Homework & Coursework Questions

#include "sema.h"
#define MAX_CHILD     40          /* max. # of child processes */
#define LIFETIME      30 /* max. lifetime of a process */
#define MAX_NTIME     20  /* max. time for normal work */
#define MAX_CTIME     10 /* max. time for critical work */
#define N             10
#define SHMKEY (key_t)0X10
#define SHMKEY1(key_t)0x11
int *espaco_aereo=0;
int *espaco_gate=0;
int gares=10;
main ()
{
 
 
        semaphore avioes, gate, fila, pista_mutex, ar_mutex;
        
 avioes = init_sem(15);
 gate = init_sem(10);
 fila = init_sem(4);
 pista_mutex= init_sem(1);
 ar_mutex= init_sem(1);
 
        int child_pid [MAX_CHILD], /* process ID's   */
  wait_pid;
        int i, j,   /* loop variables  */
  child_status;  /* return status of child */
 
 int shmid;
 char*addr;
 shmid=shmget(SHMKEY,10,0777|IPC_CREAT);
        addr=(char*)shmat(shmid,0,0);
        espaco_aereo=(int*)addr; 
 int shmid1;
 char*addr1;
 shmid1=shmget(SHMKEY,128,0777|IPC_CREAT);
        addr1=(char*)shmat(shmid1,0,0);
        espaco_gate=(int*)addr1; 
 
   for (i = 0; i < MAX_CHILD; ++i)
  {
    child_pid [i] = fork ();
    sleep(2);
    switch (child_pid [i])
    {
      case -1:    /* error: no process created */
 perror ("fork failed");        /*perro e igual ao printf*/
 exit (1);
 break;
      
 case 0:    /* child process  */
 
        //============== Aviões ====================
  
  P(ar_mutex); 
  if(*espaco_aereo <= 15){   
  *espaco_aereo=*espaco_aereo+1; 
  
  
  printf("O aereo TAP%d entrou no espaco aereo.\n", getpid());
  sleep(1);// ((unsigned int) rand () % MAX_NTIME);
            
          printf("existem %d avioes no ar.\n", *espaco_aereo);
  V(ar_mutex);
  P(gate);
  P(pista_mutex);
  //================ Gate ====================
  
  printf("o aereo TAP%d aterrou e entrou na gate \n", getpid());
  sleep(1);// ((unsigned int) rand () % MAX_NTIME);

  V(pista_mutex);
  P(ar_mutex);  
  *espaco_aereo=*espaco_aereo-1;
  V(ar_mutex);
  
  printf("o aereo TAP%d esta a desembarcar passageiros \n", getpid());
  
  sleep(2);
  printf("o aereo TAP%d está a embarcar passageiros \n", getpid());
  sleep(3);
  
  P(fila);
  V(gate);
  //================== fila =======================
   
   printf("o aereo TAP%d entrou na posicao da fila de espera\n", getpid());
   sleep(2);//((unsigned int) rand () % MAX_NTIME);
     
     
   V(fila);
   P(pista_mutex);
   
  //==================== Pista =========================
  printf("o aereo TAP%d descolou\n", getpid());
  
  sleep(1);// ((unsigned int) rand () % MAX_CTIME);
  V(pista_mutex);
  
  }
  
  else
      printf("o aereo %d foi desviado.\n", getpid());
      sleep(1);
      
 
 exit(0);
 break;
 
       default:    /* parent process  */
 if (i == (MAX_CHILD - 1)) /* all childs created ?  */
 {    /* yes -> wait for termination */
   for (j = 0; j < MAX_CHILD; ++j)
   {
     wait_pid = wait (&child_status); /*vai guardar o identificador do processo que terminou e desbloqueou o wait*/
     /*printf("O aviao com o numero de serie: %d aterrou e tem a matricula: %d", wait_pid, child_status);*/
     if (wait_pid == -1)
     {
       perror ("wait failed");
     };
   };
   printf ("All child processes have terminated.\n");
   
   rel_sem (avioes);
   rel_sem (gate);
   rel_sem (fila);
   rel_sem (pista_mutex);
   rel_sem (ar_mutex);
   shmdt(addr);
   shmctl(shmid,IPC_RMID,NULL);
   shmdt(addr1);
   shmctl(shmid1,IPC_RMID,NULL);
 };
    };     /* end switch   */
 };     /* end for*/
}