On 08/01/2013 07:43 PM, Sören Brinkmann wrote: > On Thu, Aug 01, 2013 at 07:29:12PM +0200, Daniel Lezcano wrote: >> On 08/01/2013 01:38 AM, Sören Brinkmann wrote: >>> On Thu, Aug 01, 2013 at 01:01:27AM +0200, Daniel Lezcano wrote: >>>> On 08/01/2013 12:18 AM, Sören Brinkmann wrote: >>>>> On Wed, Jul 31, 2013 at 11:08:51PM +0200, Daniel Lezcano wrote: >>>>>> On 07/31/2013 10:58 PM, Sören Brinkmann wrote: >>>>>>> On Wed, Jul 31, 2013 at 10:49:06PM +0200, Daniel Lezcano wrote: >>>>>>>> On 07/31/2013 12:34 AM, Sören Brinkmann wrote: >>>>>>>>> On Tue, Jul 30, 2013 at 10:47:15AM +0200, Daniel Lezcano wrote: >>>>>>>>>> On 07/30/2013 02:03 AM, Sören Brinkmann wrote: >>>>>>>>>>> Hi Daniel, >>>>>>>>>>> >>>>>>>>>>> On Mon, Jul 29, 2013 at 02:51:49PM +0200, Daniel Lezcano wrote: >>>>>>>>>>> (snip) >>>>>>>>>>>> >>>>>>>>>>>> the CPUIDLE_FLAG_TIMER_STOP flag tells the cpuidle framework the >>>>>>>>>>>> local >>>>>>>>>>>> timer will be stopped when entering to the idle state. In this >>>>>>>>>>>> case, the >>>>>>>>>>>> cpuidle framework will call clockevents_notify(ENTER) and switches >>>>>>>>>>>> to a >>>>>>>>>>>> broadcast timer and will call clockevents_notify(EXIT) when >>>>>>>>>>>> exiting the >>>>>>>>>>>> idle state, switching the local timer back in use. >>>>>>>>>>> >>>>>>>>>>> I've been thinking about this, trying to understand how this makes >>>>>>>>>>> my >>>>>>>>>>> boot attempts on Zynq hang. IIUC, the wrongly provided TIMER_STOP >>>>>>>>>>> flag >>>>>>>>>>> would make the timer core switch to a broadcast device even though >>>>>>>>>>> it >>>>>>>>>>> wouldn't be necessary. But shouldn't it still work? It sounds like >>>>>>>>>>> we do >>>>>>>>>>> something useless, but nothing wrong in a sense that it should >>>>>>>>>>> result in >>>>>>>>>>> breakage. I guess I'm missing something obvious. This timer system >>>>>>>>>>> will >>>>>>>>>>> always remain a mystery to me. >>>>>>>>>>> >>>>>>>>>>> Actually this more or less leads to the question: What is this >>>>>>>>>>> 'broadcast timer'. I guess that is some clockevent device which is >>>>>>>>>>> common to all cores? (that would be the cadence_ttc for Zynq). Is >>>>>>>>>>> the >>>>>>>>>>> hang pointing to some issue with that driver? >>>>>>>>>> >>>>>>>>>> If you look at the /proc/timer_list, which timer is used for >>>>>>>>>> broadcasting ? >>>>>>>>> >>>>>>>>> So, the correct run results (full output attached). >>>>>>>>> >>>>>>>>> The vanilla kernel uses the twd timers as local timers and the TTC as >>>>>>>>> broadcast device: >>>>>>>>> Tick Device: mode: 1 >>>>>>>>> >>>>>>>>> Broadcast device >>>>>>>>> Clock Event Device: ttc_clockevent >>>>>>>>> >>>>>>>>> When I remove the offending CPUIDLE flag and add the DT fragment to >>>>>>>>> enable the global timer, the twd timers are still used as local timers >>>>>>>>> and the broadcast device is the global timer: >>>>>>>>> Tick Device: mode: 1 >>>>>>>>> >>>>>>>>> Broadcast device >>>>>>>>> >>>>>>>>> Clock Event Device: arm_global_timer >>>>>>>>> >>>>>>>>> Again, since boot hangs in the actually broken case, I don't see way >>>>>>>>> to >>>>>>>>> obtain this information for that case. >>>>>>>> >>>>>>>> Can't you use the maxcpus=1 option to ensure the system to boot up ? >>>>>>> >>>>>>> Right, that works. I forgot about that option after you mentioned, that >>>>>>> it is most likely not that useful. >>>>>>> >>>>>>> Anyway, this are those sysfs files with an unmodified cpuidle driver and >>>>>>> the gt enabled and having maxcpus=1 set. >>>>>>> >>>>>>> /proc/timer_list: >>>>>>> Tick Device: mode: 1 >>>>>>> Broadcast device >>>>>>> Clock Event Device: arm_global_timer >>>>>>> max_delta_ns: 12884902005 >>>>>>> min_delta_ns: 1000 >>>>>>> mult: 715827876 >>>>>>> shift: 31 >>>>>>> mode: 3 >>>>>> >>>>>> Here the mode is 3 (CLOCK_EVT_MODE_ONESHOT) >>>>>> >>>>>> The previous timer_list output you gave me when removing the offending >>>>>> cpuidle flag, it was 1 (CLOCK_EVT_MODE_SHUTDOWN). >>>>>> >>>>>> Is it possible you try to get this output again right after onlining the >>>>>> cpu1 in order to check if the broadcast device switches to SHUTDOWN ? >>>>> >>>>> How do I do that? I tried to online CPU1 after booting with maxcpus=1 >>>>> and that didn't end well: >>>>> # echo 1 > online && cat /proc/timer_list >>>> >>>> Hmm, I was hoping to have a small delay before the kernel hangs but >>>> apparently this is not the case... :( >>>> >>>> I suspect the global timer is shutdown at one moment but I don't >>>> understand why and when. >>>> >>>> Can you add a stack trace in the "clockevents_shutdown" function with >>>> the clockevent device name ? Perhaps, we may see at boot time an >>>> interesting trace when it hangs. >>> >>> I did this change: >>> diff --git a/kernel/time/clockevents.c b/kernel/time/clockevents.c >>> index 38959c8..3ab11c1 100644 >>> --- a/kernel/time/clockevents.c >>> +++ b/kernel/time/clockevents.c >>> @@ -92,6 +92,8 @@ void clockevents_set_mode(struct clock_event_device >>> *dev, >>> */ >>> void clockevents_shutdown(struct clock_event_device *dev) >>> { >>> + pr_info("ce->name:%s\n", dev->name); >>> + dump_stack(); >>> clockevents_set_mode(dev, CLOCK_EVT_MODE_SHUTDOWN); >>> dev->next_event.tv64 = KTIME_MAX; >>> } >>> >>> It is hit a few times during boot, so I attach a full boot log. I really >>> don't know what to look for, but I hope you can spot something in it. I >>> really appreciate you taking the time. >> >> Thanks for the traces. > > Sure. > >> >> If you try without the ttc_clockevent configured in the kernel (but with >> twd and gt), does it boot ? > > Absence of the TTC doesn't seem to make any difference. It hangs at the > same location.
Ok, IMO there is a problem with the broadcast device registration (may be vs twd). I will check later (kid duty) :) Thanks -- Daniel -- <http://www.linaro.org/> Linaro.org │ Open source software for ARM SoCs Follow Linaro: <http://www.facebook.com/pages/Linaro> Facebook | <http://twitter.com/#!/linaroorg> Twitter | <http://www.linaro.org/linaro-blog/> Blog -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/