On 05/27/14 12:39, Arnd Bergmann wrote: > On Tuesday 27 May 2014 12:33:38 Stephen Boyd wrote: >> On 05/27/14 12:27, Arnd Bergmann wrote: >>> On Tuesday 27 May 2014 11:53:59 Stephen Boyd wrote: >>>> On 05/27/14 11:49, Arnd Bergmann wrote: >>>>> You also commented in that thread about stop_critical_timings()/ >>>>> start_critical_timings(). Corey, can you look at that, too? I >>>>> think it's designed to avoid the issue you are seeing but >>>>> for some reason doesn't. >>>> I sent a patch last week to "solve" this problem. I'm not sure if it's >>>> right but it works for me. >>>> >>>> https://lkml.org/lkml/2014/5/19/607 >>> I think that one was also wrong, as the intention of the existing >>> stop_critical_timings() function is already to do the same that >>> Corey's patch does, i.e. stop the trace before we go to idle as >>> if we were turning IRQs on. >> stop_critical_timings() is called in the generic idle loop. It looks >> like stop_critical_timings() just isn't written correctly. All it does >> is turn off the tracer, but it doesn't prevent future calls to >> spinlocks, etc. from causing the tracer to turn on again between calls >> to stop/start_critical_timings(). It seems better to prevent any more >> tracing from happening between a call to stop_critical_timings() and >> start_critical_timings() so we don't have to litter calls to that >> function throughout the idle path. > But are there any such calls in the idle function? I understand what > you are doing in your patch, but I don't see why you have to actually > do it. > Yes in my build it happens immediately after in rcu_enter_idle(). It would also happen if you had a cpuidle driver that notified the core that the timers stop during idle (FEAT_C3_STOP). In that case we would call clockevents_notify() which will call raw_spin_lock_irqsave(). -- Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted by The Linux Foundation -- To unsubscribe from this list: send the line "unsubscribe linux-rt-users" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
