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//==========================================================================

//

//      sched/sched.cxx

//

//      Scheduler class implementations

//

//==========================================================================

// ####ECOSGPLCOPYRIGHTBEGIN####                                            

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//

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//

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//

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// ####ECOSGPLCOPYRIGHTEND####                                              

//==========================================================================

//#####DESCRIPTIONBEGIN####

//

// Author(s):   nickg

// Contributors:        nickg

// Date:        1997-09-15

// Purpose:     Scheduler class implementation

// Description: This file contains the definitions of the scheduler class

//              member functions that are common to all scheduler

//              implementations.

//

//####DESCRIPTIONEND####

//

//==========================================================================

#include <pkgconf/kernel.h>

#include <cyg/kernel/ktypes.h>         // base kernel types

#include <cyg/infra/cyg_trac.h>        // tracing macros

#include <cyg/infra/cyg_ass.h>         // assertion macros

#include <cyg/kernel/instrmnt.h>       // instrumentation

#include <cyg/kernel/sched.hxx>        // our header

#include <cyg/kernel/thread.hxx>       // thread classes

#include <cyg/kernel/intr.hxx>         // Interrupt interface

#include <cyg/hal/hal_arch.h>          // Architecture specific definitions

#include <cyg/kernel/thread.inl>       // thread inlines

#include <cyg/kernel/sched.inl>        // scheduler inlines

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

// Some local tracing control - a default.

#ifdef CYGDBG_USE_TRACING

# if !defined( CYGDBG_INFRA_DEBUG_TRACE_ASSERT_SIMPLE ) && \

     !defined( CYGDBG_INFRA_DEBUG_TRACE_ASSERT_FANCY  )

   // ie. not a tracing implementation that takes a long time to output

#  ifndef CYGDBG_KERNEL_TRACE_UNLOCK_INNER

#   define CYGDBG_KERNEL_TRACE_UNLOCK_INNER

#  endif // control not already defined

# endif  // trace implementation not ..._SIMPLE && not ..._FANCY

#endif   // CYGDBG_USE_TRACING

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

// Static Cyg_Scheduler class members

// We start with sched_lock at 1 so that any kernel code we

// call during initialization will not try to reschedule.

CYGIMP_KERNEL_SCHED_LOCK_DEFINITIONS;

Cyg_Thread              *volatile Cyg_Scheduler_Base::current_thread[CYGNUM_KERNEL_CPU_MAX];

volatile cyg_bool       Cyg_Scheduler_Base::need_reschedule[CYGNUM_KERNEL_CPU_MAX];

Cyg_Scheduler           Cyg_Scheduler::scheduler CYG_INIT_PRIORITY( SCHEDULER );

volatile cyg_ucount32   Cyg_Scheduler_Base::thread_switches[CYGNUM_KERNEL_CPU_MAX];

#ifdef CYGPKG_KERNEL_SMP_SUPPORT

CYG_BYTE cyg_sched_cpu_interrupt[CYGNUM_KERNEL_CPU_MAX][sizeof(Cyg_Interrupt)]

                                 CYGBLD_ANNOTATE_VARIABLE_SCHED;

__externC cyg_ISR cyg_hal_cpu_message_isr;

__externC cyg_DSR cyg_hal_cpu_message_dsr;

inline void *operator new(size_t size, void *ptr) { return ptr; };

#endif

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

// Scheduler unlock function.

// This is only called when there is the potential for real work to be

// done. Other cases are handled in Cyg_Scheduler::unlock() which is

// an inline; _or_ this function may have been called from

// Cyg_Scheduler::reschedule(), or Cyg_Scheduler::unlock_reschedule. The

// new_lock argument contains the value that the scheduler lock should

// have after this function has completed. If it is zero then the lock is

// being released and some extra work (running ASRs, checking for DSRs) is

// done before returning. If it is non-zero then it must equal the

// current value of the lock, and is used to indicate that we want to

// reacquire the scheduler lock before returning. This latter option

// only makes any sense if the current thread is no longer runnable,

// e.g. sleeping, otherwise this function will do nothing.

// This approach of passing in the lock value at the end effectively

// makes the scheduler lock a form of per-thread variable. Each call

// to unlock_inner() carries with it the value the scheduler should

// have when it reschedules this thread back, and leaves this function.

// When it is non-zero, and the thread is rescheduled, no ASRS are run,

// or DSRs processed. By doing this, it makes it possible for threads

// that want to go to sleep to wake up with the scheduler lock in the

// same state it was in before.

void Cyg_Scheduler::unlock_inner( cyg_ucount32 new_lock )

{

#ifdef CYGDBG_KERNEL_TRACE_UNLOCK_INNER

    CYG_REPORT_FUNCTION();

#endif    

    do {

        CYG_PRECONDITION( new_lock==0 ? get_sched_lock() == 1 :

                          ((get_sched_lock() == new_lock) || (get_sched_lock() == new_lock+1)),

                          "sched_lock not at expected value" );

#ifdef CYGIMP_KERNEL_INTERRUPTS_DSRS

        // Call any pending DSRs. Do this here to ensure that any

        // threads that get awakened are properly scheduled.

        if( new_lock == 0 && Cyg_Interrupt::DSRs_pending() )

            Cyg_Interrupt::call_pending_DSRs();

#endif

        Cyg_Thread *current = get_current_thread();

        CYG_ASSERTCLASS( current, "Bad current thread" );

#ifdef CYGFUN_KERNEL_ALL_THREADS_STACK_CHECKING

        // should have  CYGVAR_KERNEL_THREADS_LIST

        current = Cyg_Thread::get_list_head();

        while ( current ) {

            current->check_stack();

            current = current->get_list_next();

        }

        current = get_current_thread();

#endif

#ifdef CYGFUN_KERNEL_THREADS_STACK_CHECKING

        current->check_stack();

#endif

        // If the current thread is going to sleep, or someone

        // wants a reschedule, choose another thread to run

        if( current->state != Cyg_Thread::RUNNING || get_need_reschedule() ) {

            CYG_INSTRUMENT_SCHED(RESCHEDULE,0,0);

            // Get the next thread to run from scheduler

            Cyg_Thread *next = scheduler.schedule();

            CYG_CHECK_DATA_PTR( next, "Invalid next thread pointer");

            CYG_ASSERTCLASS( next, "Bad next thread" );

            if( current != next )

            {

                CYG_INSTRUMENT_THREAD(SWITCH,current,next);

                // Count this thread switch

                thread_switches[CYG_KERNEL_CPU_THIS()]++;

#ifdef CYGFUN_KERNEL_THREADS_STACK_CHECKING

                next->check_stack(); // before running it

#endif

                current->timeslice_save();

                // Switch contexts

                HAL_THREAD_SWITCH_CONTEXT( &current->stack_ptr,

                                           &next->stack_ptr );

                // Worry here about possible compiler

                // optimizations across the above call that may try to

                // propogate common subexpresions.  We would end up

                // with the expression from one thread in its

                // successor. This is only a worry if we do not save

                // and restore the complete register set. We need a

                // way of marking functions that return into a

                // different context. A temporary fix would be to

                // disable CSE (-fdisable-cse) in the compiler.

                // We return here only when the current thread is

                // rescheduled.  There is a bit of housekeeping to do

                // here before we are allowed to go on our way.

                CYG_CHECK_DATA_PTR( current, "Invalid current thread pointer");

                CYG_ASSERTCLASS( current, "Bad current thread" );

                current_thread[CYG_KERNEL_CPU_THIS()] = current;   // restore current thread pointer

                current->timeslice_restore();

            }

            clear_need_reschedule();    // finished rescheduling

        }

        if( new_lock == 0 )

        {

#ifdef CYGSEM_KERNEL_SCHED_ASR_SUPPORT

            // Check whether the ASR is pending and not inhibited.  If

            // we can call it, then transfer this info to a local

            // variable (call_asr) and clear the pending flag.  Note

            // that we only do this if the scheduler lock is about to

            // be zeroed. In any other circumstance we are not

            // unlocking.

            cyg_bool call_asr = false;

            if( (current->asr_inhibit == 0) && current->asr_pending )

            {

                call_asr = true;

                current->asr_pending = false;

            }

#endif

            HAL_REORDER_BARRIER(); // Make sure everything above has happened

                                   // by this point

            zero_sched_lock();     // Clear the lock

            HAL_REORDER_BARRIER();

#ifdef CYGIMP_KERNEL_INTERRUPTS_DSRS

            // Now check whether any DSRs got posted during the thread

            // switch and if so, go around again. Making this test after

            // the lock has been zeroed avoids a race condition in which

            // a DSR could have been posted during a reschedule, but would

            // not be run until the _next_ time we release the sched lock.

            if( Cyg_Interrupt::DSRs_pending() ) {

                inc_sched_lock();   // reclaim the lock

                continue;           // go back to head of loop

            }

#endif

            // Otherwise the lock is zero, we can return.

//            CYG_POSTCONDITION( get_sched_lock() == 0, "sched_lock not zero" );

#ifdef CYGSEM_KERNEL_SCHED_ASR_SUPPORT

            // If the test within the sched_lock indicating that the ASR

            // be called was true, call it here. Calling the ASR must be

            // the very last thing we do here, since it must run as close

            // to "user" state as possible.

            if( call_asr ) current->asr(current->asr_data);

#endif

        }

        else

        {

            // If new_lock is non-zero then we restore the sched_lock to

            // the value given.

            HAL_REORDER_BARRIER();

            set_sched_lock(new_lock);

            HAL_REORDER_BARRIER();

        }

#ifdef CYGDBG_KERNEL_TRACE_UNLOCK_INNER

        CYG_REPORT_RETURN();

#endif

        return;

    } while( 1 );

    CYG_FAIL( "Should not be executed" );

}

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

// Thread startup. This is called from Cyg_Thread::thread_entry() and

// performs some housekeeping for a newly started thread.

void Cyg_Scheduler::thread_entry( Cyg_Thread *thread )

{

    clear_need_reschedule();            // finished rescheduling

    set_current_thread(thread);         // restore current thread pointer

    CYG_INSTRUMENT_THREAD(ENTER,thread,0);

    thread->timeslice_reset();

    thread->timeslice_restore();

    // Finally unlock the scheduler. As well as clearing the scheduler

    // lock this allows any pending DSRs to execute. The new thread

    // must start with a lock of zero, so we keep unlocking until the

    // lock reaches zero.

    while( get_sched_lock() != 0 )

        unlock();

}

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

// Start the scheduler. This is called after the initial threads have been

// created to start scheduling. It gets any other CPUs running, and then

// enters the scheduler.

void Cyg_Scheduler::start()

{

    CYG_REPORT_FUNCTION();

#ifdef CYGPKG_KERNEL_SMP_SUPPORT

    HAL_SMP_CPU_TYPE cpu;

    for( cpu = 0; cpu < CYG_KERNEL_CPU_COUNT(); cpu++ )

    {

        // Don't start this CPU, it is running already!

        if( cpu == CYG_KERNEL_CPU_THIS() )

            continue;

        CYG_KERNEL_CPU_START( cpu );

    }

#endif    

    start_cpu();

}

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

// Start scheduling on this CPU. This is called on each CPU in the system

// when it is started.

void Cyg_Scheduler::start_cpu()

{

    CYG_REPORT_FUNCTION();

#ifdef CYGPKG_KERNEL_SMP_SUPPORT

    // Set up the inter-CPU interrupt for this CPU

    Cyg_Interrupt * intr = new( (void *)&cyg_sched_cpu_interrupt[HAL_SMP_CPU_THIS()] )

        Cyg_Interrupt( CYGNUM_HAL_SMP_CPU_INTERRUPT_VECTOR( HAL_SMP_CPU_THIS() ),

                       0,

                       0,

                       cyg_hal_cpu_message_isr,

                       cyg_hal_cpu_message_dsr

                     );

    intr->set_cpu( intr->get_vector(), HAL_SMP_CPU_THIS() );

    intr->attach();

    intr->unmask_interrupt( intr->get_vector() );

#endif    

    // Get the first thread to run from scheduler

    register Cyg_Thread *next = scheduler.schedule();

    CYG_ASSERTCLASS( next, "Bad initial thread" );

    clear_need_reschedule();            // finished rescheduling

    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