On Thu 17-10-19 11:25:47, David Laight wrote: > From: Michal Hocko > > Sent: 17 October 2019 12:05 > ... > > > Plus, I don't see any locking here, should this be WRITE_ONCE() at > > > minimum? > > > > Why would that matter? Do you expect several root processes race to set > > the value? > > One of them wins. No one is going to notice is the value is set an extra time.
Right, this is quite obvious. The question is whether/how much it really matters. > WRITE_ONCE() is rarely required. > Probably only if other code is going to update the value after seeing the > first write. > (eg if you are unlocking a mutex - although they have to be more complex) > > READ_ONCE() is a different matter. > IMHO the compiler shouldn't be allowed to do more reads than the source > requests. Right, we are talking about setting an int value. While nobody can rule out that the compiler splitting the single write into multiple ones I would be quite curious about seeing that... -- Michal Hocko SUSE Labs
