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Date: Wed, 23 Aug 2006 22:26:48 +0400
From: Oleg Bulyzhin <oleg@FreeBSD.org>
To: Gleb Smirnoff <glebius@FreeBSD.org>
Message-ID: <20060823182648.GA22888@lath.rinet.ru>
References: <20060823161649.GE76666@cell.sick.ru>
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Cc: brad@openbsd.org, David Christensen <davidch@broadcom.com>, net@FreeBSD.org
Subject: Re: bge(4) one packet wedge
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On Wed, Aug 23, 2006 at 08:16:49PM +0400, Gleb Smirnoff wrote:
>   Colleagues,
> 
>   I've faced a problem in bge(4) when a single packet is in the RX
> ring, but it isn't noticed by the driver. A reception of a packet
> triggers interrupt and both packets are processed - an old one
> and the new one.
> 
>   To reproduce the problem you need to run netperf (from ports
> collection): netserver on another host (10.0.0.1) and netperf on
> the host, where tested bge(4) is installed - 10.0.0.2. No traffic
> except netperf's should flow through this NIC, or the problem won't
> be reproduced!
> 
>   So, I run netperf client and simultaneously tcpdump on the
> another host. After few seconds there is a wedge. The last packet
> seen on 10.0.0.1 is the packet sent by 10.0.0.1 to 10.0.0.2. However
> it isn't seen on 10.0.0.2.
> 
> Ok, let's look at the receive ring:
> 
> (kgdb) p $sc->bge_rx_saved_considx
> $14 = 51
> (kgdb) p $sc->bge_ldata.bge_status_block->bge_idx[0].bge_rx_prod_idx
> $15 = 51
> 
> Looks like there is nothing to process.
> 
> However, if I run 'ping -c 1 10.0.0.2' I will get an interrupt and read
> two packets: first the old packet, and then recently sent ping.
> 
> -- 
> Totus tuus, Glebius.
> GLEBIUS-RIPN GLEB-RIPE

What happens if you trigger other interrupt (like unplug/plug cable)?
Will you get that packet?

-- 
Oleg.