Solución ejercicio 7

Hilo h1

for (int i = 0; i<2; i++){ //#1
      down(s) ;            //#2
      f();                 //#3
      up(s);               //#4

}

Hilo h2

for (int i = 0; i<2; i++){ //#1
      down(s) ;            //#2
      f();                 //#3
      up(s);               //#4

}

     X = El proceso pasa a estado bloqueado.
     / = El proceso pasa a estado preparado.
     > = Fin de su ejecucion


     | #1| #2| #3|   |   | #4| #1| #2|   |   |   | #3| #4| #1|   |   |   |   |   |   |
   h1|---|---|---|   |   |---|---|---X   |   /   |---|---|--->   |   |   |   |   |   |
     |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |
     |   |   |   | #1| #2|   |   |   | #3| #4| #1|   |   |   | #2| #3| #4| #1|   |   |
   h2|   |   |   |---|---X   /   |   |---|---|---|   |   |   |---|---|------->   |   |
     |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |
     |___|___|___|___|___|___|___|___|___|___|___|___|___|___|___|___|___|___|___|___|
     0   1   2   3   4   5   6   7   8   9   10  11  12  13  14  15  16  17  18  19  20