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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: Mon, 12 Oct 2015 22:41:42 +0200
User-agent: Mutt/1.5.21 (2010-09-15)

Hi Stephen,

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.


- Do *NOT* call anything in interrupt context, nothing, never, 
absolutely never, use your OS semaphore signaling to an 
Ethernet/serial/… RX thread

- memp_*, pbuf_*, functions are thread-safe if SYS_LIGHTWEIGHT_PROT is 
set, and again, thread safe does not mean it is interrupt safe

- Do *NOT* call any function from the RAW API outside lwIP thread

- Use Netconn or Socket API in others threads, but keep in mind you 
should not share a Netconn/Socket control block between threads, (or use 
proper locking if you really have to, of course).

- Please read doc/rawapi.txt from the lwIP source which explain that 
more comprehensively


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