>> The problem is in Unix filesystems themselves. They are too racy to do anything guaranteed to work.
> What is the race with notification? Or what races are there that can't be fixed by a second notification and no guarantee that no spurious notifications are sent?
One answer to myself: http://lwn.net/Articles/361566/ points out that inotify doesn't let you exclude changes to files that you caused yourself, so that if you update a file every time it is modified you will get into a loop. Sounds like a somewhat specialised use case, but I'm sure that there is a good reason for it.