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Re: [Xen-devel] BUG: unable to handle kernel NULL pointer dereference - xen_spin_lock_flags

1On Tue, 2012-02-14 at 00:54 +0000, Christopher S. Aker wrote:
> On Feb 13, 2012, at 5:41 PM, Christopher S. Aker wrote:
> > Network stress testing (iperf, UDP, bidirectional) the above stack reliably 
> > BUGs on both 3.0.4 and 3.2.5, and on both IGB or e1000e NICs with the 
> > following:
> > 
> > BUG: unable to handle kernel NULL pointer dereference at 00000474
> > IP: [<c100e967>] xen_spin_lock_flags+0x27/0x70
> This happens regardless of CONFIG_PARAVIRT_SPINLOCKS enabled or disabled.

I think that rules out the recent pv spinlock bug (fixed by
7a7546b377bdaa25ac77f33d9433c59f259b9688, in various stable trees

What line of code does that IP correspond to within xen_spin_lock_flags?
Likewise the one in xen_netbk_schedule_xenvif from the stack.

I suspect this must be &netbk->net_schedule_list_lock but I don't see
how that can ever be NULL nor does the offset appear to be 0x474, at
least in my tree -- although that may depend on debug options.

Are you rebooting guests or plug/unplugging vifs while this is going on?
What about hotplugging CPUs (dom0 in particular)?

Does this happen as soon as the test starts or does it work for a bit
before failing?


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