Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755427Ab3HFJSZ (ORCPT ); Tue, 6 Aug 2013 05:18:25 -0400 Received: from co9ehsobe001.messaging.microsoft.com ([207.46.163.24]:38968 "EHLO co9outboundpool.messaging.microsoft.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755217Ab3HFJSX convert rfc822-to-8bit (ORCPT ); Tue, 6 Aug 2013 05:18:23 -0400 X-Forefront-Antispam-Report: CIP:62.221.5.235;KIP:(null);UIP:(null);IPV:NLI;H:xir-gw1;RD:unknown-62-221-5-235.ipspace.xilinx.com;EFVD:NLI X-SpamScore: -1 X-BigFish: VPS-1(zzbb2dI98dI9371Ic89bh146fI1432I4015I1447Izz1f42h208ch1ee6h1de0h1fdah2073h1202h1e76h1d1ah1d2ah1fc6hzzz2fh95h668h839h93fhd24hf0ah119dh1288h12a5h12a9h12bdh137ah13b6h1441h1504h1537h153bh162dh1631h1758h18e1h190ch1946h19b4h19b5h19c3h1b0ah1be0h1d0ch1d2eh1d3fh1dfeh1dffh19b6n1155h192ch) Date: Tue, 6 Aug 2013 11:18:10 +0200 From: Michal Simek User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130330 Thunderbird/17.0.5 MIME-Version: 1.0 To: Daniel Lezcano CC: =?UTF-8?B?U8O2cmVuIEJyaW5rbWFubg==?= , Stuart Menefy , Stephen Boyd , John Stultz , Thomas Gleixner , Russell King , Michal Simek , , Subject: Re: Enable arm_global_timer for Zynq brakes boot References: <51F77D93.4030505@linaro.org> <51F97842.6050200@linaro.org> <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> <712d31e9-3584-48e1-aa9f-55bc94fa62c9@DB9EHSMHS001.ehs.local> <5200B7FE.4000306@linaro.org> In-Reply-To: <5200B7FE.4000306@linaro.org> X-Enigmail-Version: 1.5.2 Content-Type: text/plain; charset="UTF-8" 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: 8423 Lines: 177 On 08/06/2013 10:46 AM, Daniel Lezcano wrote: > On 08/06/2013 03:28 AM, 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 will check later (kid duty) :) >> >> I was actually waiting for an update from your side and did something >> else, but I seem to have run into this again. I was overhauling the >> cadence_ttc (patch attached, based on tip/timers/core). And it seems to >> show the same behavior as enabling the global_timer. With cpuidle off, it >> works. With cpuidle, on it hangs. Removing the TIMER_STOP flag from the >> C2 state makes it boot again. >> It works just fine on our 3.10 kernel. > > This is not necessary related to the bug. If the patch you sent broke > the cadence_ttc driver, when you use it (with the TIMER_STOP), you will > be stuck. Removing the flag, may signifies you don't use the broadcast > timer, hence the bug is not surfacing. > > Going back to the bug with the arm_global_timer, what is observed is the > broadcast timer is *shutdown* when the second cpu is online. > > I have to dig into the kernel/time/clockevents.c|tick-*.c because IMO > the issue is coming from there but before I have to reproduce the bug, > so find a board I have where I can add the arm_global_timer. > >> Another thing I noticed - probably unrelated but hard to tell: On >> 3.11-rc1 and later my system stops for quite some time at the hand off >> to userspace. I.e. I see the 'freeing unused kernel memory...' line and >> sometimes the following 'Welcome to Buildroot...' and then it stops and >> on good kernels it continues after a while and boots through and on bad >> ones it just hangs there. > > did you try to dump the stacks with magic-sysrq ? Or git bisect ? Soren: Are you able to replicate this issue on QEMU? If yes, it should be the best if you can provide Qemu, kernel .config/ rootfs and simple manual to Daniel how to reach that fault. Thanks, Michal -- 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/