On Wed, Oct 17, 2018 at 08:44:01AM -0700, Daniel Colascione wrote: > > Even if no one changes these specific flags we still need a lock due > > to rmw cycles on the field. For example fadvise can set or clear > > FMODE_RANDOM. It seems to use file->f_lock for synchronization. > > Compare-and-exchange will suffice, right? Only if all users use the compare and exchange, and right now they don't.