GHC.IO.Exception.Deadlock is unused and could be removed
The Deadlock
exception
-- |There are no runnable threads, so the program is deadlocked.
-- The @Deadlock@ exception is raised in the main thread only.
data Deadlock = Deadlock
is currently never thrown by the RTS and could be removed.
I don't know what the process is for removing something from base
but I guess we first have to deprecate it and remove in a few releases.