So that's a fine question to ask, and you've received many fascinating answers, but can I just suggest that this case - that is, applying patches that relate to

So that's a fine question to ask, and you've received many fascinating answers, but can I just suggest that this case - that is, applying patches that relate to the security of your processor cache - is a very fine reason for requiring a reboot, since it will ensure that your processor cache starts out fresh and all behaviors that cause data to be placed there are correctly following the patched behavior.