Why is my producer-consumer blocking?
- by User007
My code is here: http://pastebin.com/Fi3h0E0P
Here is the output
0
Should we take order today (y or n): y
Enter order number: 100
More customers (y or n): n
Stop serving customers right now. Passing orders to cooker:
There are total of 1 order(s)
1
Roger, waiter. I am processing order #100
The goal is waiter must take orders and then give them to the cook. The waiter has to wait cook finishes all pizza, deliver the pizza, and then take new orders.
I asked how P-V work in my previous post here.
I don't think it has anything to do with \n consuming? I tried all kinds of combination of wait(), but none work.
Where did I make a mistake?
The main part is here:
//Producer process
if(pid > 0)
{
while(1)
{
printf("0");
P(emptyShelf); // waiter as P finds no items on shelf;
P(mutex); // has permission to use the shelf
waiter_as_producer();
V(mutex); // cooker now can use the shelf
V(orderOnShelf); // cooker now can pickup orders
wait();
printf("2");
P(pizzaOnShelf);
P(mutex);
waiter_as_consumer();
V(mutex);
V(emptyShelf);
printf("3 ");
}
}
if(pid == 0)
{
while(1)
{
printf("1");
P(orderOnShelf); // make sure there is an order on shelf
P(mutex); //permission to work
cooker_as_consumer(); // take order and put pizza on shelf
printf("return from cooker");
V(mutex); //release permission
printf("just released perm");
V(pizzaOnShelf); // pizza is now on shelf
printf("after");
wait();
printf("4");
}
}
So I imagine this is the execution path:
enter waiter_as_producer, then go to child process (cooker), then transfer the control back to parent, finish waiter_as_consumer, switch back to child. The two waits switch back to parent (like I said I tried all possible wait() combination...).
