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

//

//      sync/cnt_sem2.cxx

//

//      Counting semaphore implementation

//

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

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

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

//

// Author(s):   nickg

// Contributors:        nickg

// Date:        1997-09-24

// Purpose:     Cyg_Counting_Semaphore implementation

// Description: This file contains the implementations of the counting semaphore

//              class.

//

//####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/thread.inl>       // Cyg_Thread inlines

#include <cyg/kernel/sema2.hxx>        // our header

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

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

// Constructor

Cyg_Counting_Semaphore2::Cyg_Counting_Semaphore2(

    cyg_count32 init_count              // Initial count value

    )

{

    count       = init_count;

}

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

// Destructor

Cyg_Counting_Semaphore2::~Cyg_Counting_Semaphore2()

{

    CYG_REPORT_FUNCTION();

#if 0

    CYG_ASSERT( queue.empty(), "Destroying semaphore with waiting threads");

#endif

    // Prevent preemption

    Cyg_Scheduler::lock();

    while ( ! queue.empty() ) {

        Cyg_Thread *thread = queue.dequeue();

        thread->set_wake_reason( Cyg_Thread::DESTRUCT );

        thread->wake();

    }

    // Unlock the scheduler and maybe switch threads

    Cyg_Scheduler::unlock();

    CYG_REPORT_RETURN();

}

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

// Wait until the count can be decremented without it becoming

// negative.

cyg_bool Cyg_Counting_Semaphore2::wait()

{

    CYG_REPORT_FUNCTION();

    Cyg_Thread *self = Cyg_Thread::self();

    cyg_bool result = true;

    // Prevent preemption

    Cyg_Scheduler::lock();

    CYG_INSTRUMENT_CNTSEM( CLAIM, this, count );

    if ( 0 < count ) {

        count--;

        Cyg_Scheduler::unlock();

    }

    else {

        self->set_sleep_reason( Cyg_Thread::WAIT );

        self->sleep();

        queue.enqueue( self );

        CYG_INSTRUMENT_CNTSEM( WAIT, this, 0 );

        Cyg_Scheduler::unlock();

        CYG_INSTRUMENT_CNTSEM( WOKE, this, count );

        switch( self->get_wake_reason() )

        {

        case Cyg_Thread::DESTRUCT:

        case Cyg_Thread::BREAK:

            result = false;

            break;

        case Cyg_Thread::EXIT:

            self->exit();

            break;

        default:

            break;

        }

    }

    CYG_REPORT_RETVAL( result );

    return result;

}

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

// Wait until the count can be decremented without it becoming

// negative.

#ifdef CYGFUN_KERNEL_THREADS_TIMER

cyg_bool

Cyg_Counting_Semaphore2::wait( cyg_tick_count abs_timeout )

{

    CYG_REPORT_FUNCTION();

    Cyg_Thread *self = Cyg_Thread::self();

    cyg_bool result = true;

    // Prevent preemption

    Cyg_Scheduler::lock();

    CYG_INSTRUMENT_CNTSEM( CLAIM, this, count );

    if ( 0 < count ) {

        count--;

        Cyg_Scheduler::unlock();

    }

    else {

        // Put thread in sleep state before setting timer since if the

        // timeout is in the past, it will be re-awoken

        // immediately. If this happens then wake_reason will not be

        // NONE.

        self->sleep();

        self->set_timer( abs_timeout, Cyg_Thread::TIMEOUT );

        // only enqueue if the timeout did not already happen

        if( Cyg_Thread::NONE == self->get_wake_reason() )

            queue.enqueue( self );

        CYG_INSTRUMENT_CNTSEM( WAIT, this, 0 );

        Cyg_Scheduler::unlock();

        // Clear the timeout. It is irrelevant whether the alarm has

        // actually gone off or not.

        self->clear_timer();

        CYG_INSTRUMENT_CNTSEM( WOKE, this, count );

        switch( self->get_wake_reason() )

        {

        case Cyg_Thread::TIMEOUT:

            result = false;

            CYG_INSTRUMENT_CNTSEM( TIMEOUT, this, count);

            break;

        case Cyg_Thread::DESTRUCT:

        case Cyg_Thread::BREAK:

            result = false;

            break;

        case Cyg_Thread::EXIT:

            self->exit();

            break;

        default:

            break;

        }

    }

    CYG_REPORT_RETVAL( result );

    return result;

}

#endif // CYGFUN_KERNEL_THREADS_TIMER

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

// Try to decrement, but fail if not possible

cyg_bool Cyg_Counting_Semaphore2::trywait()

{

    CYG_REPORT_FUNCTION();

    cyg_bool result = true;

    // Prevent preemption

    Cyg_Scheduler::lock();

    if( 0 < count ) count--;

    else            result = false;

    CYG_INSTRUMENT_CNTSEM( TRY, this, result );

    // Unlock the scheduler and maybe switch threads

    Cyg_Scheduler::unlock();

    CYG_REPORT_RETVAL( result );

    return result;

}

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

// Increment count

void Cyg_Counting_Semaphore2::post()

{

    CYG_REPORT_FUNCTION();

    // Prevent preemption

    Cyg_Scheduler::lock();

    CYG_INSTRUMENT_CNTSEM( POST, this, 0 );

    if( queue.empty() ) {

        count++;

    }

    else {

        // The queue is non-empty, so grab the next

        // thread from it and wake it up. The waiter

        // won't decrement the count when he is awakened,

        // for we never incremented it in the first place

        Cyg_Thread *thread = queue.dequeue();

        thread->set_wake_reason( Cyg_Thread::DONE );

        thread->wake();

        CYG_INSTRUMENT_CNTSEM( WAKE, this, thread );

    }

    // Unlock the scheduler and maybe switch threads

    Cyg_Scheduler::unlock();

    CYG_REPORT_RETURN();

}

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

// Get current count value

cyg_count32 Cyg_Counting_Semaphore2::peek() const

{

    // This is a single read of the value of count.

    // This is already atomic, hence there is no need

    // to lock the scheduler.

    return count;

}

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

// EOF sync/cnt_sem2.cxx