Re: [lwip-users] Help with LwIP Modem

[Jaime Fernandez Hoffiz]

Thanks Jeff, Simon, Sylvain, 

Please bear with me since I'm a little bit out of my comfort zone. 

Sylvian first suggestion is to not called tcpip_input from the interrupt and provided a suggestion that is probably safer in the case of SYSBIOS having or not a different context between ISR and other threads. I would try to implement this change as it sounds it will be safer in either OS type. I did a little research and SYSBIOS (TI kernel) there is no distinction between hwi (isrs), swi, tasks, etc. Seems like it treats everything in the same context.I could be wrong.

Simon, thanks, I already made that change to the port. Instead of calling the "input function" directly I call "return netif->input(p, netif);".

On the other hand I think the port is not calling tcpip_input from the ISR context, I will still implement the change to eliminate some variables. This is how I start my code in SYSBIOS:

(these are what I think are the relevant pieces to the conversation)

1.     task = Task_create( (Task_FuncPtr) echo_thread, NULL, &eb);
   
2. tcpip_init(echo_init, &init_sem);
   

On Fri, Jul 8, 2016 at 12:29 PM, Jeff Barlow <address@hidden> wrote:

On 07/08/2016 05:23 AM, Simon Goldschmidt wrote:

I know what's behind technically, with that question I'd rather meant what's the big deal for an OS
to make this difference? It knows about which task is currently running and which got runnable,
so it's not a big deal to know it's in interrupt context. From all the embedded OSes I've used so far,
FreeRTOS is the only one to make this difference.

And in my view, passing the "fromISR" around up to portions of the code that should be independent
of whether run from task or from ISR sometimes makes the code design worse.

I think you will find that ChibiOS does much the same. The reasoning as I understand it is to keep ISR code paths as short as possible to minimize latency in hard real time systems.
--
Later,
Jeff

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