[ECOS] ecos + lwip

Mandeep Sandhu mandeepsandhu.chd@gmail.com
Thu Sep 3 08:46:00 GMT 2009

On Thu, Sep 3, 2009 at 2:22 PM, Simon Kallweit<simon.kallweit@intefo.ch> wrote:
> Mandeep Sandhu wrote:
>>>>> <snip>
>>>>> cyg_lwip_sequential_init();
>>>>> cyg_lwip_thread_new( "My thread", m_main, (void *)"My thread",
>>>>> my_stack, 0x1000, 5 );
>>>>> ...
>>>>> ...
>>>>> <snip>
>>>>> I'll enable more debugs to see where it's getting stuck.
>>>> After changing it to 2, it's able to find the interface (et0) with all
>>>> the right settings.
>>> Well, that does not really make sense. cyg_lwip_sequential_init() will
>>> not
>>> return until the lwip stack is initialized, and initializing ethernet
>>> device
>>> drivers is part of that. This *must* work even when the TCPIP thread has
>>> lower priority, as long as you start your application thread *after* the
>>> execution of cyg_lwip_sequential_init(). By starting *after* I mean that
>>> you
>>> also have to make sure that cyg_lwip_sequential_init() and starting your
>>> applications thread is done in the same thread!
>>> I hope I didn't miss the obvious here, but that's how it should work.
>> Well, I checked the code again. The netif init is done as part of
>> tcpip_init_done().
>> This I see is being called in tcpip_thread(). This function is being
>> executed in the
>> tcpip thread's context.
>> I guess this is why the priority of the threads matters.
>> Would do you think?
> There is a semaphore created in cyg_lwip_sequential_init() which will block
> until all initialization (including ethernet devices) in the tcpip thread is
> done. Therefore it's priority does not matter. cyg_lwip_sequential_init()
> should not return before initialization is completed.
> I just reviewed the code and found that the semaphore is initialized with 1,
> which is clearly a bug, it should be initialized with 0 so that the
> following call to cyg_semaphore_wait() is actually blocking the thread until
> initialization is done.
> My mistake, sorry! Hope it works as intended now. New release:
> http://download.westlicht.ch/lwip-20090903.tar.gz

Thanks Simon. I totally missed the sem init part...i guess since the sem is
init to 1...the thread never actually waits...and thats why I was seeing the

I'll try out the new build and let you know...


> Simon

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