Let's make with the semaphores already! I think SOME hash table
lookeruppers (and rehashinators) should grab the table's (new)
semaphore before traipsing through its buckets...
That would make the hash table abstraction substantially more complex
and harder to understand, probably harm the performance that is the
sole reason to use hash tables instead of other data structures, and,
if you're not extremely careful with the engineering, make the whole
system very easily deadlock-prone.