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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 Free Software Foundation, Inc.
//
// eCos is free software; you can redistribute it and/or modify it under
// the terms of the GNU General Public License as published by the Free
// Software Foundation; either version 2 or (at your option) any later
// version.
//
// eCos is distributed in the hope that it will be useful, but WITHOUT
// ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
// FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
// for more details.
//
// You should have received a copy of the GNU General Public License
// along with eCos; if not, write to the Free Software Foundation, Inc.,
// 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
//
// As a special exception, if other files instantiate templates or use
// macros or inline functions from this file, or you compile this file
// and link it with other works to produce a work based on this file,
// this file does not by itself cause the resulting work to be covered by
// the GNU General Public License. However the source code for this file
// must still be made available in accordance with section (3) of the GNU
// General Public License v2.
//
// This exception does not invalidate any other reasons why a work based
// on this file might be covered by the GNU General Public License.
// -------------------------------------------
// ####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
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