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Re: [lwip-users] Problem with tcp_fasttmr

From: Simon Goldschmidt
Subject: Re: [lwip-users] Problem with tcp_fasttmr
Date: Wed, 05 Dec 2012 07:23:24 +0100

"Carr, Anthony" wrote:
> I have an application based upon lwIP v1.3.1 without an RTOS
> [..]
> I have traced the cause of the lock-up as an infinite loop in tcp_fasttmr
> where pcb and pcb->next are the same location.
> [..]
> I have looked through the archives and seen that other people have had the
> same problem but following the threads no-one offers any solution or
> explanation as to why this is happening.

Then I can only suggest you haven't looked hard enough. This is a common bug in 
lwIP ports that do not obey lwIP's threading requirements. The reason for 
pcb->next pointing to pcb is most often that more than one execution context 
calls lwIP functions at the same time. In your case (no OS), I guess you are 
using lwIP from the main loop and from an ISR (e.g. feeding packets into 
ethernet_input or ip_input from interrupt level or calling lwIP timer functions 
from interrupt level), which is not supported.


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