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

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Date:	Tue, 12 Jul 2011 13:52:58 -0700
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
Cc:	Jeremy Fitzhardinge <jeremy@...p.org>,
	xen-devel@...ts.xensource.com,
	julie Sullivan <kernelmail.jms@...il.com>,
	linux-kernel@...r.kernel.org, chengxu@...ux.vnet.ibm.com,
	peterz@...radead.org
Subject: Re: PROBLEM: 3.0-rc kernels unbootable since -rc3

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
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