On 2011-05-25 14:19, Gilles Chanteperdrix wrote:
> On 05/25/2011 02:12 PM, Jan Kiszka wrote:
>> On 2011-05-25 13:58, Gilles Chanteperdrix wrote:
>>> On 05/25/2011 01:20 PM, Jan Kiszka wrote:
>>>> On 2011-05-24 16:03, Gilles Chanteperdrix wrote:
>>>>> On 05/24/2011 03:52 PM, Jan Kiszka wrote:
>>>>>> On 2011-05-24 14:30, Gilles Chanteperdrix wrote:
>>>>>>>>>>>> Do you already have an idea how to get that info to the delete hook
>>>>>>>>>>>> function?
>>>>>>>>>>> Yes. We start by not applying the list reversal patch, then the 
>>>>>>>>>>> sys_ppd
>>>>>>>>>>> is the first in the list. So, we can, in the function ppd_remove_mm,
>>>>>>>>>>> start by removing all the others ppd, then remove the sys ppd (that 
>>>>>>>>>>> is
>>>>>>>>>>> the first), last. This changes a few signatures in the core code, a 
>>>>>>>>>>> lot
>>>>>>>>>>> of things in the skin code, but that would be for the better...
>>>>>>>>>> I still don't see how this affects the order we use in
>>>>>>>>>> do_taskexit_event, the one that prevents xnsys_get_ppd usage even 
>>>>>>>>>> when
>>>>>>>>>> the mm is still present.
>>>>>>>>> The idea is to change the cleanup routines not to call xnsys_get_ppd.
>>>>>>>> ...and use what instead? Sorry, I'm slow today.
>>>>>>> The sys_ppd passed as other argument to the cleanup function.
>>>>>> That would affect all thread hooks, not only the one for deletion. And
>>>>>> it would pull in more shadow-specific bits into the pod.
>>>>>> Moreover, I think we would still be in troubles as mm, thus ppd,
>>>>>> deletion takes place before last task deletion, thus taskexit hook
>>>>>> invocation. That's due to the cleanup ordering in the kernel's do_exit.
>>>>>> However, if you have a patch, I'd be happy to test and rework my leakage
>>>>>> fix.
>>>>> I will work on this ASAP.
>>>> Sorry for pushing, but I need to decide if we should role out my
>>>> imperfect fix or if there is chance to use some upstream version
>>>> directly. Were you able to look into this, or will this likely take a
>>>> bit more time?
>>> I intended to try and do this next week-end. If it is more urgent than
>>> that, I can try in one or two days. In any case, I do not think we
>>> should try and workaround the current code, it is way to fragile.
>> Mmh, might be true. I'm getting the feeling we should locally revert all
>> the recent MPS changes to work around the issues. It looks like there
>> are more related problems sleeping (we are still facing spurious
>> fast-synch related crashes here - examining ATM).
> This is the development head, it may remain broken for short times while
> we are fixing. I would understand reverting on the 2.5 branch, not on -head.

I was thinking loudly about our (Siemens) local branch, not -head. We
are forced to use head to have features like automatic non-RT shadow

>> Another thing that just came to my mind: Do we have a well-defined
>> destruction order of native skin or native tasks vs. system skin? I mean
>> the latter destroys the local sem_heap while the former may purge
>> remaining native resources (including the MPS fastlock). I think the
>> ordering is inverted to what the code assumes (heap is destructed before
>> the last task), no?
> IMO, the system skin destroy callback should be called last, this should
> solve these problems. This is what I was talking about.

OK. Still, tasks aren't destroyed on mm shoot-down but via a dedicated
do_exit callback that is invoke by the kernel a few instructions later.
Nothing we can directly influence from Xenomai code.


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