Xen devel - Feb 2007 - [PATCH] [XEN][ACM] fix missing spin_unlock

Insert a missing spin_unlock statement.

Signed-off-by: Stefan Berger <stefanb@us.ibm.com>

Keir,

  I have a question regarding the event channel data structure. It looks
like a stale entry is in the event channel array indicating that a event
channel at a given port has a certain remote domain as target. However,
that domain does not exist anymore and therefore the code section where
I add the spin_unlock() call gets triggered now. Could this be a bug in
the domain-cleanup code?

  I can trigger this problem when running the xm-test suite with ACM
compiled into Xen. After 159 domains have been created, which happens to
be during the list tests, the stale port entry shows up and remains. The
list tests when run after a reboot do not trigger this, though.

  Stefan



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On 26/2/07 19:57, "Stefan Berger" <stefanb@us.ibm.com> wrote:
>  I have a question regarding the event channel data structure. It looks
> like a stale entry is in the event channel array indicating that a event
> channel at a given port has a certain remote domain as target. However,
> that domain does not exist anymore and therefore the code section where
> I add the spin_unlock() call gets triggered now. Could this be a bug in
> the domain-cleanup code?
> 
>   I can trigger this problem when running the xm-test suite with ACM
> compiled into Xen. After 159 domains have been created, which happens to
> be during the list tests, the stale port entry shows up and remains. The
> list tests when run after a reboot do not trigger this, though.
When one end of a fully-bound interdomain event channel is closed, the
remote port enters state ECS_UNBOUND. At this point it still refers to the
remote domain by domid, even if the remote domain subsequently dies. In fact
this is exactly the state that all currently-interdomain-bound remote ports
will immediately enter when a domain is destroyed. It''s safe and
expected.
Since an ACM check will happen when moving from state ECS_UNBOUND to
ECS_INTERDOMAIN you get the chance to check credentials are okay and hence
deal with the case that the domid gets reused by a domain who should not be
allowed to communicate to the ECS_UNBOUND port.

 -- Keir



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