Re: ZFS + FreeBSD XEN dom0 panic

On Mon, Mar 21, 2022 at 05:35:15PM +0100, Roger Pau Monné wrote:
> On Mon, Mar 21, 2022 at 04:07:48PM +0200, Ze Dupsys wrote:
> > On 2022.03.21. 13:14, Roger Pau Monné wrote:
> > > I think the problem is not likely with the xenstore implementation
> > > (ie: xs_talkv) but rather a race with how the FreeBSD kernel detects
> > > and manages addition and removal of devices that hang off xenbus.
> > > 
> > > I'm afraid there's too much data below for me to parse it.
> > 
> > Understood. Sounds more tricky than i thought. What could i do to make data
> > more useful?
> 
> I have another patch for you to try. This will make the system a bit
> chatty, let's see what you get.

Forgot to mention: when testing the patch attached to the previous
email there's no need to push the system until you get a panic. Just
detecting when you have stale xbbd entries in sysctl would be enough,
or alternatively when you start to see entries in the output of
`xenstore-ls -fp` like:

/local/domain/0/backend/vbd/XX/XXXXX = ""   (n0)
/local/domain/0/backend/vbd/XX/XXXXX/feature-barrier = "1"   (n0)
/local/domain/0/backend/vbd/XX/XXXXX/feature-flush-cache = "1"   (n0)
/local/domain/0/backend/vbd/XX/XXXXX/max-ring-page-order = "5"   (n0)

Note the lack of a '/local/domain/0/backend/vbd/XX/XXXXX/state' node.

At that point I would request that you attach the output of
`xenstore-ls -fp` together with the full serial log since the system
booted.

You might not need a lot of iterations to trigger that state.

Thanks, Roger.