netdev - Re: Linux 3.6.x kernel crash in tcp_slow_start / bictcp_cong

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Date:	Wed, 23 Jan 2013 23:00:39 +0100
From:	Hannes Frederic Sowa <hannes@...essinduktion.org>
To:	Pasi Kärkkäinen <pasik@....fi>
Cc:	netdev@...r.kernel.org
Subject: Re: Linux 3.6.x kernel crash in tcp_slow_start / bictcp_cong_avoid with wfica

On Wed, Jan 23, 2013 at 11:51:51PM +0200, Pasi Kärkkäinen wrote:
> On Wed, Jan 23, 2013 at 10:44:45PM +0100, Hannes Frederic Sowa wrote:
> > On Wed, Jan 23, 2013 at 06:12:38PM +0200, Pasi Kärkkäinen wrote:
> > > My laptop running Fedora 17 randomly crashes when using wfica (Citrix Receiver / ICA Client) 
> > > proprietary closed source client for accessing remote desktop server. 
> > > wfica is running as a normal user, so it shouldn't be able to cause a kernel crash. 
> > > 
> > > Crashes seem to happen most often when I use either wlan- or 3G mobile data Internet connection. 
> > > These kernel crashes happen ramdomly, often 1-2 times a week. 
> > > What usually happens is that I notice the Internet connection has died, 
> > > and when I check the kernel dmesg I'm seeing the traceback. 
> > > At this point I'm still able to use the gnome desktop for maybe 1-5 minutes, 
> > > but applications start to fail one by one, and finally everything just halts 
> > > and I need to power cycle the laptop. 
> > 
> > Would it be possible to capture a strace -e network, so we could see which
> > setsockopt combinations are being applied to the socket. Is capturing ss -ioem
> > in such moments still possible?
> > 
> 
> I don't think I'm able to strace or anything at that point.. 
> It took me at least 10 tries (=crashes) before I was able to "dmesg > log.txt" successfully .. 
> (usually writing/redirecting to a file fails because the disk/fs is already unavailable..)

The strace can be done without the system going downhill. Instead of
-e network, "-e socket,connect,setsockopt,getsockopt,shutdown,close"
can be used to reduce the output.

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