On 10/15/2014 03:12 PM, ZIV-Alberto Ozalla Cantabrana wrote:
>
> On 15/10/14 13:11, Gilles Chanteperdrix wrote:
>> On 10/15/2014 12:59 PM, ZIV-Alberto Ozalla Cantabrana wrote:
>>> Dear colleagues,
>>>
>>> I face an unexpected switch to secondary mode after the very first call to
>>> rt_timer_tsc() into a real-time task created by Xenomai.
>>> This unexpected switch only arises if it is the very first call to
>>> rt_timer_tsc().
>> Hi,
>>
>> I see two possible reasons for that:
>> - either on-demand mapping of library text page
>> - or first access to the hardware register.
>>
>> In order to find which is the reason.
>>
>> Could you replace the call to rt_timer_tsc() with a call to __xn_rdtsc()
>> after including asm/xenomai/tsc.h ?
>>
>>
> Hello,
>
> Thanks for the fast response.
>
> Unfortunately replacing the call to rt_timer_tsc() with a call to
> __xn_rdtsc() does not solve the problem.
The intent was not to solve the problem, but to investigate it.
>
> Another clue is that PF value increases at the same time as MSW.
>
>
> CPU PID MSW CSW PF STAT %CPU NAME
> 0 0 0 11594571 0 00500080 96.3 ROOT/0
> 0 1690 1 5339 1 00300184 1.0 Test_Task
>
> It seems to be a first access to the hardware register.
It would seem so. I will prepare a piece of code tonight that does not
rely on any external symbol, just to be sure.
>
> Note: I use a call to mlockall(MCL_CURRENT|MCL_FUTURE) before creating
> the task.
I do not believe mlockall applies to register mapped from /dev/mem, only
to memory mappings
--
Gilles.
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