[Xen-devel] [patch] new version of find_domain_by_id() without reference count [0/6]

["Santos, Jose Renato G" <joserenato.santos@xxxxxx>]

Following Keir suggestion, this is set of patches to add a new version
of find_domain_by_id() which does not increment the domain reference
counter. This reduces the overhead and can be used by any function which
does not need to keep a domain reference beyond its current invocation,
as the rcu mechanism prevents the domain from being removed under our
feet. Of course, this can only be applied after the RCU patch posted
earlier.

Beyond adding the function the patch also replaces most invocations to
find_domain_by_id() with the new function find_domain_by_id_noref().
Only a few places needed to continue using the old function as the
reference was kept beyond the function invocation.
  
I only did minor tests on x86-32. Xen and dom0 boots fine and I can
create and destroy domains. But, no more exaustive tests were done. I
carefully checked if I removed all put_domain() associated with each
modified invocation of find_domain_by_id but mistakes are always
possible. It would be good to put this to some more exhaustive tests
before pushing it to the main tree. Waiting for post 3.0.4 release is
strongly suggested.

I also decomposed the patch in multiple parts so that the mantainers of
each architecture can review changes in their subtree, test  and apply
them at their convenience.

There are a total of 6 patches

1/6: add new function find_domain_by_id_noref()
2/6: replace find_domain_by_id on acm subtree
3/6: replace find_domain_by_id on common subtree
4/6: replace find_domain_by_id on arch/x86
5/6: replace find_domain_by_id on arch/powerpc
6/6: replace find_domain_by_id on arch/ia64

Regards

Renato



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