Re: [lwip-users] tcpip thread gets stuck when socket is closed

[Stefan Lankes]

Currently, I found the bug. It was a stupid typo in my file sys_arch.c My 
function sys_arch_mbox_tryfetch returned sometimes a wrong value…

Many thanks for your support!

Stefan


> On Sat, 2011-09-17 at 15:51 +0200, Stefan Lankes wrote:
>> 
>>> 
>>> On 15 Sep 2011, at 15:43, Stefan Lankes wrote:
>>> 
>>>> we use LwIP 1.4.0 as TCP/IP stack for an internal OS project. We have 
>>>> already tested some applications, which used the LwIP's Socket API - they 
>>>> work fine. However, if the applications close the socket, the tcpip thread 
>>>> gets stuck and isn't able to handle incoming messages. To analyze this 
>>>> behavior, we defined the macro LWIP_TCPIP_THREAD_ALIVE to print some 
>>>> messages periodically on the screen. This stops by closing the socket. 
>>>> 
>>>> Do you have any idea, why the Socket API doesn't work correctly?
>>> 
>>> You've probably violated lwIP's threading constraints and corrupted some 
>>> internal state such that the tcpip thread gets stuck in a loop.  If you can 
>>> describe all the different threads you have and how they interface to lwIP 
>>> that would probably reveal the problem.
>>> 
>>> Kieran
>> 
>> I read that the some users has similar problems. Most of these users
>> violated the LwIP's threading constraints. Therefore, I created only
>> one thread which realized a simple socket-based server. Like the Unix
>> port, the tcpip thread initialized in its callback the NICs. Beside
>> these threads, my system has also an idle thread and an initd thread,
>> which creates my server example and terminates.
> 
> How does your device driver pass packets to lwIP?  There have been
> problems in the past where people have not used that interface
> correctly.
> 
>> On a real machine, the tcpip thread stucks when the socket is closed.
>> I tested my code also on qemu. By closing a socket, I got the
>> assertion "men_free: legal memory failed at line 320 in
>> lwip/src/core/mem.c".
> 
> That suggests that something is trying to free an invalid pointer.
> Again this points at state corruption.  I wonder if you have problems
> with stack overflow on your system or something like that?
> 
> Kieran
> 
> 
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