Re-entrant locking vs blocking

locks.cs

class A
{
    private object _lock = new object();

    public void foo()
    {
        lock(_lock)
        {
            do_something();
        }
    }

    public void bar()
    {
        lock(_lock)
        {
            while(condition)
                foo();
            do_something_else();
        }
    }
}


class B
{
    private object _lock = new object();

    private void foo_have_lock()
    {
        do_something();
    }

    public void foo()
    {
        lock(_lock)
        {
            foo_have_lock();
        }
    }

    public void bar()
    {
        lock(_lock)
        {
            while(condition)
                foo_have_lock();
            do_something_else();
        }
    }
}