Re: [Xenomai] I-Pipe Tracer and linux ftrace

[Jan Kiszka <jan.kiszka@siemens.com>]

On 2015-06-23 16:41, Antoine Durand wrote:
> The clocksource switching is due to the config option
> 
> CONFIG_NR_CPUS=2
> 
> the CPU is quad core and i would like to use only two of them to emulate a
> cheaper board.
> 
> now the time run normally

Interesting. Maybe the kernel parameter maxcpus works better (it is
definitely more handy).

Jan

> 
> i will check if the other problems are resolved.
> 
> Thanks
> 
> 
> 2015-06-23 16:27 GMT+02:00 Gilles Chanteperdrix <
> gilles.chanteperdrix@xenomai.org>:
> 
>>
>> Jan Kiszka wrote:
>>> On 2015-06-23 16:11, Lennart Sorensen wrote:
>>>> On Tue, Jun 23, 2015 at 12:09:09PM +0200, Antoine Durand wrote:
>>>>> I found a new problem that must be the root cause of the others (I
>>>>> hope)
>>>>> the linux system time is wrong, one second last 31 real seconds !
>>>>>
>>>>> ftrace timing are wrong and may be nmi watchdog is fired because of
>>>>> that
>>>>> wrong time too.
>>>>>
>>>>> however the time run normally in /proc/driver/rtc
>>>>> (the CPU board get a Dallas DS12887 / Motorola MC146818 compatible RTC)
>>>>
>>>> Normally the RTC is only used to get time at boot and save it when the
>>>> system is off.  It usually has nothing at all to do with system time
>>>> while the system is running.
>>>>
>>>> So having the rtc correct but system time wrong is perfectly plausible
>>>> if whatever is used for system time is broken.
>>>>
>>>>> I use the CLOCK_MONOTONIC clock in xenomai periodic task and it works
>>>>> well.
>>>>> I-Pipe tracer timing are correct too.
>>>>>
>>>>> in /proc/interrupts :
>>>>> IRQ0 (timer) counter is not counting
>>>>> LOC (local timer interrupts) is counting
>>>>>
>>>>> in /proc/xenomai/irq :
>>>>> [timer/0] is counting (following LOC value)
>>>>>
>>>>> I'm trying to find why IRQ0 never happen.
>>>>
>>>> Are you running NO_HZ config?
>>>>
>>>
>>> Huh, that would be interesting...
>>>
>>> Also check your Linux clocksource
>>> (/sys/devices/system/clocksource/clocksource0/current_clocksource). It
>>> should be TSC on sane systems. If not, check the kernel log for
>>> clocksource switches and related reason reports.
>>
>> Using another clocksource than TSC should not be a problem, neither for
>> Linux, nor for Xenomai. That said I have not tested this in a long time.
>>
>> --
>>                                             Gilles.
>> https://click-hack.org
>>
>>
> 

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