On 24-07-17, 15:47, Peter Zijlstra wrote: > I said nothing about the shared locking. That is indeed required. All I > said is that those two tests you add could be left out.
I was right, I didn't understood your comment at all :( > > > That would then continue to process the iowait and other accounting > > > stuff, but stall the moment we call into the actual driver, which will > > > then drop the request on the floor as per the first few hunks. > > > > I am not sure I understood your comment completely though. > > Since we call cpufreq_update_util(@rq, ...) with @rq->lock held, all > such calls are in fact serialized for that cpu. Yes, they are serialized but .. > Therefore the cpu != > current_cpu test you add are pointless. .. I didn't understand why you said so. This check isn't there to take care of serialization but remote callbacks. > Only once we get to the actual cpufreq driver (intel_pstate and others) > do we run into the fact that we might not be able to service the request > remotely. We never check for remote callbacks in drivers. > But since you also add a test there, that is sufficient. No. The diff for intel-pstate that you saw in this patch was for the case where intel-pstate works directly with the scheduler (i.e. no schedutil governor). The routine that gets called with schedutil is intel_cpufreq_target(), which doesn't check for remoteness at all. -- viresh