Dining Philosophers Problem
The set up is a round table where there is rice on the centre of the table. There are philosophers seating at the table in a circle. There are objects called
- Chopsticks : Resources
- Philosopher : Processes
The philosophers have two states Eating, Think state.
- Eating State : Need Two chop sticks to eat
- Think State : Thinking state if resources are not available.
If you think about it if one philosopher is in a eating state then the neighbouring two will have a missing chop sticks to eat thus entering a forceful thinking state. But the one that is two chairs away can also enter the eating state. The philosopher can only pick one chopstick at a time.
When a philosopher picks a chopstick a wait() signal is sent to immediate neighbours and when they release it Signal() is sent.
do{
wait(chopstick[i]);
wait(chopstick[i+1]%5);
// eat
signal(chopstick[i]);
signal(chopstick[i+1]%5);
// thinking
}while(True);Deadlock Handling
- Allow at most 4 philosophers to be sitting simultaneously at the table.
- Allow a philosopher to pick up the forks only if both are available. That is in a Critical Section
- Use an asymmetric solution.
- An odd numbered philosopher picks up first the left chopstick and then the right chopstick or even.
Monitors
High level abstraction that provides a convenient and effective mechanism for process synchronization.
In the diagram the the initialization code can have values like wrt=1 or 0 depending on the needs or mutex = 1 or 0 from the value.
monitor DiningPhillosphers
{
enum{ THINKING; HUNGRY; EATING}
}References
Information
- date: 2025.02.22
- time: 12:22