos1.31版

    CYG_REPORT_FUNCTION();
    CYG_REPORT_FUNCARG1("sched_info=%08x", sched_info);
        
    // Create all threads at maximum priority
    priority = (cyg_priority)sched_info;

    // point the next and prev field at this thread.
    
    next = prev = CYG_CLASSFROMBASE(Cyg_Thread,
                                    Cyg_SchedThread_Implementation,
                                    this);
    CYG_REPORT_RETURN();
}

// -------------------------------------------------------------------------
// Insert thread in front of this

void
Cyg_SchedThread_Implementation::insert( Cyg_Thread *thread)
{
    CYG_REPORT_FUNCTION();
    CYG_REPORT_FUNCARG1("thread=%08x", thread);
        
    thread->next        = CYG_CLASSFROMBASE(Cyg_Thread,
                                            Cyg_SchedThread_Implementation,
                                            this);
    thread->prev        = prev;
    prev->next          = thread;
    prev                = thread;    

    CYG_REPORT_RETURN();
}

// -------------------------------------------------------------------------
// remove this from queue

void
Cyg_SchedThread_Implementation::remove(void)
{
    CYG_REPORT_FUNCTION();
        
    next->prev          = prev;
    prev->next          = next;
    next = prev         = CYG_CLASSFROMBASE(Cyg_Thread,
                                            Cyg_SchedThread_Implementation,
                                            this);
    CYG_REPORT_RETURN();
}

// -------------------------------------------------------------------------
// Yield the processor to another thread

void
Cyg_SchedThread_Implementation::yield(void)
{
    CYG_REPORT_FUNCTION();
        
    // Prevent preemption
    Cyg_Scheduler::lock();

    Cyg_Thread *thread  = CYG_CLASSFROMBASE(Cyg_Thread,
                                            Cyg_SchedThread_Implementation,
                                            this);

    // Only do this if this thread is running. If it is not, there
    // is no point.
    
    if( thread->get_state() == Cyg_Thread::RUNNING )
    {
        // To yield we simply rotate the appropriate
        // run queue to the next thread and reschedule.

        CYG_ASSERTCLASS( thread, "Bad current thread");
    
        Cyg_Scheduler *sched = &Cyg_Scheduler::scheduler;

        CYG_ASSERTCLASS( sched, "Bad scheduler");
    
        cyg_priority pri                            = thread->priority;
        Cyg_ThreadQueue_Implementation *queue       = &sched->run_queue[pri];

        queue->rotate();

        if( queue->highpri() != thread )
            sched->need_reschedule = true;
#ifdef CYGSEM_KERNEL_SCHED_TIMESLICE
            // Reset the timeslice counter so that this thread gets a full
            // quantum. 
        else Cyg_Scheduler::reset_timeslice_count();
#endif
    }
    
    // Unlock the scheduler and switch threads
    Cyg_Scheduler::unlock();

    CYG_REPORT_RETURN();
}

// -------------------------------------------------------------------------
// Rotate the run queue at a specified priority.
// (pri is the decider, no this, so the routine is static)

void
Cyg_SchedThread_Implementation::rotate_queue( cyg_priority pri )
{
    CYG_REPORT_FUNCTION();
    CYG_REPORT_FUNCARG1("priority=%d", pri);
        
    // Prevent preemption
    Cyg_Scheduler::lock();

    Cyg_Scheduler *sched = &Cyg_Scheduler::scheduler;

    CYG_ASSERTCLASS( sched, "Bad scheduler");
    
    Cyg_ThreadQueue_Implementation *queue = &sched->run_queue[pri];

    if ( !queue->empty() ) {
        queue->rotate();
        sched->need_reschedule = true;
    }

    // Unlock the scheduler and switch threads
    Cyg_Scheduler::unlock();

    CYG_REPORT_RETURN();
}

// -------------------------------------------------------------------------
// Move this thread to the head of its queue
// (not necessarily a scheduler queue)

void
Cyg_SchedThread_Implementation::to_queue_head( void )
{
    CYG_REPORT_FUNCTION();
        
    // Prevent preemption
    Cyg_Scheduler::lock();

    Cyg_Thread *thread  = CYG_CLASSFROMBASE(Cyg_Thread,
                                            Cyg_SchedThread_Implementation,
                                            this);

    CYG_ASSERTCLASS( thread, "Bad current thread");
    
    Cyg_ThreadQueue *q = thread->get_current_queue();
    q->to_head( thread );

    // Unlock the scheduler and switch threads
    Cyg_Scheduler::unlock();

    CYG_REPORT_RETURN();
}

//==========================================================================
// Cyg_ThreadQueue_Implementation class members

Cyg_ThreadQueue_Implementation::Cyg_ThreadQueue_Implementation()
{
    CYG_REPORT_FUNCTION();
        
    queue = NULL;                       // empty queue

    CYG_REPORT_RETURN();
}

        

void
Cyg_ThreadQueue_Implementation::enqueue(Cyg_Thread *thread)
{
    CYG_REPORT_FUNCTION();
    CYG_REPORT_FUNCARG1("thread=%08x", thread);

    if( queue == NULL ) queue = thread;
    else queue->insert(thread);
    
    thread->queue = CYG_CLASSFROMBASE(Cyg_ThreadQueue,
                                      Cyg_ThreadQueue_Implementation,
                                      this);
    CYG_REPORT_RETURN();
}

// -------------------------------------------------------------------------

Cyg_Thread *
Cyg_ThreadQueue_Implementation::dequeue(void)
{
    CYG_REPORT_FUNCTYPE("returning thread %08x");
        
    if( queue == NULL ) {
        CYG_REPORT_RETVAL(NULL);
        return NULL;
    }
    
    Cyg_Thread *thread = queue;
    
    if( thread->next == thread )
    {
        // sole thread on list, NULL out ptr
        queue = NULL;
    }
    else
    {
        // advance to next and remove thread
        queue = thread->next;
        thread->remove();
    }

    thread->queue = NULL;

    CYG_REPORT_RETVAL(thread);
    return thread;
}

// -------------------------------------------------------------------------

Cyg_Thread *
Cyg_ThreadQueue_Implementation::highpri(void)
{
    CYG_REPORT_FUNCTYPE("returning thread %08x");
    CYG_REPORT_RETVAL(queue);
    return queue;
}

// -------------------------------------------------------------------------

void
Cyg_ThreadQueue_Implementation::remove(Cyg_Thread *thread)
{
    CYG_REPORT_FUNCTION();
    CYG_REPORT_FUNCARG1("thread=%08x", thread);
        
    // If the thread we want it the at the head
    // of the list, and is on its own, clear the
    // list and return. Otherwise advance to the
    // next thread and remove ours. If the thread
    // is not at the head of the list, just dequeue
    // it.

    thread->queue = NULL;
    
    if( queue == thread )
    {
        if( thread->next == thread )
        {
            queue = NULL;
            return;
        }
        else queue = thread->next;
    }

    thread->Cyg_SchedThread_Implementation::remove();

    CYG_REPORT_RETURN();
}

// -------------------------------------------------------------------------
// Rotate the front thread on the queue to the back.

void
Cyg_ThreadQueue_Implementation::rotate(void)
{
    CYG_REPORT_FUNCTION();
        
    queue = queue->next;

    CYG_REPORT_RETURN();
}

// -------------------------------------------------------------------------
// Rotate or move the thread quoted to the front.

void
Cyg_ThreadQueue_Implementation::to_head(Cyg_Thread *thread)
{
    CYG_REPORT_FUNCTION();
        
    queue = thread;

    CYG_REPORT_RETURN();
}

// -------------------------------------------------------------------------

#endif

// -------------------------------------------------------------------------
// EOF sched/mlqueue.cxx