The typical spin lock holds only one bit of data, but requires a full word of storage, because only full words can be read, modified, and written atomically in hardware. Consider, however, the hash table of the previous exercise. If we choose to employ a separate lock for each bucket of the table, explain how to implement a “two-level” locking scheme that couples a conventional spin lock for the table as a whole with a single bit of locking information for each bucket. Explain why such a scheme might be desirable, particularly in a table with external chaining.