On 01/26/2012 04:06 PM, Jan Kiszka wrote:
> 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.
But the loop will continue, and the next call to the syscall will cause
the thread to re-switch to primary mode.
--
Gilles.
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