On Tue, May 22, 2018 at 11:09:08AM +0200, Roman Penyaev wrote: > On Mon, May 21, 2018 at 5:33 PM, Paul E. McKenney > <paulmck@xxxxxxxxxxxxxxxxxx> wrote: > > On Mon, May 21, 2018 at 08:16:59AM -0700, Linus Torvalds wrote: > >> On Mon, May 21, 2018 at 6:51 AM Roman Penyaev < > >> roman.penyaev@xxxxxxxxxxxxxxxx> wrote: > >> > >> > No, I continue from the pointer, which I assigned on the previous IO > >> > in order to send IO fairly and keep load balanced. > >> > >> Right. And that's exactly what has both me and Paul nervous. You're no > >> longer in the RCU domain. You're using a pointer where the lifetime has > >> nothing to do with RCU any more. > >> > >> Can it be done? Sure. But you need *other* locking for it (that you haven't > >> explained), and it's fragile as hell. > > > > He looks to actually have it right, but I would want to see a big comment > > on the read side noting the leak of the pointer and documenting why it > > is OK. > > Hi Paul and Linus, > > Should I resend current patch with more clear comments about how careful > caller should be with a leaking pointer? Also I will update read side > with a fat comment about "rcu_assign_pointer()" which leaks the pointer > out of RCU domain and what is done to prevent nasty consequences. > Does that sound acceptable? That sounds good to me. Thanx, Paul
