Re: [Xen-devel] linux-3.4 broken on chardonnay and huxelrebe (Re: [linux-3.4 test] 61301: regressions - FAIL)

[Ian Campbell <ian.campbell@xxxxxxxxxx>]

On Tue, 2015-09-15 at 09:47 +0100, Ian Campbell wrote:
> On Thu, 2015-09-10 at 10:32 +0100, Ian Campbell wrote:
> > The Chardonnay case suggests that either something has been backported
> > into
> > 3.4.x which has broken things (current real flights, which reliably
> > fail,
> > are running on 3.4.108) or that it is simply unreliable (or both). I
> > think
> > I need to repeat things a few times to confirm.
> 
> It turns out it was unreliable and these results were misleading. I setup
> an adhoc job which simply installed Xen and rebooted 5 times and 3.4.x
> (for
> x in increments of 10) failed reliably. In fact the fix wasn't until v3.7
> -rc1 and some adhoc runs have fingered 65fe1f0f66a5 "ahci: implement
> aggressive SATA device sleep support"[0]. I'm running a few more tests to
> confirm but this looks reasonably certain.

The tests confirmed this diagnosis.

> That commit is a new feature, so it really shouldn't have the affect of
> fixing bugs! I suspect this is something like a dodgy BIOS enabling the
> h/w
> extension, which breaks until the kernel became aware of it and either
> disables or explicitly copes with it being there.
> 
> Once the confirmation tests have run I will lock the machine and have a
> poke around and see what I can see.
> 
> I could then take it to the Linux AHCI maintainer but I suspect that a
> backport is only a slim possibility, as is someone taking the time to
> determine which bit of this feature happened to fix these systems.
> 
> IOW I'm thinking that we should apply a minimum kernel version to
> chardonnay as well as huxelrebe (once that feature exists).

I'm looking into this now.

I'm currently dithering on whether it is worth taking this to upstream
stable or not.


> 
> Ian.
> 
> [0] git.kernel.org/torvalds/c/65fe1f0f66a57380229a4ced844188103135f37b
> 

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