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Re: [Xen-devel] Question on grant copying a previous grant mapped page

On Wed, 2012-02-29 at 10:39 +0000, Paul Durrant wrote:
> That sounds like a basic bug in gnttab2 and it also sounds very similar to 
> something I thought I already fixed.
>   Paul

You mean this one?

changeset:   22994:299ed79acecf
user:        Keir Fraser <keir@xxxxxxx>
date:        Tue Mar 08 16:30:30 2011 +0000
files:       xen/common/grant_table.c xen/include/xen/grant_table.h
Fix rcu domain locking for transitive grants

When acquiring a transitive grant for copy then the owning domain
needs to be locked down as well as the granting domain. This was being
done, but the unlocking was not. The acquire code now stores the
struct domain * of the owning domain (rather than the domid) in the
active entry in the granting domain. The release code then does the
unlock on the owning domain.  Note that I believe I also fixed a bug
where, for non-transitive grants the active entry contained a
reference to the acquiring domain rather than the granting
domain. From my reading of the code this would stop the release code
for transitive grants from terminating its recursion correctly.

Signed-off-by: Paul Durrant <paul.durrant@xxxxxxxxxx>

This is the non-transitive case, but active entry contains no reference
to any domain.


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