kphilo.c

eCos1.31版

//==========================================================================
//
//        kphilo.c
//
//        A test of the dining philosophers problem
//
//==========================================================================
//####COPYRIGHTBEGIN####
//                                                                          
// -------------------------------------------                              
// The contents of this file are subject to the Red Hat eCos Public License 
// Version 1.1 (the "License"); you may not use this file except in         
// compliance with the License.  You may obtain a copy of the License at    
// http://www.redhat.com/                                                   
//                                                                          
// Software distributed under the License is distributed on an "AS IS"      
// basis, WITHOUT WARRANTY OF ANY KIND, either express or implied.  See the 
// License for the specific language governing rights and limitations under 
// the License.                                                             
//                                                                          
// The Original Code is eCos - Embedded Configurable Operating System,      
// released September 30, 1998.                                             
//                                                                          
// The Initial Developer of the Original Code is Red Hat.                   
// Portions created by Red Hat are                                          
// Copyright (C) 1998, 1999, 2000 Red Hat, Inc.                             
// All Rights Reserved.                                                     
// -------------------------------------------                              
//                                                                          
//####COPYRIGHTEND####
//==========================================================================
//#####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