Different isolates can run concurrently on different threads, so pegging the CPU in one isolate doesn't block any others. Also, if a worker spends more than 50ms of CPU time on a request, we cancel it, terminating execution of the worker even if it's in an infinite loop. (Almost all non-buggy Workers we've seen in practice use more like 0ms-2ms per request. Note this is CPU time; time spent waiting for network replies doesn't count.)
