Question

I had designed a Stack wrapper class. My confusion is, should I be using lock while popping or pushing objects to the stack variable “ParameterStack“. Please let me know, whether this class is thread safe or not.

public static class StackManager
{
    private static Stack ParameterStack = new Stack();

    public static T Pop<T>()
    {
        T RawObject;
        T Result = default(T);

        lock (ParameterStack)
        {
            RawObject = (T)ParameterStack.Pop();
        }

        if (RawObject != null && RawObject is T)
            Result = (T)RawObject;

        return (T)Result;
    }

    public static void Push<T>(T Data)
    {
        lock (ParameterStack)
        {
            ParameterStack.Push(Data);
        }
    }
}

I had created this StackManager class for learning purpose.

Answer 1

It looks OK. There is a (rather theoretical) argument that locking on ParameterStack itself is not totally safe because you don’t own the code. Suppose somewhere inside the Stack does a lock(this) , you could deadlock.

public static class StackManager
{
    private static Stack parameterStack = new Stack();
    private static object stackLock = new object();

    // now use lock(stackLock) instead of lock(ParameterStack)

}