Re: rcu: INFO: rcu_preempt detected stalls on CPUs/tasks on v3.6

[John Stultz]

On 08/06/2012 10:21 AM, John Stultz wrote:
> On 08/05/2012 09:55 AM, Sasha Levin wrote:
> > On 07/30/2012 03:17 PM, Avi Kivity wrote:
> > > Possible causes:
> > >   - the APIC calibration in the guest failed, so it is programming too
> > > low values into the timer
> > >   - it actually needs 1 us wakeups and then can't keep up (esp. as kvm
> > > interrupt injection is slowing it down)
> > >
> > > You can try to find out by changing
> > > arch/x86/kvm/lapic.c:start_lapic_timer() to impose a minimum wakeup of
> > > (say) 20 microseconds which will let the guest live long enough for you
> > > to ftrace it and see what kind of timers it is programming.
> > I've kept trying to narrow it down, and found out It's triggerable 
> > using adjtimex().
Sorry, one more question: Could you provide details on how is it 
trigger-able using adjtimex?

thanks
-john

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