The descriptor returned by file-notify-add-watch is of the form (ID . DIR)
(at least when using inotify) and these descriptors are stored in a
hash-table using equal as comparator.

If multiple clients watch the same file and one of them removes its watch
via file-notify-rm-watch, the result is unpredictable. I.e. the function
removes some watch (I believe it is the last one added), but not necessarily
the one associated with the client calling file-notify-rm-watch on the
descriptor it got from calling file-notify-add-watch.

I've attached a test case for this.

Am I missing something here ?

-ap