Re: [lwip-users] Problems with ASSERTION in tcp_in and tcp_out

[Justin Bayles]

Hello Leon,

> interesting. Let me ask a few questions before making false assumptions.
> you describe your application as having a read and write process. Do
> they share one instance of lwIP or do they each have an instance of lwIP?

Each process has its own instance of lwIP.

> > I have narrowed in on the source of my problems.
> >
> > When processes send tcp packets and receive ACKs at the same time, the
> >
> What exactly do you mean by "at the same time"? Do you mean the SLIP
> receive thread can be pre-empted by the TCP thread and vice versa.?

I mean that it is possible for tcp_in to be removing PCBs from the unacked 
queue while tcp_enqueue is putting them in. This may not be the problem 
though because I tried wrapping access to the unacked and unsent queues in a 
semaphore and still get the assertion.

All threads are fully preemptable.

> > pcb->snd_queuelen is being corrupted. tcp_out is busy adding PCBs to the
> > send queue in tcp_enqueue() while tcp_in is pulling them out in
> > tcp_receive(). It all depends on who changes the pcb->snd_queuelen first
> > as to whether the process crashes in tcp_in or tcp_out.
> >
> Are you directly calling the tcp_*() functions?

No, I am not directly calling the tcp_*() functions.

> > Is this a problem that other people have experienced? Am I doing
> > something
> > wrong with my implementation.
> >
> Well, at least we should find out what is wrong. In the best case, we
> need to document lwIP better.
>
> Regards,
>
> Leon.

Would it be helpful if I sent you a copy of my sys_arch.c file? You might be 
able to spot an id10t error.
Thanks for persisting with me,
Justin


> > Thanks,
> > Justin
> >
> > >From: "Justin Bayles" <address@hidden>
> > >Reply-To: Mailing list for lwIP users <address@hidden>
> > >To: address@hidden
> > >Subject: Re: [lwip-users] Problems with ASSERTION in tcp_in and tcp_out
> > >Date: Fri, 11 Jun 2004 10:59:33 +1000
> > >
> > >Hi Leon,
> > >
> > >I am using the 0.7.2 release to do a win32 port.
> > >
> > >I am using the slip interface with Named Pipes as the physical layer. 
> Each
> > >netif connects to the Named Pipe Server. The Named Pipe Server is a
> > >separate process that creates a thread to listen to each pipe. When a 
> full
> > >slip packet arrives, the thread transmits the slip packet down every 
> pipe
> > >except the pipe that the packet came from. The write is protected by a
> > >semaphore so that pipes will only ever receive one slip packet at a 
> time.
> > >This has no effect on the lwip stack. It emulates a shared transmission
> > >medium.
> > >
> > >I have a read process that listens for incoming connection requests,
> > >connects, receives data and prints it to stdout. The read process has 
> three
> > >threads running: the tcpip thread, the slipif thread and the main 
> thread.
> > >The tcpip thread is generated by lwip. The slipif thread reads bytes 
> from
> > >the serial interface (pipe), and forwards complete slip packets to the 
> ip
> > >layer. The main thread is an infinite loop on netconn_recv, 
> netbuf_data,
> > >netbuf_delete etc.
> > >
> > >I have a write process that connects to the read process and sends 
> packets
> > >every half a second using netconn_write. The write process also has 
> three
> > >threads running: the tcpip thread, the slipif thread and the main 
> thread.
> > >
> > >Sometime I get up to 250 successful transmissions before the ASSERTION 
> in
> > >tcp_out or tcp_in is called. I think I have a re-entrancy problem.
> > >
> > >Thanks,
> > >Justin
> > >
> > >
> > >
> > >>From: Leon Woestenberg <address@hidden>
> > >>Reply-To: Mailing list for lwIP users <address@hidden>
> > >>To: Mailing list for lwIP users <address@hidden>
> > >>Subject: Re: [lwip-users] Problems with ASSERTION in tcp_in and 
> tcp_out
> > >>Date: Thu, 10 Jun 2004 18:54:00 +0200
> > >>
> > >>Hello Justin,
> > >>
> > >>
> > >>Justin Bayles wrote:
> > >>
> > >>>I am having trouble with the following assertions:
> > >>>
> > >>>"Assertion "tcp_enqueue: valid queue length" failed at line 139 in
> > >>>.\src\core\tcp
> > >>>_out.c"
> > >>>
> > >>>"Assertion "tcp_receive: valid queue length" failed at line 801 in
> > >>>.\src\core\tcp
> > >>>_in.c"
> > >>>
> > >>>Could people please suggest some possible solutions to these errors? 
> I
> > >>>have read previous posts from the archive on this topic however they 
> have
> > >>>not helped.
> > >>>
> > >>Could you mention the version of lwIP you are using? As well as some
> > >>details on your application.
> > >>
> > >>Regards,
> > >>
> > >>Leon.
> > >>
> > >>
> > >>
> > >>_______________________________________________
> > >>lwip-users mailing list
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> > >>http://lists.nongnu.org/mailman/listinfo/lwip-users
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