Dining Philosophers Example

 monitor dp

 {

 enum {thinking, hungry, eating} state[5];

 condition self[5];

 void pickup(int i)   // following slides

 void putdown(int i)   // following slides

 void test(int i)   // following slides

 void init()

 {

 for (int i = 0; i < 5; i++)

 state[i] = thinking;

 }

 }

 void pickup(int i)

 {

 state[i] = hungry;

 test[i];

 if (state[i] != eating)

 self[i].wait();

 }

 void putdown(int i) {

 state[i] = thinking;

 // test left and right neighbors

 test((i+4) % 5);

 test((i+1) % 5);

 }

 void test(int i) {

 if ( (state[(I + 4) % 5] != eating) &&

 (state[i] == hungry) &&

 (state[(i + 1) % 5] != eating)) {

 state[i] = eating;

 self[i].signal();

 }

 }