Re: Panic when cpu hot-remove

[fandongdong]

å 2015/6/18 15:27, fandongdong åé:
> å 2015/6/18 13:40, Jiang Liu åé:
> > On 2015/6/17 22:36, Alex Williamson wrote:
> > > On Wed, 2015-06-17 at 13:52 +0200, Joerg Roedeljoro wrote:
> > > > On Wed, Jun 17, 2015 at 10:42:49AM +0000, èåå wrote:
> > > > > Hi maintainer,
> > > > >
> > > > > We found a problem that a panic happen when cpu was hot-removed. 
> > > > > We also trace the problem according to the calltrace information.
> > > > > An endless loop happen because value head is not equal to value 
> > > > > tail forever in the function qi_check_fault( ).
> > > > > The location code is as follows:
> > > > >
> > > > >
> > > > > do {
> > > > >          if (qi->desc_status[head] == QI_IN_USE)
> > > > >          qi->desc_status[head] = QI_ABORT;
> > > > >          head = (head - 2 + QI_LENGTH) % QI_LENGTH;
> > > > >      } while (head != tail);
> > > > Hmm, this code interates only over every second QI descriptor, and 
> > > > tail
> > > > probably points to a descriptor that is not iterated over.
> > > >
> > > > Jiang, can you please have a look?
> > > I think that part is normal, the way we use the queue is to always
> > > submit a work operation followed by a wait operation so that we can
> > > determine the work operation is complete.  That's done via
> > > qi_submit_sync().  We have had spurious reports of the queue getting
> > > impossibly out of sync though.  I saw one that was somehow linked to 
> > > the
> > > I/O AT DMA engine.  Roland Dreier saw something similar[1]. I'm not
> > > sure if they're related to this, but maybe worth comparing. Thanks,
> > Thanks, Alex and Joerg!
> >
> > Hi Dongdong,
> >     Could you please help to give some instructions about how to
> > reproduce this issue? I will try to reproduce it if possible.
> > Thanks!
> > Gerry
> Hi Gerry,
>
> We're running kernel 4.1.0 on a 4-socket system and  we want to 
> offline socket 1.
> Steps as follows:
>
> echo 1 > /sys/firmware/acpi/hotplug/force_remove
> echo 1 > /sys/devices/LNXSYSTM:00/LNXSYBUS:00/ACPI0004:01/eject
>
> Thanks!
> Dongdong
> > > Alex
> > >
> > > [1] 
> > > http://lists.linuxfoundation.org/pipermail/iommu/2015-January/011502.html
> > >
> > > --
> > > To unsubscribe from this list: send the line "unsubscribe 
> > > linux-kernel" in
> > > the body of a message to majordomo@xxxxxxxxxxxxxxx
> > > More majordomo info at http://vger.kernel.org/majordomo-info.html
> > > Please read the FAQ at  http://www.tux.org/lkml/
> > .

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/