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Re: [lwip-devel] deadlock on high Load with loopback

From: Simon Goldschmidt
Subject: Re: [lwip-devel] deadlock on high Load with loopback
Date: Wed, 12 May 2010 16:23:54 +0200

I guess a sanity check that TCPIP_MBOX_SIZE is bigger than

Fabian Koch wrote:
> Hey all,
> I ran into the following scenario:
> 1) have loopback communication running
> 2) produce very high load (i.e. flooding) from the outside
> results in:
> - The ethernet driver running in interrupt context sends a new TCP
> IP_MSG_INPKT to the mbox which is then full.
> - The loopback also wants to output a packet and calls tcpip_callback() 
> which blocks on sending it's message to the mbox. 
> This creates a deadlock since the tcpip_thread is waiting for the mbox to 
> be free again but it won't since that same thread is responsible for 
> fetching from the mbox.
> I can fix the behavior by having MEMP_NUM_TCPIP_MSG_INPKT be smaller than 
> TCPIP_MBOX_SIZE. Then tcpip_input() fails before being able to fill up the
> mbox.
> Still it does feel like a design flaw.
> Did I do something wrong? Should we include this in the sanity checks on 
> compile? Should the behavior be redesigned?
> kind regards,
> Fabian

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