Re: [Xenomai-help] rt_queue_write return 1, with no receiver

[Philippe Gerum <rpm@xenomai.org>]

Mark Saiia wrote:
> With the debugging options enabled, at the point when the application
> has previously shifted from 1 waiter to 2 waiters, the system
> hardlocks, just as when I was catting the queue proc entry.
>

That is expected, but what does the kernel log say at that point?

> On 3/10/09, Philippe Gerum <rpm@xenomai.org> wrote:
>> Mark Saiia wrote:
>>> When our app's log shows the number of waiters is 1(via
>>> rt_queue_inquire), catting the proc entry shows the queue info, and a
>>> + on the next line.  However, when the log shows the number of waiters
>>> is 2, catting the proc entry crashes the system hard, which
>>> necessitates a reboot.  This behavior is completely reproducible.
>>>
>> This is an evidence that some internal data structures are terminally
>> broken.
>> You may want to enable CONFIG_XENO_OPT_DEBUG, CONFIG_XENO_OPT_DEBUG_NUCLEUS
>> and
>> CONFIG_XENO_OPT_DEBUG_QUEUES in your kernel config. The nucleus will pull
>> the
>> break when a corruption is detected at runtime.
>>
>>> Mark
>>>
>>>
>>> On 3/10/09, Philippe Gerum <rpm@xenomai.org> wrote:
>>>> Steven Seeger wrote:
>>>>>> Yes, the docs are correct, and the code looks sane as well. You may
>>>>>> want to
>>>>>> double-check your findings using rt_queue_inquire() before calling
>>>>>> rt_queue_write(), even if this won't be 100% reliable in case your
>>>>>> reader is
>>>>>> polling the queue.
>>>>> Philippe,
>>>>>
>>>>> We took your advice and tried rt_queue_inquire(). If we use a timeout on
>>>>> the read, It seems there are always 3 waiters, which is strange because
>>>>> we have only one thread reading from the queue. If we remove the timout,
>>>>> there is either 1 or 2 waiters. It got 0 waiters once and still hung.
>>>>> Very strange.
>>>>>
>>>> /proc/xenomai/registry/native/queues/* will tell you which threads are
>>>> pending
>>>> on the queue.
>>>>
>>>>> Thanks,
>>>>> Steven
>>>>>
>>>>>
>>>> --
>>>> Philippe.
>>>>
>>
>> --
>> Philippe.
>>
> 


-- 
Philippe.