Re: [Xenomai-core] Realtime gettimeofday()

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

Wolfgang Mauerer wrote:
> Hi,
> 
> On 03.12.2009, at 14:14, Gilles Chanteperdrix <gilles.chanteperdrix@xenomai.org 
>  > wrote:
> 
>> Wolfgang Mauerer wrote:
>>> Hi,
>>>
>>> Gilles Chanteperdrix wrote:
>>>> Wolfgang Mauerer wrote:
>>>>> So that means, in essence, that you would accept probabilistic
>>>>> algorithms in realtime context?
>>>> Ah, today's troll!
>>> though it seems that I have to replace Jan this time ;-)
>>>> As I think I explained, the use of a seqlock in real-time context  
>>>> when
>>>> the seqlock writer only happens in linux context is not  
>>>> probabilistic.
>>>> It will work every time the first pass.
>>> I still don't see why it should succeed every time: What about
>>> the case that the Linux kernel on CPU0 updates the data, while
>>> Xenomai accesses them on another CPU? This can lead to
>>> inconsistent data, and they must be reread on the Xenomai side.
>> Yeah, right. I was not thinking about SMP. But admit that in this  
>> case,
>> there will be only one retry, there is nothing pathological.
>>
>>> I'm asking because if this case can not happen, then there's
>>> nothing left to to as I have the code already at hand.
>> You have reworked the nucleus timers handling to adapt to this new
>> real-time clock ?
> 
> Nope. Sorry, I was a bit unclear: I'm just referring to the gtod  
> syscall that does the timer handling, Not any other adaptions.

Ok, but what good is the gtod syscall if you can not use it as a time
reference for other timing related services?

-- 
                                          Gilles