Programming Forums - Regarding Dining Philosophers Problem

I have finally written the code to solve the Dining philosopher problem using a virtual distributed system with message passing (as a mean of communication between each created site). However, when i run the program, it hangs.

The following is the code in which sites are created and the dining philosopher problem is handled using semaphores. I can successfully create sites ( I have tested it) so i know the problem comes from the Philo() function.
#include <stdio.h>

#include <time.h>

#include "vds.h"

#include "comm.h"

#include "queue.c"

#include <stdlib.h>

#include <unistd.h>



#define MEALS 10

#define EATING 0

#define THINKING 1

#define HUNGRY 2

#define THINK_TIME 4

#define EAT_TIME 4

#define N_PHIL 5



int chopstick[5] = {1,1,1,1,1};

int mutex = 1;

Queue block_mutex;

Queue block_chopstick[5];



void test();

void Philo();

void think(int ph_id);

void eat(int ph_id,int meal);

void put_forks(int ph_id);

void get_forks(int ph_id);

int Request(int chopstick,int philosopher);

void Release (int chopstick,int philosopher);

void sem_wait(int chopstick_num, char* type);

void sem_signal(int chopstick_num, char* type);





int main(argc, argv)

int argc;

char *argv[];

{

        int  sid;





        /*

         * 

         * Site Initialization

         *

         *

         */

        setbuf( stdout, NULL ); /* no output buffering */



        if (argc != 4) {

                fprintf(stderr, "Usage: %s <SID> <NS HOST> <NS PORT>\n", argv[0]);

                exit(ERROR);

        }



        if (SiteSetup(atoi(argv[1]), argv[2], atoi(argv[3])) == ERROR) {

                fprintf(stderr, "SiteInit(%d) failed.\n", atoi(argv[1]));

                exit(ERROR);

        }



        printf("I am site %d. I am up and running\n", atoi(argv[1]));





        Philo();        /* This is a simple test routine. You should comment it out */



        /*

         *

         * Lab 2 Protocol

         *

         * Philo_Init()

         * while ( 1 ) {        

         *   Philosophers simulation code

         *

          * }

         *

         */







        /*

         * 

         * Site Termination

         *

         *

         */

        SiteExit();

}





void Philo()

{

     char *MSG = (char *)malloc(MAX_MSG_LEN);

     int i, sender;

     char delims[] = " ";   

     char *result = NULL;   

      

     block_mutex = CreateQueue(5);

     

     for(i=0;i<5;i++)

        block_chopstick[i] = CreateQueue(2);

     

     srand(MySID);

     if(MySID>=1 && MySID<=5)

     {

       while(1)

       {

              for (i=0;i<MEALS;i++)

              {

                think(MySID);

                get_forks(MySID);

                eat(MySID,i);

                put_forks(MySID);

              }

              printf("Philosopher %d's thread has exited\n",MySID);

        }    

     }

     else

     if(MySID == 6)  //if I am the site responsable for synchronization

     {

       //Do the work for the semaphores, increments and decrements 

       Receive(MSG, &sender);

       result = strtok( MSG, delims );

       if(strcmp(result,"Wait")==0)  //check if the message received corresponds to a sem_wait

       {

         result = strtok( NULL, delims ); 

         if(strcmp(result,"chopstick")==0) //check if the semaphore needed to be handled is "chopstick"

         {

             result = strtok( NULL, delims );

             for(i=0;i<5;i++)

             {

                 if(i == atoi(result))

                 {

                  chopstick[i]--;

                  if(chopstick[i]<0)

                    Enqueue(sender,block_chopstick[i]);//BLOCK the philosopher, put on waiting queue of this chopstick

                  else

                      Send("OK", sender);

                  }

             }

         }

         else

         if(strcmp(result,"mutex")==0) //check if the semaphore needed to be handled is "mutex"

         {

                  mutex--;

                  if(mutex<0)

                    Enqueue(sender,block_mutex);//BLOCK the philosopher, put on waiting queue -> mutex[sender]=0

                  else

                      Send("OK", sender); 

         }

       } //end of sew-wait handling

       else  

       if(strcmp(result,"Signal")==0)  //check if the message received corresponds to a sem_signal

       {

         result = strtok( NULL, delims ); 

         if(strcmp(result,"chopstick")==0) //check if the semaphore needed to be handled is "chopstick"

         {

             result = strtok( NULL, delims );

             for(i=0;i<5;i++)

             {

                 if(i == atoi(result))

                 {

                  chopstick[i]++;

                  if(chopstick[i]<=0)

                    Dequeue(block_chopstick[i]);//NBLOCK philosopher waiting on this chopstick from the blocking queue of this chopstick

                  Send("OK", sender);

                  }

             }

         }

         else

         if(strcmp(result,"mutex")==0) //check if the semaphore needed to be handled is "mutex"

         {

                  mutex++;

                  if(mutex<=0)

                    Dequeue(block_mutex);//NBLOCK philosopher waiting on mutex from the blocking queue of mutex

                  Send("OK", sender); 

         }

       }  //end of sem_signal handling           

    

     

    }//end of job for site responsable for synchronization 

    

} 

 

 

 

int Request(int chopstick,int philosopher)

{

        return 1;

}



void Release (int chopstick,int philosopher)

{

}

 

void sem_wait(int chopstick_num, char* type)

{

     char *MSG = (char *)malloc(MAX_MSG_LEN);

     char* string;

     int i,sender=6;

     if (strcmp(type,"chopstick")==0) //if dealing with semaphore "chopstick"

     {

          for(i=0;i<N_PHIL;i++)

          {

             if(i==chopstick_num)

             {

                sprintf(string, "Wait %s %d", type, i);

                Send(string, 6);

             }

          }

     }

     else

     if(strcmp(type,"mutex")==0)  //if dealing with semaphore mutex

     {

                sprintf(string, "Wait mutex");   

                Send(string, 6);

     }  

     Receive(MSG, &sender);

}





void sem_signal(int chopstick_num, char* type)

{

     char *MSG = (char *)malloc(MAX_MSG_LEN);

     char* string;

     int i,sender=6;

     if (strcmp(type,"chopstick")==0) //if dealing with semaphore "chopstick"

     {

          for(i=0;i<N_PHIL;i++)

          {

             if(i==chopstick_num)

             {

                sprintf(string, "Signal %s %d", type, i);

                Send(string, 6);

             }

          }

     }

     else

     if(strcmp(type,"mutex")==0)  //if dealing with semaphore mutex

     {

                sprintf(string, "Signal mutex");   

                Send(string, 6);

     }  

     Receive(MSG, &sender);

}





      

void think(int ph_id)

{

   int wait_time;

   wait_time=rand()%THINK_TIME+1;

   printf("\tPhilosopher %d is thinking for %d seconds.\n",ph_id,wait_time);

   sleep(wait_time);

}





void get_forks(int ph_id)

{

   int left=0,right=0;

   while(!left){

           sem_wait(-1,"mutex");

        left=Request(ph_id-1,ph_id);

        sem_signal(-1,"mutex");

        if (!left)

           sleep(1);

   }

   sem_wait(ph_id-1,"chopstick");

   while(!right){

        sem_wait(-1,"mutex");

        right=Request((ph_id)%N_PHIL,ph_id);

        sem_signal(-1,"mutex");

        if (!right)

        {

           sleep(1);

        }

   }

   sem_wait((ph_id)%N_PHIL,"chopstick");

}





void eat(int ph_id,int meal)

{

   int wait_time;

   wait_time=rand()%EAT_TIME+1;

   printf("\tPhilosopher %d is eating meal %d for %d seconds.\n",ph_id,meal+1,wait_time);

   sleep(wait_time);

}





void put_forks(int ph_id)

{

   int i;

   sem_wait(-1,"mutex");

   Release(ph_id-1,ph_id);

   Release((ph_id)%N_PHIL,ph_id);

   sem_signal(ph_id-1,"chopstick");

   sem_signal((ph_id)%N_PHIL,"chopstick");

   sem_signal(-1,"mutex");

}







void test()

{

        /*

         * To test: read, understand, then issue the command: 

          * vds <filename>, where <filename> is in local dir and 

         * contains:

         * 

         * ------ start file

         * 3

         * 1 sand

         * 2 sand

         * 3 sand

         * <your vds bin path>

         * ------ end file

         *

         */



    char *MSG = (char *)malloc(MAX_MSG_LEN);

        int sender;



        sleep(3);

        if (MySID==3)  {

                sleep(3); 

                Send("Hi, I am 3 sending you my greetings\n\0", 2);

        }

        else if (MySID==2) {

                Send("Hi, I am 2 sending you my greetings\n\0", 3);

        }



        if(MySID==3 || MySID==2) {

                Receive(MSG, &sender);

                printf("Site %d: Received this msg fm site %d: %s\n", MySID, sender, MSG);

        }

        

}
The output it produces is:
http://img186.imageshack.us/my.php?image=outputxm7.jpg

it doesnt seem to execute the getforks(),eat(), putforks() functions....

Anybody can help me out with it?