Re: Soft-Lockup/Race in networking in 2.6.31-rc1+195 ( possibly?caused by netem)

Jarek Poplawski
2009-07-04T06:37:17Z

On Fri, Jul 03, 2009 at 06:55:53PM -0700, David Miller wrote:
> From: Jarek Poplawski <jarkao2@gmail.com>
> Date: Sat, 4 Jul 2009 00:56:40 +0200
>
> > On Fri, Jul 03, 2009 at 01:22:20PM -0700, David Miller wrote:
> >> Well, if you look at that commit the bisect pointed to Jarek, it is a
> >> change which starts causing a situation which never happened before.
> >> Namely, timers added on one cpu can be migrated and fire on another.
> >>
> >> So this could be exposing races in the networking that technically
> >> always existed.
> >
> > I'm not sure I get your point; could you give some example?
> > Actually, I've suspected races in timers code.
>
> Let's say that a particular networking timer always gets
> re-added on the cpu where the timer fires.
>
> In that case, beforehand, no inter-cpu races could possibly
> be tested. But with the new timer code, such races could
> now be potentially triggered.

Maybe I still miss something, but even if it were possible, lockdep
should have reported such things long ago.

Jarek P.