Re: ZFS + FreeBSD XEN dom0 panic

On Mon, Mar 21, 2022 at 06:56:05PM +0100, Roger Pau Monné wrote:
> 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.

Hello,

Sorry to pester, but do you have any update on this?

I'm quite sure there are races with xenbus device attach/detach, and
the earlier we can get this sorted out the better.

Thanks, Roger.