Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S967925Ab3HIQDS (ORCPT ); Fri, 9 Aug 2013 12:03:18 -0400 Received: from co9ehsobe004.messaging.microsoft.com ([207.46.163.27]:1447 "EHLO co9outboundpool.messaging.microsoft.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934068Ab3HIQDR convert rfc822-to-8bit (ORCPT ); Fri, 9 Aug 2013 12:03:17 -0400 X-Forefront-Antispam-Report: CIP:149.199.60.83;KIP:(null);UIP:(null);IPV:NLI;H:xsj-gw1;RD:unknown-60-83.xilinx.com;EFVD:NLI X-SpamScore: -6 X-BigFish: VPS-6(zzbb2dI98dI9371Ic89bh146fI148cI1432I1447Izz1f42h208ch1ee6h1de0h1fdah2073h1202h1e76h1d1ah1d2ah1fc6hzzz2fh95h668h839h93fhd24hf0ah119dh1288h12a5h12a9h12bdh137ah13b6h1441h14ddh1504h1537h153bh162dh1631h1758h18e1h1946h19b5h1b0ah1d0ch1d2eh1d3fh1dfeh1dffh1e1dh1fe8h906i1155h192ch) Date: Fri, 9 Aug 2013 09:03:02 -0700 From: =?utf-8?B?U8O2cmVu?= Brinkmann To: Srinivas KANDAGATLA CC: Daniel Lezcano , Russell King , Stephen Boyd , Michal Simek , , Stuart Menefy , John Stultz , Thomas Gleixner , Subject: Re: Enable arm_global_timer for Zynq brakes boot References: <068436c6-ff98-428f-8875-bb1c6f86466b@TX2EHSMHS008.ehs.local> <51F97CE3.9030306@linaro.org> <15e19315-ce88-4d3c-bad9-0a37d9e52f6b@CO1EHSMHS007.ehs.local> <51F99747.4060901@linaro.org> <51FA9AE8.1060004@linaro.org> <1c83c081-60c6-49e3-a85c-f64dd5be0e60@CH1EHSMHS030.ehs.local> <51FA9F54.3060704@linaro.org> <5204C54A.9020105@st.com> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Disposition: inline In-Reply-To: <5204C54A.9020105@st.com> User-Agent: Mutt/1.5.21 (2010-09-15) X-RCIS-Action: ALLOW Message-ID: Content-Transfer-Encoding: 8BIT X-OriginatorOrg: xilinx.com X-FOPE-CONNECTOR: Id%0$Dn%*$RO%0$TLS%0$FQDN%$TlsDn% Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 8433 Lines: 178 On Fri, Aug 09, 2013 at 11:32:42AM +0100, Srinivas KANDAGATLA wrote: > On 08/08/13 18:11, Sören Brinkmann wrote: > > Hi Daniel, > > > > On Thu, Aug 01, 2013 at 07:48:04PM +0200, Daniel Lezcano wrote: > >> 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 have an idea, but no real evidence to prove it: > > Some of the registers in the arm_global_timer are banked per CPU. I.e. > > some code must be executed on the CPU the timer is associated with > > (struct clock_event_device.cpumask) to have the intended effect > > As far as I can tell, there is no guarantee, that the set_mode() > > and program_next_event() calls execute on the correct CPU. > > If this was correct, shutting down the timer for the CPU entering > > idle might actually shut down the timer for the running CPU, if > > set_mode() executes on the CPU which is _not_ about to enter idle. > > Hi Sören, > Am able to reproduce similar issue on StiH415 SOC by enabling both > global_timer and twd and using cpuidle driver like zynq. > > When CPU0 goes to idle, I noticed that the global timer used for > boardcast is actually scheduled on wrong cpu. > My traces for printk like this > printk("DEBUG: %s on CPU:%d CPUMASK:%s\n", __FUNCTION__, > smp_processor_id(), scpumask); > > shows: > > DEBUG: gt_clockevent_set_mode on CPU:1 CPUMASK: 0 > DEBUG: gt_clockevent_set_next_event on CPU:1 CPUMASK:0 > > Which indicates that setting the mode and next_event for a clkevent with > cpumask 0 is scheduled on cpu1, this will generate an global timer > interrupt on cpu1 rather than cpu0. > > This might be the reason for cpu0 not coming out of the cpu_idle_loop. Thanks for reproducing. I think so too. I had similar debug prints in set_mode and program_next event, which compared the passed struct clocke_event_device pointer with the this_cpu_ptr(gt_evt) pointer, which clearly indicate this mismatch. Sören -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/