Re: [lwip-users] Infinite hang in tcp_slowtmr()

[Stephen Cowell]

On 10/12/2015 3:41 PM, Sylvain Rochet wrote:
> Hi Stephen,
>
> On Mon, Oct 12, 2015 at 02:51:14PM -0500, Stephen Cowell wrote:
> > I find that I sometimes get an infinite loop when stepping to
> > pcb->next...
> I didn't have to read further. As usual, it looks like a broken port or
> usage which violate lwIP threading model.
>
> Summary:
>
> - Do *NOT* call anything in interrupt context, nothing, never,
> absolutely never, use your OS semaphore signaling to an
> Ethernet/serial/… RX thread

I don't think I'm doing that, Sylvain... this is non-OS, so there
are no 'threads'.   Atmel wrote the port.  I'm running sntp and ftpd, they
hook in using their own _init() routines that have not been
modified.

Here's more links describing the problem:

http://savannah.nongnu.org/bugs/?45433
https://lists.gnu.org/archive/html/lwip-users/2004-10/msg00033.html

"

Why would a pcb->next pointer end up pointing to itself (pcb)?

"

Indeed... that's the whole problem.  I solved my problem with a hack that
nobody gets to see here... not sure why.

It looks like this code has had many bugs and problems... I'm glad I could
at least fix my issue.  I won't bother you with any more, since obviously
I'm not making it to the main list.
__
Steve
.

> - memp_*, pbuf_*, functions are thread-safe if SYS_LIGHTWEIGHT_PROT is
> set, and again, thread safe does not mean it is interrupt safe
>
> - Do *NOT* call any function from the RAW API outside lwIP thread
>
> - Use Netconn or Socket API in others threads, but keep in mind you
> should not share a Netconn/Socket control block between threads, (or use
> proper locking if you really have to, of course).
>
> - Please read doc/rawapi.txt from the lwIP source which explain that
> more comprehensively
>
> Sylvain
>
>
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