RE: [Xen-devel] Zombie domains

["Ian Pratt" <m+Ian.Pratt@xxxxxxxxxxxx>]

> I'm using the grant table to map a shared frame between two domains.
> Domain 1 shares the frame, and Domain 2 maps it into it's address
space.
> I then make sure Domain 2 unmaps the frame, and releases all event
> channels, etc... before shutting down.  Domain 2 always remains as a
> zombie though when I do xm list.  If I dump the domain info in the Xen
> console, I get this information for the zombie domain:
> 
> (XEN) General information for domain 12:
> (XEN)     flags=6 refcnt=1 nr_pages=0 xenheap_pages=0 dirty_cpus={}
> (XEN)     handle=f4a55907-26db-d7c3-f6a7-392637013289
> (XEN) Rangesets belonging to domain 12:
> (XEN)     Interrupts { }
> (XEN)     I/O Memory { }
> (XEN)     I/O Ports  { }
> (XEN) Memory pages belonging to domain 12:
> (XEN) VCPU information and callbacks for domain 12:
> (XEN)     VCPU0: CPU0 [has=F] flags=10 upcall_pend = 01, upcall_mask =
> 00 dirty}(XEN)     Notifying guest (virq 1, port 0, stat 0/0/-1)

The usual region for zombie domains is other domains having its memory
mapped, but not in this case: nr_pages=0

> Unfortunately, these fields do not mean very much to me.  What does
> upcall_pend mean?  

There's an event pending for the domain. Not a big deal.

> Sometimes this field is 01, sometimes it's 00.  What
> about refcnt?  

Something has a reference to the domain structure, hence preventing it
from being freed. This must be a xen bug. Your OS is likely provoking an
error path that is missing a 'put'.   

Have you tried this with latest -unstable?

Ian

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