On Fri, Jan 20, 2023 at 08:27:03AM -0500, Joel Fernandes wrote: > > Sure, I know what the code currently does, I am asking why and it feels wrong. > > I suggest you slightly change your approach to not assuming the code should be bonafide correct and then fixing it (which is ok once in a while), and asking higher level questions to why things are the way they are in the first place (that is just my suggestion and I am not in a place to provide advice, far from it, but I am just telling you my approach — I care more about the code than increasing my patch count :P). > > If you are in an intermediate state, part way to a !nocb state — you may have > missed a nocb-related accel and wake, correct? Why does that matter? Once we > transition to a !nocb state, we do not do a post-qs-report accel+wake anyway > as we clearly know from the discussion. I'm confused. We are doing that acceleration on qs report for !nocb CPU, right? > So why do we need to do it if we > missed it for the intermediate stage? So, I am not fully sure yet what that > needac is doing and why it is needed. To summarize: * If the CPU is NOCB, all the callbacks advance and acceleration is performed by the rcuo/rcuog kthreads. * If the CPU is not NOCB, all the callbacks acceleration is performed by the CPU, such as in the case of rcu_report_qs_rdp(). * If the CPU is transitionning from NOCB to !NOCB or from !NOCB to NOCB, the kthreads may not be available to do the advance/acceleration, so we must do it locally. That's the needacc path. What am I missing? Thanks.
