Re: [Xen-devel] [BUG] kernel BUG at drivers/block/xen-blkfront.c:1711

[Evgenii Shatokhin <eshatokhin@xxxxxxxxxxxxx>]

On 11.07.2016 13:37, George Dunlap wrote:
> On Mon, Jul 11, 2016 at 9:50 AM, Evgenii Shatokhin
> <eshatokhin@xxxxxxxxxxxxx> wrote:
> > On 06.06.2016 11:42, Dario Faggioli wrote:
> > > Just Cc-ing some Linux, block, and Xen on CentOS people...
> > Ping.
> >
> > Any suggestions how to debug this or what might cause the problem?
> >
> > Obviously, we cannot control Xen on the Amazon's servers. But perhaps there
> > is something we can do at the kernel's side, is it?
> I think part of the problem is that your report has confused people so
> that everyone cc'd thinks it's someone else's problem. :-)
>
> To wit..
>
> > > > One of our users gets kernel panics from time to time when he tries
> > > > to
> > > > use his Amazon EC2 instance with CentOS7 x64 in it [1]. Kernel panic
> > > > happens within minutes from the moment the instance starts. The
> > > > problem
> > > > does not show up every time, however.
> > > >
> > > > The user first observed the problem with a custom kernel, but it was
> > > > found later that the stock kernel 3.10.0-327.18.2.el7.x86_64 from
> > > > CentOS7 was affected as well.
> ...by mentioning the exact CentOS kernel version, but not the version
> of the "custom kernel" you used, I suspect the people familiar with
> netfront filtered this out as something to be taken care of by the
> CentOS / RHEL system.
The custom kernel is based on the same RHEL's kernel 
3.10.0-327.18.2.el7.x86_64 as the one from CentOS 7. We did not change 
Xen-related parts there.
> If you can reproduce this with a relatively recent stock kernel,
> please post the kernel version and the debug information.
>
> If you can't, then it's likely to be an issue that RH needs to take
> care of by backporting whatever change fixed the issue.
Thanks for the suggestion.

Yes, if the patch Bob Liu has proposed does not help, I will try to 
reproduce the problem on a recent mainline kernel.
The difficult part is that the problem is rather hard to reproduce, but, 
well, it is another story.
> Thanks,
>   -George
> .
Regards,
Evgenii

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