Concurrent Affairs: Reader/Writer Locks and the ResourceLock Library

摘要

If multiple threads concurrently execute code that writes to or modifies a resource, then obviously the resource must be protected with a thread synchronization lock to ensure that the resource doesn't get corrupted. However, it is common to have a resource that is occasionally written to but frequently read from. If multiple threads are concurrently reading a resource, using a mutual exclusive lock hurts performance significantly because only one thread at a time is allowed to read from the resource. It's far more efficient to allow all the threads to read the resource simultaneously, and it's fine to do this if all of the threads treat the resource as read-only and do not attempt to write to or modify it.