sched.cxx

ecos实时嵌入式操作系统

    set_current_thread(next);           // restore current thread pointer

#ifdef CYGVAR_KERNEL_COUNTERS_CLOCK
    // Reference the real time clock. This ensures that at least one
    // reference to the kernel_clock.o object exists, without which
    // the object will not be included while linking.
    CYG_REFERENCE_OBJECT( Cyg_Clock::real_time_clock );
#endif

    // Load the first thread. This will also enable interrupts since
    // the initial state of all threads is to have interrupts enabled.
    
    HAL_THREAD_LOAD_CONTEXT( &next->stack_ptr );    
    
}

// -------------------------------------------------------------------------
// SMP support functions

#ifdef CYGPKG_KERNEL_SMP_SUPPORT

// This is called on each secondary CPU on its interrupt stack after
// the initial CPU has initialized the world.

externC void cyg_kernel_smp_startup()
{
    CYG_INSTRUMENT_SMP( CPU_START, CYG_KERNEL_CPU_THIS(), 0 );
    Cyg_Scheduler::lock();
    Cyg_Scheduler::start_cpu();
}

// This is called from the DSR of the inter-CPU interrupt to cause a
// reschedule when the scheduler lock is zeroed.

__externC void cyg_scheduler_set_need_reschedule()
{
    CYG_INSTRUMENT_SMP( RESCHED_RECV, 0, 0 );    
    Cyg_Scheduler::need_reschedule[HAL_SMP_CPU_THIS()] = true;
}

#endif

// -------------------------------------------------------------------------
// Consistency checker

#ifdef CYGDBG_USE_ASSERTS

cyg_bool Cyg_Scheduler::check_this( cyg_assert_class_zeal zeal) const
{
    CYG_REPORT_FUNCTION();
        
    // check that we have a non-NULL pointer first
    if( this == NULL ) return false;
    
    switch( zeal )
    {
    case cyg_system_test:
    case cyg_extreme:
    case cyg_thorough:
        if( !get_current_thread()->check_this(zeal) ) return false;
    case cyg_quick:
    case cyg_trivial:
    case cyg_none:
    default:
        break;
    };

    return true;
}

#endif

//==========================================================================
// SchedThread members

// -------------------------------------------------------------------------
// Static data members

#ifdef CYGSEM_KERNEL_SCHED_ASR_SUPPORT

# ifdef CYGSEM_KERNEL_SCHED_ASR_GLOBAL
Cyg_ASR *Cyg_SchedThread::asr = &Cyg_SchedThread::asr_default;
# endif

# ifdef CYGSEM_KERNEL_SCHED_ASR_DATA_GLOBAL
CYG_ADDRWORD Cyg_SchedThread::asr_data = 0;
# endif

#endif // CYGSEM_KERNEL_SCHED_ASR_SUPPORT

// -------------------------------------------------------------------------
// Constructor

Cyg_SchedThread::Cyg_SchedThread(Cyg_Thread *thread, CYG_ADDRWORD sched_info)
: Cyg_SchedThread_Implementation(sched_info)
{
    CYG_REPORT_FUNCTION();
        
    queue = NULL;

#ifdef CYGSEM_KERNEL_SYNCH_MUTEX_PRIORITY_INVERSION_PROTOCOL

    mutex_count = 0;
    
#ifdef CYGSEM_KERNEL_SYNCH_MUTEX_PRIORITY_INVERSION_PROTOCOL_SIMPLE
    
    priority_inherited = false;
    
#endif
#endif

#ifdef CYGSEM_KERNEL_SCHED_ASR_SUPPORT

    asr_inhibit = 0;
    asr_pending = false;

#ifndef CYGSEM_KERNEL_SCHED_ASR_GLOBAL
    asr = asr_default;
#endif
#ifdef CYGSEM_KERNEL_SCHED_ASR_DATA_GLOBAL
    asr_data = NULL
#endif        
    
#endif    
}

// -------------------------------------------------------------------------
// ASR support functions

#ifdef CYGSEM_KERNEL_SCHED_ASR_SUPPORT

// -------------------------------------------------------------------------
// Set ASR
// Install a new ASR, returning the old one.

void Cyg_SchedThread::set_asr( Cyg_ASR  *new_asr, CYG_ADDRWORD  new_data,
                  Cyg_ASR **old_asr, CYG_ADDRWORD *old_data)
{
    CYG_REPORT_FUNCTION();

    // Do this with the scheduler locked...
    Cyg_Scheduler::lock();

    if( old_asr != NULL ) *old_asr = asr;
    if( old_data != NULL ) *old_data = asr_data;

    // If new_asr is NULL, do not change the ASR,
    // but only change the data.
    if( new_asr != NULL ) asr = new_asr;
    asr_data = new_data;
    
    Cyg_Scheduler::unlock();
}

// -------------------------------------------------------------------------
// Clear ASR

void Cyg_SchedThread::clear_asr()
{
    CYG_REPORT_FUNCTION();

    // Do this with the scheduler locked...
    Cyg_Scheduler::lock();

    // Reset ASR to default.
    asr = asr_default;
    asr_data = 0;
    
    Cyg_Scheduler::unlock();    
}

// -------------------------------------------------------------------------
// Default ASR function.
// having this avoids our having to worry about ever seeing a NULL
// pointer as the ASR function.

void Cyg_SchedThread::asr_default(CYG_ADDRWORD data)
{
    CYG_REPORT_FUNCTION();

    data=data;
    return;
}

#endif

// -------------------------------------------------------------------------
// Generic priority protocol support

#ifdef CYGSEM_KERNEL_SYNCH_MUTEX_PRIORITY_INVERSION_PROTOCOL

void Cyg_SchedThread::set_inherited_priority( cyg_priority pri, Cyg_Thread *thread )
{
    CYG_REPORT_FUNCTION();

#ifdef CYGSEM_KERNEL_SYNCH_MUTEX_PRIORITY_INVERSION_PROTOCOL_SIMPLE

    // This is the comon code for priority inheritance and ceiling
    // protocols. This implementation provides a simplified version of
    // the protocol.
    
    Cyg_Thread *self = CYG_CLASSFROMBASE(Cyg_Thread,
                                         Cyg_SchedThread,
                                         this);

    CYG_ASSERT( mutex_count > 0, "Non-positive mutex count");
    
    // Compare with *current* priority in case thread has already
    // inherited - for relay case below.
    if( pri < priority )
    {
        cyg_priority mypri = priority;
        cyg_bool already_inherited = priority_inherited;

        // If this is first inheritance, copy the old pri
        // and set inherited flag. We clear it before setting the
        // pri since set_priority() is inheritance aware.
        // This is called with the sched locked, so no race conditions.

        priority_inherited = false;     // so that set_prio DTRT

        self->set_priority( pri );            

        if( !already_inherited )
            original_priority = mypri;

        priority_inherited = true;      // regardless, because it is now

    }

#endif
}

void Cyg_SchedThread::relay_inherited_priority( Cyg_Thread *ex_owner, Cyg_ThreadQueue *pqueue)
{
    CYG_REPORT_FUNCTION();

#ifdef CYGSEM_KERNEL_SYNCH_MUTEX_PRIORITY_INVERSION_PROTOCOL_SIMPLE

    // A simple implementation of priority inheritance.
    // At its simplest, this member does nothing.

    // If there is anyone else waiting, then the *new* owner inherits from
    // the current one, since that is a maxima of the others waiting.
    // (It's worth not doing if there's nobody waiting to prevent
    // unneccessary priority skew.)  This could be viewed as a discovered
    // priority ceiling.

    if ( !pqueue->empty() )
        set_inherited_priority( ex_owner->get_current_priority(), ex_owner );

#endif
}

void Cyg_SchedThread::clear_inherited_priority()
{
    CYG_REPORT_FUNCTION();

#ifdef CYGSEM_KERNEL_SYNCH_MUTEX_PRIORITY_INVERSION_PROTOCOL_SIMPLE

    // A simple implementation of priority inheritance/ceiling
    // protocols.  The simplification in this algorithm is that we do
    // not reduce our priority until we have freed all mutexes
    // claimed. Hence we can continue to run at an artificially high
    // priority even when we should not.  However, since nested
    // mutexes are rare, the thread we have inherited from is likely
    // to be locking the same mutexes we are, and mutex claim periods
    // should be very short, the performance difference between this
    // and a more complex algorithm should be negligible. The most
    // important advantage of this algorithm is that it is fast and
    // deterministic.
    
    Cyg_Thread *self = CYG_CLASSFROMBASE(Cyg_Thread,
                                         Cyg_SchedThread,
                                         this);

    CYG_ASSERT( mutex_count >= 0, "Non-positive mutex count");
    
    if( mutex_count == 0 && priority_inherited )
    {
        priority_inherited = false;

        // Only make an effort if the priority must change
        if( priority < original_priority )
            self->set_priority( original_priority );
        
    }
    
#endif        
}

#endif // CYGSEM_KERNEL_SYNCH_MUTEX_PRIORITY_INVERSION_PROTOCOL

// -------------------------------------------------------------------------
// Priority inheritance support.

#ifdef CYGSEM_KERNEL_SYNCH_MUTEX_PRIORITY_INVERSION_PROTOCOL_INHERIT

// -------------------------------------------------------------------------
// Inherit the priority of the provided thread if it
// has a higher priority than ours.

void Cyg_SchedThread::inherit_priority( Cyg_Thread *thread)
{
    CYG_REPORT_FUNCTION();

    Cyg_Thread *self = CYG_CLASSFROMBASE(Cyg_Thread,
                                         Cyg_SchedThread,
                                         this);

    CYG_ASSERT( mutex_count > 0, "Non-positive mutex count");
    CYG_ASSERT( self != thread, "Trying to inherit from self!");

    self->set_inherited_priority( thread->get_current_priority(), thread );
    
}

// -------------------------------------------------------------------------
// Inherit the priority of the ex-owner thread or from the queue if it
// has a higher priority than ours.

void Cyg_SchedThread::relay_priority( Cyg_Thread *ex_owner, Cyg_ThreadQueue *pqueue)
{
    CYG_REPORT_FUNCTION();

    relay_inherited_priority( ex_owner, pqueue );
}

// -------------------------------------------------------------------------
// Lose a priority inheritance

void Cyg_SchedThread::disinherit_priority()
{
    CYG_REPORT_FUNCTION();

    CYG_ASSERT( mutex_count >= 0, "Non-positive mutex count");

    clear_inherited_priority();
}

#endif // CYGSEM_KERNEL_SYNCH_MUTEX_PRIORITY_INVERSION_PROTOCOL_INHERIT

// -------------------------------------------------------------------------
// Priority ceiling support

#ifdef CYGSEM_KERNEL_SYNCH_MUTEX_PRIORITY_INVERSION_PROTOCOL_CEILING

void Cyg_SchedThread::set_priority_ceiling( cyg_priority pri )
{
    CYG_REPORT_FUNCTION();

    CYG_ASSERT( mutex_count > 0, "Non-positive mutex count");

    set_inherited_priority( pri );

}

void Cyg_SchedThread::clear_priority_ceiling( )
{
    CYG_REPORT_FUNCTION();

    CYG_ASSERT( mutex_count >= 0, "Non-positive mutex count");

    clear_inherited_priority();
}

#endif // CYGSEM_KERNEL_SYNCH_MUTEX_PRIORITY_INVERSION_PROTOCOL_CEILING

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