Re: PROBLEM: 3.0-rc kernels unbootable since -rc3

Paul E. McKenney
2011-07-12T20:53:05Z

On Tue, Jul 12, 2011 at 03:07:56PM -0400, Konrad Rzeszutek Wilk wrote:
> > > > Disabling CONFIG_NO_HZ would be an interesting test case.
> > >
> > > Hadn't done that yet. Compiling a kernel with "# CONFIG_NO_HZ is not set"
> > > right now.
>
> Log: http://darnok.org/xen/loop_cnt-extra-patch-no-hz-disabled.log
> config:http://darnok.org/xen/loop_cnt-extra-patch-no-hz-disabled+.config
> Patch: http://darnok.org/xen/loop_cnt-extra-patch-no-hz-disabled.patch

OK, thank you for trying this out. No joy, but to be expected given
Peter's later email.

Thanx, Paul

> > > > > > But the loop in task_waking_fair() looks like the most prominent smoking
> > > > > > gun at the moment.
> > > >
> > > > And could you also please try out the patch that I posted earlier?
> > >
> > > With the previous patch and the .. this is getting confusing. With this patch:
> > > http://darnok.org/xen/loop_cnt-extra.patch
> >
> > That is indeed the patch I intended.
>
> <nods>
> >
> > > I get this output: http://darnok.org/xen/log.loop_cnt-extra-patch (one guest
> > > with 4 VCPUS) and http://darnok.org/xen/loop_cnt-extra-patch.log (the guest with 16 VCPUs)
> >
> > OK, so the infinite loop in task_waking_fair() happens even if RCU callbacks
> > are deferred until after the scheduler is fully initialized. Sounds like
> > one for the scheduler guys. ;-)
>
> Yikes. Well, in the meantime let me check the IPI part and see if there is something
> busted that could trigger softirq to be invoked directly.
>
> And also compile the kernel with the CONFIG_RCU_PROVE_LOCKING with some extra
> git tree you pointed me to.
> >
> > Thanx, Paul