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

Ilpo Järvinen
2008-05-31T11:46:37Z

On Sat, 31 May 2008, Ingo Molnar wrote:

> * Ingo Molnar <mingo@elte.hu> wrote:
>
> > 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.
>
> ok, once i added back the localhost distcc component and the hung kernel
> build + stuck TCP socket bug happened again overnight:
>
> Active Internet connections (w/o servers)
> Proto Recv-Q Send-Q Local Address Foreign Address State
> tcp 72187 0 10.0.1.14:3632 10.0.1.14:47910 ESTABLISHED
> tcp 0 174464 10.0.1.14:47910 10.0.1.14:3632 ESTABLISHED
>
> so it seems distcc over localhost was the aspect that made it fail.
>
> _Perhaps_ what matters is to have the new post-rc3 TCP code on _both_
> sides of the connection. But that is just a theory - it could be timing,
> etc.

Btw, does your distcc perhaps happen enable TCP_DEFER_ACCEPT (there were
some post 2.6.25 changes into it)?

--
i.