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

From: Sylvain Rochet
Subject: Re: [lwip-users] Infinite hang in tcp_slowtmr()
Date: Tue, 13 Oct 2015 10:15:42 +0200
User-agent: Mutt/1.5.21 (2010-09-15)

Hi Stephen,

On Mon, Oct 12, 2015 at 04:59:19PM -0500, Stephen Cowell wrote:
> On 10/12/2015 3:41 PM, Sylvain Rochet wrote:
> >
> > 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.

But there are probably interrupts, which is even worse. Could you first 
check that no lwIP functions are called in interrupts contexts ? 
Probably around the macb driver.

If I have time I will fetch the Atmel port for SAM4E/bare-metal and 
take a short look at it.

> 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

Port/mutex/IRQ issues there as well. Linked list are very sensitive to 
context violation.

> It looks like this code has had many bugs and problems...

Thanks ! :)


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