Deadlock happened due to mixed lock order.
CREATE/DROP function: wrlock(THR_LOCK_udf) -> lock(LOCK_open)
SELECT from view: lock(LOCK_open) -> rdlock(THR_LOCK_udf)

Fixed CREATE/DROP function so that LOCK_open does not intersect with
wrlock(THR_LOCK_udf).

10.0 is not affected: it doesn't hold LOCK_open while opening view.