On Sat, 2016-06-18 at 11:24 -0400, Jamal Hadi Salim wrote: > On 16-06-18 11:16 AM, Eric Dumazet wrote: > > >> Given an update/replace of an action is such a rare occassion, what > >> is wrong with init doing a spin lock on existing action? > >> Sure, there is performance impact on fast path at that point - but: > >> as established update/replace is _a rare occassion_ ;-> > > > > The potential 'problem' is not the write side, but the read side. > > > > If you read say 3 values <A, B, C> you might want to read them in a > > consistent way, instead of <new_A, old_B, old_C> > > > > That part i get. > What i meant is: while the fast path is doing rcu_read_lock() > of <A, B, C> and on the rare occassion that _init() is doing a > write to <A,B,C> then if it should spin lock it would not corrupt > what fast path sees as <A, B, C> during the transition. > Am i misunderstanding?
Yes, I do not see how a change in the write side can help. You probably need a bit of coffee ;)
