Re: [lwip-users] Reentrency problem within mem.c module

[address@hidden]

Jonathan Larmour schrieb:
> I think doing a tcpip_callback() call (or something similar), so the tcpip
> thread handles it, would be smaller and simpler. (Of course for NO_SYS==1,
> you can just call pbuf_free directly since there should only be one context
> in lwIP as it is).
>   
That's the problem: you can't simply call pbuf_free directly because you 
could be sending a packet at non-interrupt level while trying to free a 
pbuf at TX interrupt level!

For NO_SYS==0, I favour your tcpip_callback since the interrupt function 
doesn't need to walk the heap and thus is faster. But I would favour a 
solution that solves this problem for both NO_SYS settings...

> Perhaps pbuf_free() is a sufficiently common operation for this sort of
> thing, that we could make a new pbuf_free_safe() call or something, which
> either calls pbuf_free() (NO_SYS==1) or tcpip_callback to call pbuf_free
> (NO_SYS==0).
>   
pbuf_free_safe() would be enough in this situation, but since memp_free 
is the problem (no pbuf_free()),
I think memp_free_safe() would be better since it is more generic.

Simon