Mutual exclusions, How to implement try_lock() method using Lamport's Bakery Algorithm?

Question

I'm trying to create a BakeryLock abstraction using Lamport's bakery algorithm and Lockable concept from C++. It's quite easy to implement lock(), unlock() methods. Could someone help me with an implementation of the try_lock() method? From documentation:

m.try_lock()

Effects: Attempts to acquire a lock for the current execution agent without blocking. If an exception is thrown, then a lock shall not have been acquired for the current execution agent.

Return type: bool

Returns: true if the lock was acquired, false otherwise.

Answer 1

I have come up with the following solution in C++, but haven't tested it fully yet.

bool ImprovedBakeryLock::try_lock(int i)
{
    Entering[i] = true;
    Number[i] = 1 + max(Number[1], ..., Number[NUM_THREADS]);
    Entering[i] = false;
    bool acquired = true;
    for (int j = 1; j <= NUM_THREADS && acquired; ++j) {
        if (Number[j] != 0 && Number[j] < Number[i]){
            acquired = false;
            Number[i] = 0;
        }
    }
    return acquired;
}