Re: [Xenomai] OMAP L138

[Gilles Chanteperdrix <gilles.chanteperdrix@xenomai.org>]

On 04/23/2014 03:45 AM, Peter Howard wrote:
> On Wed, 2014-04-23 at 01:02 +0200, Gilles Chanteperdrix wrote:
>> On 04/15/2014 11:59 PM, Peter Howard wrote:
>>> On Tue, 2014-04-15 at 13:37 +0200, Gilles Chanteperdrix wrote:
>>>> On 04/15/2014 08:03 AM, Peter Howard wrote:
>>>>> On Fri, 2014-04-11 at 08:52 +1000, Peter Howard wrote:
>>>>>> On Fri, 2014-04-11 at 00:48 +0200, Gilles Chanteperdrix wrote:
>>>>>>> On 04/11/2014 12:34 AM, Peter Howard wrote:
>>>>>>>> On Fri, 2014-04-11 at 00:23 +0200, Gilles Chanteperdrix wrote:
>>>>>>>> (Stripping back conversation on this one - apologies if that's bad
>>>>>>>> etiquette for this list)
>>>>>>>>  
>>>>>>>>> Attachment is better. Also please post the changes you made for omapL138
>>>>>>>>>
>>>>>>>>
>>>>>>>> diff --git a/arch/arm/mach-davinci/Kconfig b/arch/arm/mach-davinci/Kconfig
>>>>>>>> index a075b3e..3d8bc59 100644
>>>>>>>> --- a/arch/arm/mach-davinci/Kconfig
>>>>>>>> +++ b/arch/arm/mach-davinci/Kconfig
>>>>>>>> @@ -41,6 +41,8 @@ config ARCH_DAVINCI_DA850
>>>>>>>>  	select ARCH_DAVINCI_DA8XX
>>>>>>>>  	select ARCH_HAS_CPUFREQ
>>>>>>>>  	select CP_INTC
>>>>>>>> +    select IPIPE_ARM_KUSER_TSC if IPIPE
>>>>>>>> +    select ARM_FCSE if IPIPE
>>>>>>>
>>>>>>> You may want to leave the choice of enabling or disabling FCSE to the user.
>>>>>>>
>>>>>>
>>>>>> Understood; at the moment the variance on max latency is really bad if
>>>>>> you don't enable FCSE.  When I sort out the crashing issues I'll re-test
>>>>>> with it off.
>>>>>
>>>>> Well, FCSE turned out to be my problem.
>>>>>
>>>>> More specifically,  FCSE and ARM_FCSE_BEST_EFFORT.  Either a) disabling
>>>>> ARM_FCSE altogether, or b) selecting ARM_FCSE with ARM_FCSE_GUARENTEED
>>>>> gets rid of the crashes/panics with ipipe latency tracing enabled.
>>>>>
>>>>> So now things seem reasonably stable, I'll go through the full set of
>>>>> tests.  Though I still can't do 'xeno-test -l "dohell -l /opt/ltp"' as
>>>>> ltp takes out the system without any ipipe/xenomai bits.
>>>>>
>>>> Ok, FCSE best effort is currently being validated on 3.14, so it may
>>>> well be broken. After all, the raw/* branches are work in progress.
>>>>
>>>
>>> Note: selecting ARM_FCSE_BEST_EFFORT produces the same result on the
>>> master branch too . . .
>>>
>> Hi Peter,
>>
>> I am unable to reproduce these issues with 3.14, FCSE seems to be doing
>> just fine, I can boot and run the LTP testsuite and get almost the same
>> results as a non patched kernel. I have tried with and without
>> preemptible cache flushes, and with and without Xenomai. My rootfs is
>> based on busybox and minimal, maybe that is the reason why it works
>> fine, could you put a tarball with your rootfs somewhere?
> 
> A bit of testing shows (at least) one case is directly related to the
> rootfs.  This is the Texas Instruments rootfs that is supplied for the
> DA850 board.  During normal startup, it wants to start the GUI for the
> LCD which would go past the 32MB process limit with FCSE enabled.  With
> FCSE_GUARENTEED selected this is noted but doesn't cause a crash.  With
> FCSE_BEST_EFFORT selected this is noted and then the system crashes
> within a few seconds. 

With FCSE_GUARANTEED the system refuses processes to go above the 32MB
limit, so, the program probably does not even start. With
FCSE_BEST_EFFORT, processes should be allowed to go above 32MB.

 I'm not sure if this counts as a bug in
> BEST_EFFORT or whether all bets are off if you try to start a process
> that's too large.

It is supposed to work.

> 
> At this point I'm not sure if anything else is specific to that rootfs
> but I'll still make it available to you to have a look.
> 
> 
Yes, please make it available if that is possible.

Regards.

-- 
                                                                Gilles.