Re: [Xenomai-core] Potential problem with rt_eepro100

[Jan Kiszka <jan.kiszka@domain.hid>]

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Am 01.11.2010 17:55, Anders Blomdell wrote:
> Jan Kiszka wrote:
>> Am 28.10.2010 11:34, Anders Blomdell wrote:
>>> Jan Kiszka wrote:
>>>> Am 28.10.2010 09:34, Anders Blomdell wrote:
>>>>> Anders Blomdell wrote:
>>>>>> Anders Blomdell wrote:
>>>>>>> Hi,
>>>>>>>
>>>>>>> I'm trying to use rt_eepro100, for sending raw ethernet packets,
>>>>>>> but I'm
>>>>>>> experincing occasionally weird behaviour.
>>>>>>>
>>>>>>> Versions of things:
>>>>>>>
>>>>>>>   linux-2.6.34.5
>>>>>>>   xenomai-2.5.5.2
>>>>>>>   rtnet-39f7fcf
>>>>>>>
>>>>>>> The testprogram runs on two computers with "Intel Corporation
>>>>>>> 82557/8/9/0/1 Ethernet Pro 100 (rev 08)" controller, where one
>>>>>>> computer
>>>>>>> acts as a mirror sending back packets received from the ethernet
>>>>>>> (only
>>>>>>> those two computers on the network), and the other sends packets and
>>>>>>> measures roundtrip time. Most packets comes back in approximately
>>>>>>> 100
>>>>>>> us, but occasionally the reception times out (once in about 100000
>>>>>>> packets or more), but the packets gets immediately received when
>>>>>>> reception is retried, which might indicate a race between
>>>>>>> rt_dev_recvmsg
>>>>>>> and interrupt, but I might miss something obvious.
>>>>>> Changing one of the ethernet cards to a "Intel Corporation 82541PI
>>>>>> Gigabit Ethernet Controller (rev 05)", while keeping everything else
>>>>>> constant, changes behavior somewhat; after receiving a few 100000
>>>>>> packets, reception stops entirely (-EAGAIN is returned), while
>>>>>> transmission proceeds as it should (and mirror returns packets).
>>>>>>
>>>>>> Any suggestions on what to try?
>>>>> Since the problem disappears with 'maxcpus=1', I suspect I have a SMP
>>>>> issue (machine is a Core2 Quad), so I'll move to xenomai-core.
>>>>> (original message can be found at
>>>>> http://sourceforge.net/mailarchive/message.php?msg_name=4CC82C8D.3080808%40control.lth.se
>>>>>
>>>>> )
>>>>>
>>>>> Xenomai-core gurus: which is the corrrect way to debug SMP issues?
>>>>> Can I run I-pipe-tracer and expect to be able save at least 150 us of
>>>>> traces for all cpus? Any hints/suggestions/insigths are welcome...
>>>> The i-pipe tracer unfortunately only saves traces for a the CPU that
>>>> triggered the freeze. To have a full pictures, you may want to try my
>>>> ftrace port I posted recently for 2.6.35.
>>> 2.6.35.7 ?
>>>
>>
>> Exactly.
> Finally managed to get the ftrace to work
> (one possible bug: had to manually copy
> include/xenomai/trace/xn_nucleus.h to
> include/xenomai/trace/events/xn_nucleus.h), and it looks like it can be
> very useful...
> 
> But I don't think it will give much info at the moment, since no
> xenomai/ipipe interrupt activity shows up, and adding that is far above
> my league :-(

You could use the function tracer, provided you are able to stop the
trace quickly enough on error.

> 
> My current theory is that the problem occurs when something like this
> takes place:
> 
>   CPU-i        CPU-j        CPU-k        CPU-l
> 
> rt_dev_sendmsg
>         xmit_irq
> rt_dev_recvmsg            recv_irq

Can't follow. When races here, and what will go wrong then?

> 
> So now I'll try to instrument the code to see if the assumtion holds.
> Stay tuned...
> 
> Regards
> 
> Anders
> 
> 

Jan


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