On Thu, Apr 21, 2016 at 07:07:51PM +0200, Rafael J. Wysocki wrote: > On Thu, Apr 21, 2016 at 2:33 PM, Peter Zijlstra <[email protected]> wrote: > > On Thu, Apr 21, 2016 at 09:09:43AM +0800, Wanpeng Li wrote: > >> >> Sometimes .update_curr hook is called w/o tasks actually running, it is > >> >> captured by: > >> >> > >> >> u64 delta_exec = rq_clock_task(rq) - curr->se.exec_start; > >> >> > >> >> We should not trigger cpufreq update in this case for rt/deadline > >> >> classes, and this patch fix it. > > > >> I add a print to print when delta_exec is zero for rt class, something > > > > So its zero, so what? > > > >> like below: > > > >> watchdog/5-48 [005] d... 568.449105: update_curr_rt: rt > >> delta_exec is zero > >> watchdog/5-48 [005] d... 568.449111: <stack trace> > >> => put_prev_task_rt > >> => pick_next_task_idle > > > > So we'll go idle, but as of this point we're still running the rt task. > > Skipping the update in that case might be the right thing to do, though.
It is; the patch looks fine, but the Changelog is entirely misleading/wrong. Its not because the task isn't running; it is. Its because we end up calling update_curr() multiple times and bailing when nothing changed is indeed the right thing.
