On 2012-01-26 15:55, Gilles Chanteperdrix wrote:
> On 01/26/2012 11:36 AM, Jan Kiszka wrote:
>> On 2012-01-25 19:05, Jan Kiszka wrote:
>>> On 2012-01-25 18:44, Gilles Chanteperdrix wrote:
>>>> On 01/25/2012 06:10 PM, Jan Kiszka wrote:
>>>>> On 2012-01-25 18:02, Gilles Chanteperdrix wrote:
>>>>>> On 01/25/2012 05:52 PM, Jan Kiszka wrote:
>>>>>>> On 2012-01-25 17:47, Jan Kiszka wrote:
>>>>>>>> On 2012-01-25 17:35, Gilles Chanteperdrix wrote:
>>>>>>>>> On 01/25/2012 05:21 PM, Jan Kiszka wrote:
>>>>>>>>>> We had two regressions in this code recently. So test all 6 possible
>>>>>>>>>> SIGDEBUG reasons, or 5 if the watchdog is not available.
>>>>>>>>> Ok for this test, with a few remarks:
>>>>>>>>> - this is a regression test, so should go to
>>>>>>>>> src/testsuite/regression(/native), and should be added to the
>>>>>>>>> xeno-regression-test
>>>>>>>> What are unit test for (as they are defined here)? Looks a bit 
>>>>>>>> inconsistent.
>>>>>> I put under "regression" all the tests I have which corresponded to
>>>>>> things that failed one time or another in xenomai past. Maybe we could
>>>>>> move unit tests under regression.
>>>>>>>>> - we already have a regression test for the watchdog called mayday.c,
>>>>>>>>> which tests the second watchdog action, please merge mayday.c with
>>>>>>>>> sigdebug.c (mayday.c also allows checking the disassembly of the code 
>>>>>>>>> in
>>>>>>>>> the mayday page, a nice feature)
>>>>>>>> It seems to have failed in that important last discipline. Need to 
>>>>>>>> check
>>>>>>>> why.
>>>>>>> Because it didn't check the page content for correctness. But that's now
>>>>>>> done via the new watchdog test. I can keep the debug output, but the
>>>>>>> watchdog test of mayday looks obsolete to me. Am I missing something?
>>>>>> The watchdog does two things: it first sends a SIGDEBUG, then if the
>>>>>> application is still spinning, it sends a SIGSEGV. As far as I
>>>>>> understood, you test tests the first case, and mayday tests the second
>>>>>> case, so, I agree that mayday should be removed, but whatever it tests
>>>>>> should be integrated in the sigdebug test.
>>>>> Err... SIGSEGV is not a feature, it was the bug I fixed today. :) So the
>>>>> test case actually specified a bug as correct behavior.
>>>>> The fallback case is in fact killing the RT task as before. But I'm
>>>>> unsure right now: will this leave the system always in a clean state
>>>>> behind?
>>>> The test case being a test case and doing nothing particular, I do not
>>>> see what could go wrong. And if something goes wrong, then it needs fixing.
>>> Well, if you kill a RT task while it's running in the kernel, you risk
>>> inconsistent system states (held mutexex etc.). In this case the task is
>>> supposed to spin in user space. If that is always safe, let's implement
>>> the test.
>> Had a closer look: These days the two-stage killing is only useful to
>> catch endless loops in the kernel. User space tasks can't get around
>> being migrated on watchdog events, even when SIGDEBUG is ignored.
>> To trigger the enforced task termination without leaving any broken
>> states behind, there is one option: rt_task_spin. Surprisingly for me,
>> it actually spins in the kernel, thus triggers the second level if
>> waiting long enough. I wonder, though, if that behavior shouldn't be
>> improved, ie. the spinning loop be closed in user space - which would
>> take away that option again.
>> Thoughts?
> You can also call in an infinite loop, a xenomais syscall which causes a
> switch to primary mode, but fails.

Nope, we would be migrated to secondary on xnthread_amok_p when
returning to user mode. We need a true kernel loop.


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