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

//

//        bin_sem2.cxx

//

//        Binary semaphore test 2

//

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

//####ECOSGPLCOPYRIGHTBEGIN####

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

// This file is part of eCos, the Embedded Configurable Operating System.

// Copyright (C) 1998, 1999, 2000, 2001, 2002 Red Hat, Inc.

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

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

//

// Author(s):     nickg,dsm

// Contributors:    dsm

// Date:          1998-03-10

// Description:

//     Dining philosophers test.  Based on philo.cxx

//####DESCRIPTIONEND####

#include <pkgconf/kernel.h>

#include <cyg/kernel/sched.hxx>

#include <cyg/kernel/thread.hxx>

#include <cyg/kernel/thread.inl>

#include <cyg/kernel/mutex.hxx>

#include <cyg/kernel/sema.hxx>

#include <cyg/infra/testcase.h>

#include <cyg/kernel/sched.inl>

static cyg_ucount16 PHILO_LOOPS = 1000;

#define PHILOSOPHERS 15

#define NTHREADS PHILOSOPHERS

#include "testaux.hxx"

static Cyg_Binary_Semaphore chopstick[PHILOSOPHERS];

static char pstate[PHILOSOPHERS+1];       // state of each philosopher

static cyg_ucount16 state_changes = 0;

// state_changes keep track of number of changes to pstate so

// we can exit after we've seen enough.

static Cyg_Mutex pstate_mutex;

static Cyg_Mutex cycle_mutex;

static inline int left(cyg_count8 i)

{

    return (0 == i) ? PHILOSOPHERS-1 : i-1 ;

}

static inline int right(cyg_count8 i)

{

    return (PHILOSOPHERS == i+1) ? 0 : i+1 ;

}

void change_state(int id, char newstate)

{

    if (PHILO_LOOPS == state_changes++)

        CYG_TEST_PASS_FINISH("Binary Semaphore 2 OK");

    pstate_mutex.lock(); {

        pstate[id] = newstate;

        bool all_hungry = true;         // until proved otherwise

        for(cyg_ucount8 i=0; i < PHILOSOPHERS; i++) {

            if('E' == pstate[i]) {

                CHECK('E' != pstate[left(i)]);

                CHECK('E' != pstate[right(i)]);

            }

            if('H' != pstate[i]) {

                all_hungry = false;

            }

        }

        // Theoretically it is possible for all the philosophers to be

        // hungry but not waiting on semaphores.  But in practice this

        // means something is wrong.

        CHECK(false == all_hungry);

    } pstate_mutex.unlock();

}

char get_state(int id)

{

    pstate_mutex.lock();

    char s = pstate[id];

    pstate_mutex.unlock();

    return s;

}

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

// Thread to behave like a philosopher

void Philosopher( CYG_ADDRESS id )

{

    Cyg_Thread *self = Cyg_Thread::self();

    Cyg_Binary_Semaphore *first_stick = &chopstick[id];

    Cyg_Binary_Semaphore *second_stick = &chopstick[(id+1)%PHILOSOPHERS];

    CHECK( id >= 0 && id < PHILOSOPHERS);

    // Deadlock avoidance. The easiest way to make the philosophers

    // behave is to make each pick up the lowest numbered stick

    // first. This is how it works out anyway for all the philosophers

    // except the last, who must have his sticks swapped.

    if( id == PHILOSOPHERS-1 )

    {

        Cyg_Binary_Semaphore *t = first_stick;

        first_stick = second_stick;

        second_stick = t;

    }

    // The following variable is shared by all philosophers.

    // It is incremented unprotected, but this does not matter

    // since it is only present to introduce a little variability

    // into the think and eat times.

    static int cycle = 0;

    for(;;)

    {

        // Think for a bit

        self->delay((id+cycle++)%12);    // Cogito ergo sum...

        // I am now hungry, try to get the chopsticks

        change_state(id,'H');

        // Get the sticks

        first_stick->wait();

        second_stick->wait();

        // Got them, now eat

        change_state(id,'E');

        // Check that the world is as I think it is...

        CYG_TEST_CHECK( !first_stick->posted(),

                        "Not got first stick");

        CYG_TEST_CHECK( !second_stick->posted(),

                        "Not got second stick");

        CYG_TEST_CHECK( get_state(left(id)) != 'E',

                        "Left neighbour also eating!!");

        CYG_TEST_CHECK( get_state(right(id)) != 'E',

                        "Right neighbour also eating!!");

        self->delay((id+cycle++)%6);    // munch munch

        // Finished eating, put down sticks.

        change_state(id,'T');

        // put sticks back on table

        first_stick->post();

        second_stick->post();

    }

}

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

void bin_sem2_main( void )

{

    CYG_TEST_INIT();

    if (cyg_test_is_simulator)

        PHILO_LOOPS = 100;

    for( int i = 0; i < PHILOSOPHERS; i++ )

    {

        pstate[i] = 'T';            // starting state

        new_thread(Philosopher, i);

        // make the matching chopstick present

        chopstick[i].post();

    }

    Cyg_Scheduler::scheduler.start();

}

externC void

cyg_start( void )

{

#ifdef CYGSEM_HAL_STOP_CONSTRUCTORS_ON_FLAG

    cyg_hal_invoke_constructors();

#endif

    bin_sem2_main();

}

// EOF bin_sem2.cxx