Comment 134 for bug 124406

>Have you mapped the Ctrl key to the Caps Lock key?

Good catch.

Yes, I'm using swapcaps in xorg.

I used dumpkeys, swapped keycode 29 and 58, and ran the result through loadkeys.

When I ran emacs in a console, I did not get duplicated keypresses but I did get the missing key up event (based on the od -x output from the event1 device) -- the same thing I see when emacs is running in X. It looks like the "non-duplication" is because xorg is responsible for generating repeats in X and the kernel is responsible for generating repeats in the terminal. So the events from event1 are still wrong and the key is never being "released" -- it just isn't user-visible in the form of a repeating keypress. From a user standpoint, of course, this may not matter, since the key doesn't appear to be down to the user.

Interestingly enough, as you've noticed, I could not reproduce the problem when using the standard Control/Caps Lock mappings in the console -- only when the two are swapped. This may be because I simply can't release the lower-left control key quickly enough, but I did spend a while trying to get it to happen without luck.

Unless someone can produce this with the standard Control/Caps Lock mappings, I think that, as a user-visible bug, this can be narrowed to people who are using swapped caps in xorg.