Re: [lwip-users] multi-threaded environment

[Leon Woestenberg]

Hello Tom,

Tom C. Barker wrote:
> Thanks Peter.
>
> I have resolved the issue of timeouts and my stack
> runs as long as I make my main loop TCPIP_THREAD_PRIO + 1
> and I don't use DHCP timers...go figure
Instead of focussing finding out when it works, you should
find out when it breaks.

Only then can we think of fixing the problem.

> I use descending priorities so TCPIP_THREAD_PRIO + 1 is 
> one higher priority than the tcp timers.
>
> Whenever I make the main loop TCPIP_THREAD_PRIO, add
> a thread for DHCP timers or add DHCP timers while I'm in
> the tcpip_init thread, I get one of the following ASSERTs.
>
>    Assertion "memp sanity" failed...memp.cpp (memp.c)
>    Assertion "pbuf_free: p->ref > 0" failed at line 576 in pbuf.cpp (pbuf.c)
Are you sure your calls into lwIP are serialized?

lwIP must be regarded as non thread safe; you must
1) serialize calling the functions
2) make sure a thread which is in an lwIP call, is not pre-empted
   by another thread which then performs an lwIP call as well.

Usually, you can do so with a (priority-inheriting) mutual exclusion 
semaphore.

Good luck,

Leon.


> -----Original Message-----
> From: address@hidden
> [mailto:address@hidden Behalf
> Of Peter Graf
> Sent: Monday, March 22, 2004 2:23 AM
> To: Mailing list for lwIP users
> Subject: Re: [lwip-users] multi-threaded environment
>
>
> Tom C. Barker wrote:
>
>
> > [Snip]
> > Additionally, has anyone written a guide to initializing
> > tasks. I've found samples but it seems that no real 
> > explanations are lying around.
>
> No, but for me reading the according portions of sys_arch.c from the 
> Unix port was not too hard, and gave me a good idea of what had to be done.
>
> As you mention task initialization (which is quite unproblematic) I'd 
> like to point to the more complicated (clean) removal of tasks from lwIP 
> usage. This issue hasn't been given much (any?) attention, probably 
> because embedded multitasking systems tend to create tasks only once and 
> then never remove them. Are there any plans to standardize task removal, 
> or is it not of general interest? (I have always been postponing to 
> implement it, but someday I'll surely need it.)
>
> Peter
>
>
>
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