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

//

//        kphilo.c

//

//        A test of the dining philosophers problem

//

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

//####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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//####ECOSGPLCOPYRIGHTEND####

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

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

//

// Author(s):     dsm

// Contributors:    dsm

// Date:          1998-02-24

// Description:   A test of the dining philosophers problem

//####DESCRIPTIONEND####

// 

#include <cyg/kernel/kapi.h>

#include <cyg/infra/cyg_ass.h>

#include <cyg/kernel/diag.h>

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

// Data for the philosophers problem

#define PHILOSOPHERS    15               // number of philosophers

#define STACKSIZE       (2*1024)        // size of thread stack

// array of stacks for philosopher threads

char thread_stack[PHILOSOPHERS][STACKSIZE];

// array of threads.

cyg_thread thread[PHILOSOPHERS];

cyg_handle_t thread_handle[PHILOSOPHERS];

// array of chopsticks

cyg_sem_t chopstick[PHILOSOPHERS];

cyg_ucount32 data_index;

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

// State recording and display

static char pstate[PHILOSOPHERS+1];     // state vector showing what each

                                        // philosopher is doing

cyg_mutex_t state_mutex;

#ifdef CYG_HAL_MN10300_MN103002

static cyg_count8 eaters = 0;

#endif

void change_state(int id, char newstate)

{

    cyg_mutex_lock(&state_mutex);

#ifdef CYG_HAL_MN10300_MN103002

    if( pstate[id] == 'E' ) eaters--;

    if( newstate == 'E' ) eaters++;

//    led(eaters);

#endif

    pstate[id] = newstate;

    diag_write_string(pstate);

#if 0

    diag_write_char(' ');

    diag_write_dec(Cyg_Scheduler::get_thread_switches());

#endif    

    diag_write_char('\n');

    cyg_mutex_unlock(&state_mutex);

}

char get_state( int id)

{

    char s;

    cyg_mutex_lock(&state_mutex);

    s = pstate[id];

    cyg_mutex_unlock(&state_mutex);

    return s;

}

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

// Thread to behave like a philosopher

void Philosopher( cyg_addrword_t vid )

{

    cyg_uint32 id = (cyg_uint32)vid;

    cyg_sem_t *first_stick = &chopstick[id];

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

#ifdef CYGPKG_INFRA_DEBUG

    int left_philo = ((id==0)?PHILOSOPHERS:id)-1;

    int right_philo = (id==PHILOSOPHERS-1)?0:(id+1);

#endif

    CYG_ASSERT( id >= 0 && id < PHILOSOPHERS, "Bad id");

    // 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_sem_t *t = first_stick;

        first_stick = second_stick;

        second_stick = t;

    }

    for(;;)

    {

        cyg_ucount32 val;

        // 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 volatile int cycle = 0;

        // Think for a bit

        cyg_thread_delay((id+cycle++)%12);    // Cogito ergo sum...

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

        change_state(id,'H');

        // Get the first stick

        cyg_semaphore_wait(first_stick);

        // Get the second stick

        cyg_semaphore_wait(second_stick);

        // Got them, now eat

        change_state(id,'E');

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

        cyg_semaphore_peek( first_stick, &val);

        CYG_ASSERT( val == 0, "Not got first stick");

        cyg_semaphore_peek( second_stick, &val);

        CYG_ASSERT( val == 0, "Not got second stick");

        CYG_ASSERT( get_state(left_philo) != 'E', "Left neighbour also eating!!");

        CYG_ASSERT( get_state(right_philo) != 'E', "Right neighbour also eating!!");

        cyg_thread_delay((id+cycle++)%6);    // munch munch

        // Finished eating, put down sticks.

        change_state(id,'T');

        cyg_semaphore_post( first_stick );

        cyg_semaphore_post( second_stick );

    }

}

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

externC void

cyg_start( void )

{

    int i;

    diag_init();

    diag_write_string("Philosophers\n");

    diag_write_string("Started\n");

    // Zero last element in state so it acts like

    // a string.

    pstate[PHILOSOPHERS] = 0;

#if 1

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

    {

        change_state(i,'T');            // starting state

        cyg_thread_create(4, Philosopher, (cyg_addrword_t)i, "philosopher",

            (void *)(&thread_stack[i]), STACKSIZE,

            &thread_handle[i], &thread[i]);

        // resume it

        cyg_thread_resume(thread_handle[i]);

        // and make the matching chopstick present

        cyg_semaphore_init( &chopstick[i], 1);

    }

#endif

    // Get the world going

    cyg_scheduler_start();

}

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

// EOF kphilo.c