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

Konrad Rzeszutek Wilk
2011-07-12T18:02:13Z

> > http://darnok.org/xen/loop_cnt.log
> >
> > which seems to imply that we are indeed stuck in that loop
> > forever.
>
> It does indeed, thank you! Also it looks like interrupts are
> disabled, and that timekeeping is similarly out of action.

.. With the latest patch the time looks to be advancing.

> 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.
>
> > > o Problems due to portions of the code attempting to use
> > > RCU read-side critical sections while in dyntick-idle mode.
> > > Frederic Weisbecker has located some of these, (though not yet
> > > in Xen) and he has some diagnositics which may be found at:
> > >
> > > git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-2.6-rcu.git
> > >
> > > on branch eqscheck.2011.07.08a.
> > >
> > > You need to enable CONFIG_PROVE_RCU for these diagnostics to
> > > be executed.
> >
> > Ok, let me try those too.
>
> Thank you!

Will shortly do this.
>
> > > o As always, there might be bugs in RCU. ;-)
> > >
> > > 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

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)