On Wed, Jul 26, 2017 at 11:59:12AM +0530, Viresh Kumar wrote: > 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.
Argh, what a horrible mess.. :-(
