linux-kernel - Re: [bug] stuck localhost TCP connections, v2.6.26-rc3+

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Date:	Fri, 30 May 2008 20:18:39 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Ilpo J?rvinen <ilpo.jarvinen@...sinki.fi>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Netdev <netdev@...r.kernel.org>,
	"David S. Miller" <davem@...emloft.net>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [bug] stuck localhost TCP connections, v2.6.26-rc3+

* Ingo Molnar <mingo@...e.hu> wrote:

> after about 50 bootups i got a hung test again:
> 
> titan:~/tip> netstat -nt
> Active Internet connections (w/o servers)
> Proto Recv-Q Send-Q Local Address               Foreign Address             
> State
> tcp        0      0 10.0.1.14:22                10.0.1.16:58062  ESTABLISHED
> tcp        0      0 10.0.1.14:22                10.0.1.16:60109  ESTABLISHED
> tcp        0  86368 10.0.1.14:43914             10.0.1.16:3632   ESTABLISHED
> 
> and this time with CUBIC_TCP disabled - so that was a red herring.

ah, in retrospect i realized that this test had one flaw: some of the 
systems i the build cluster already ran a newer kernel and hence were 
targets for this bug.

so i turned off CONFIG_TCP_CONG_CUBIC on all the testboxes and rebooted 
the cluster boxes into 2.6.25, and the hung sockets are now gone. (about 
150 successful iterations)

i did another change as well: i removed the localhost distcc component. 
I'll reinstate that now to make sure it's really related to 
TCP_CONG_CUBIC and not to localhost networking.

	Ingo
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