Re: Kernel Oops

On 04/04/2016 09:35 AM, Bunjes Friedemann wrote:
>>> I disabled the high precision timer in my bios and recompiled a 
>>> fresh patched 3.16 kernel not in preemtible, but in desktop mode.
>>> Now the module seems to load, but the latency test hangs due to a 
>>> non-responding module (?):
>>>
>> Do not stay hanged on a single task. Try the user latency also and 
>> report.
>> Paolo
>
> Hi,
>
> sorry, I do not understand.
> Is the testsuite/kern/latency not supposed to work?
>
It must work. In fact I assumed that you were testing in user space and 
asked to check kernel space also.

Paolo
> -Friedemann
>
>>
>>> [   74.567982] RTAI[malloc]: global heap size = 2097152 bytes, <BSD>.
>>> [   74.595871] , kstacks pool size = 524288 bytes.
>>> [   74.595873] RTAI[sched]: hard timer type/freq = 
>>> APIC/99748998(Hz); default timing: periodic; linear timed lists.
>>> [   74.595875] RTAI[sched]: Linux timer freq = 250 (Hz), TimeBase 
>>> freq = 3191992000 hz.
>>> [   74.595877] RTAI[sched]: timer setup = 10 ns, resched latency = 
>>> 3933 ns.
>>>
>>> *
>>> *
>>> * Type ^C to stop this application.
>>> *
>>> *
>>> Warning: Error opening /proc/rtai/latency_calibrate
>>>          Couldn't get infos about the module's state.
>>> RTAI Testsuite - KERNEL latency (all data in nanoseconds)
>>> RTH|    lat min|    ovl min|    lat avg|    lat max|    ovl max|   
>>> overruns
>>>
>>>
>>> What might be the reason for this and how can I debug?
>>>
>>> Cheers,
>>>
>>> Friedemann
>>>
>>>> Am 30.03.2016 um 23:55 schrieb Paolo Mantegazza 
>>>> <[email protected] <mailto:[email protected]>>:
>>>>
>>>> Unfortunately this thread went on privately. Likely because of a 
>>>> wrong answer click of mine, apologies.
>>>>
>>>> In any case it gives me the chance of remarking a few things 
>>>> related to the support of Linux-3.x.x and now 4.x.x.
>>>> - RTAI-4 onward) is based on the oneshot mode timing only. I still 
>>>> use periodic timers on data acquisition card to time specific tasks 
>>>> . whituout charging the scheduler with their pacing.
>>>> - from RTAI-5, i.e the actual VULCANO to be released shortly, 
>>>>  there starting/stopping_rt_timer, it is done by rtai_sched onyhow.
>>>> - in such a view the setting of the hard timer mode its start/stop, 
>>>> both in periodic and oneshot mode, will do nothing; they are just 
>>>> kept for compatibility, so that there is no need to change any 
>>>> existing code
>>>> - HPET is not used by RTAI but 8259/54 is used in UP mode, even if 
>>>> it is strongly suggested to enable the APIC if available
>>>> - RTAI does not use the second channel of 8259/54 to emulate a 
>>>> continuously running clock, so  a _TSC_is_needed
>>>>
>>>> In practice what above restricts the newest RTAI versions to true 
>>>> 586s and onward. For fake 586s and 486 earlier version of RTAI 
>>>> should be used.
>>>>
>>>> That said there is no need to disable NO_HZ and high 
>>>> precision/resolution timers if they are available in Linux.
>>>>
>>>> Paolo
>>>>
>>>> ________________________________________
>>>> From: Rtai [[email protected] <mailto:[email protected]>] 
>>>> on behalf of Alec Ari [[email protected] 
>>>> <mailto:[email protected]>]
>>>> Sent: Wednesday, March 30, 2016 10:37 PM
>>>> To: RTAI Mailing List
>>>> Subject: Re: [Rtai] Kernel Oops
>>>>
>>>> RTAI should be able to use the 8259/8254 timers unless that's now 
>>>> broken? It's never _needed_ APIC or HPET in the past. If it's 
>>>> broken or not working (buggy hardware / BIOS) try disabling high 
>>>> precision + high resolution event timers in kernel config and BIOS 
>>>> if applicable. Also, to avoid NULL pointer issues, set 
>>>> CONFIG_LSM_MMAP_MIN_ADDR to value 65536.
>>>>
>>>> Alec Ari
>>>> _______________________________________________
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>>>
>>> -- 
>>> Dr. rer. nat. Friedemann Bunjes
>>> EDV Entwicklung und Koordination
>>> Hertie-Institut für Klinische Hirnforschung
>>> Zentrum für Neurologie
>>> Universitätsklinikum Tübingen
>>> Otfried-Müller-Str. 25
>>> 72076 Tübingen
>>> Tel. +49-7071-29-81999
>>> Fax +49-7071-29-25010
>>>
>>
>
> -- 
> Dr. rer. nat. Friedemann Bunjes
> EDV Entwicklung und Koordination
> Hertie-Institut für Klinische Hirnforschung
> Zentrum für Neurologie
> Universitätsklinikum Tübingen
> Otfried-Müller-Str. 25
> 72076 Tübingen
> Tel. +49-7071-29-81999
> Fax +49-7071-29-25010
>

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