Dinning Philosophers' Problem Using Conditional Variables

[knowLittle]

Homework Statement

I can't see where the problem is in the following pseudo-code.
I recall from class that the problem is based on the signal calls and wait call in pickup() and putdown()

Thank you.

Homework Equations

class Monitor R()
{
	bool forks[5]; // all true

	condition c[5];

	void pickup(i)
	{
		left =i;
		right=(i+1)%5;

		if (forks[left])
			forks[left]=F;

		if (forks[right])
			forks[right]=F;

		while( forks[left]==F || forks[right]==F )
			wait(c[i])

		forks[left]=F;
		forks[right]=F;
	}

	void putdown(i)
	{
		lphil=(i+4)%5;
		rphil=(i+1)%5;

		left=i;
		right=(i+1)%5;

		forks[left]=T;
		forks[right]=T;

		signal( c[lphil]);
		signal( c[rphil] );

	}
}

 

[LightHero]

The ProblemThe problem with this pseudo-code is that the signal calls in the putdown() method are in the wrong order. The left fork (forks

) should be signaled first, and then the right fork (forks

) should be signaled second. This ensures that the philosophers will pick up their forks in the correct order.​