[Xen-devel] Re: [PATCH] mem_sharing: fix race condition of nominate and unshare

[Tim Deegan <Tim.Deegan@xxxxxxxxxx>]

Hi, 

At 10:03 +0000 on 12 Jan (1294826637), Jui-Hao Chiang wrote:
> After a discussion with tinnycloud, his test is working after applying
> the previous patch
> http://lists.xensource.com/archives/html/xen-devel/2010-12/txteWc7Bs5Yap.txt
> (set_shared_p2m_entry is not executed since it is in ASSERT).

Great!

> And after a few code tracing and testing, my own worry about the
> deadlock between p2m_lock and shr_lock actually disappears as the
> above discussion. So here I re-attach the patch again which includes
> another fix to recover type count when nominate fails on a page (from
> our previous dicussions).

The locking parts of this patch are already applied to the staging tree,
thanks.

The "recover type count" I still think is wrong.  The page-sharing code
can't rely on the type of a page with typecount 0.  Also in this patch
you're changing the code of the core __put_page_type() function, rather
than the page-sharing code.

Can you try the attached patch instead?  If it fixes your problem I'll
apply it. 

Cheers,

Tim.

-- 
Tim Deegan <Tim.Deegan@xxxxxxxxxx>
Principal Software Engineer, Xen Platform Team
Citrix Systems UK Ltd.  (Company #02937203, SL9 0BG)

pgt.patch
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