Re: [lwip-users] lwIP RAW API and "deferred processing" in different context

[Ueli Niederer]

Hello Simon

Thank you for your answer. For me there come a few more question up.

Quoting Simon Goldschmidt <address@hidden>:
> Ueli Niederer <address@hidden> wrote:
> >    - Am I missing something if I wrap every tcp_*-call and the
> > relevant portions of a callback in SYS_ARCH_PROTECT/SYS_ARCH_UNPROTECT
> > calls if I want to cross a context border?
> In your scenario below (where the input and timer processing is  
> effectively locked, already, since it runs in the ISR context that  
> you protect from, I assume), it should suffice to lock interrupts  
> for all calls into the stack (i.e. tcp_write, etc.).
Your assumption is correct: The whole TCP/IP stack runs in the context  
of the ISR which I have to protect against the main loop. In fact  
SYS_ARCH_PROTECT is implemented by disabling the interrupt line to the  
CPU core in TI's Stellaris "NO_SYS" port.

> This assumes that the stellaris netif driver can handle this correctly.
Do you have any possible "incorrect handling" in mind while writing this?

> >    - Is it correct, that pbuf_*-calls and memp_*-calls are already
> > constructed thread-safe?
> Partly. Allocation/deallocation and pbuf_ref() are safe as long as  
> SYS_ARCH_PROTECT is implemented correctly and enabled, they should  
> be safe to use from ISR vs. application level. Other functions like  
> pbuf_header() are not safe, but in your scenario, that should be OK.
Ok, maybe for a easy capsulation it would then be better to protect  
every use of lwIP functions instead of forgetting a function that  
should have been protected, right? So for example it would be  
nescessary to protect a chaining of received pbufs or a call to  
tcp_close should also be protected, etc.

> In general, it would be a better idea to enqueue RX packets for  
> processing at application level, though, so that lwIP runs  
> completely at application level.
I agree with that. Unfortunately my part is only a piece of a bigger  
project which is already implemented on top of TI's port so I don't  
want to take too much risk there by changing everything.

Thank you for your advice.
Ueli