Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756300Ab3HFMaA (ORCPT ); Tue, 6 Aug 2013 08:30:00 -0400 Received: from mail-wi0-f172.google.com ([209.85.212.172]:47731 "EHLO mail-wi0-f172.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754992Ab3HFM37 (ORCPT ); Tue, 6 Aug 2013 08:29:59 -0400 Message-ID: <5200EC4C.5090202@linaro.org> Date: Tue, 06 Aug 2013 14:30:04 +0200 From: Daniel Lezcano User-Agent: Mozilla/5.0 (X11; Linux i686; rv:17.0) Gecko/20130510 Thunderbird/17.0.6 MIME-Version: 1.0 To: Michal Simek CC: =?UTF-8?B?U8O2cmVuIEJyaW5rbWFubg==?= , Stuart Menefy , Stephen Boyd , John Stultz , Thomas Gleixner , Russell King , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org 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: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 9338 Lines: 203 On 08/06/2013 11:18 AM, Michal Simek wrote: > 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. I tried to download qemu for zynq but it fails: git clone git://git.xilinx.com/qemu-xarm.git Cloning into 'qemu-xarm'... fatal: The remote end hung up unexpectedly I am also looking for the option specified for the kernel: "The kernel needs to be built with this feature turned on (in menuconfig, System Type->Xilinx Specific Features -> Device Tree At Fixed Address)." ... but I was not able to find it. any ideas ? Thanks -- Daniel ps : apart that, well documented website ! -- Linaro.org │ Open source software for ARM SoCs Follow Linaro: Facebook | Twitter | Blog -- 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/