Re: Strange crash on Dell R720xd

[Laurent CARON <lcaron@unix-scripts.info>]

On Tue, Oct 16, 2012 at 02:48:25PM +0200, Borislav Petkov wrote:
> On Tue, Oct 16, 2012 at 11:26:01AM +0200, Laurent CARON wrote:
> > On Tue, Oct 16, 2012 at 11:03:53AM +0200, Borislav Petkov wrote:
> > > That's:
> > > 
> > >                 BUG_ON(async_tx_test_ack(depend_tx) || txd_next(depend_tx) ||
> > > 			txd_parent(tx));
> > > 
> > > but probably the b0rkage happens up the stack. And this __raid_run_ops
> > > is probably starting the whole TX so maybe we should add
> > > linux-raid@vger.kernel.org to CC. Added.
> > 
> > 
> > Hi,
> > 
> > The machines seem stable after disabling I/O AT DMA at the BIOS level.
> 
> That's a good point because the backtrace goes through I/O AT DMA so it
> could very well be the culprit. Let's add some more people to Cc.
> 
> Vinod/Dan, here's the BUG_ON Laurent is hitting:
> 
> http://marc.info/?l=linux-kernel&m=135033064724794&w=2
> 
> and it has ioat2_tx_submit_unlock in the backtrace. Disabling ioat dma
> in the BIOS makes the issue disappear so ...
> 
> > > What is that "r510" thing in the kernel version? You have your patches
> > > ontop? If yes, please try reproducing this with a kernel.org kernel
> > > without anything else ontop.
> > 
> > My kernel is vanilla from Kernel.org. The -r510 string is because I
> > tried it on a -r510 also.
> 
> Ok, good.
> 
> > > Also, it might be worth trying plain 3.6 to rule out a regression
> > > introduced in the stable 3.6 series.
> > 
> > I tried 3.5.x, 3.6, 3.6.1, 3.6.2 with exactly the same results.
> > 
> > For now, I did create more volumes, rsync lors of data over the network
> > to the disks with no crashs (after disabling I/O AT DMA).
> 
> And when you do this with ioat dma enabled, you get the bug, right? So
> it is reproducible...?

It is 100% reproductible. The only "nondeterministic" point is the time
it takes to have the machine crash.