From mboxrd@z Thu Jan  1 00:00:00 1970
From: Tim Deegan <tim@xen.org>
Subject: Re: [PATCH 03 of 12] x86/mm: Add per-page locking for
	memory sharing, when audits are disabled
Date: Thu, 19 Jan 2012 13:02:30 +0000
Message-ID: <20120119130230.GI66164@ocelot.phlegethon.org>
References: <patchbomb.1326682580@xdev.gridcentric.ca>
	<11916fe20dd274ff370b.1326682583@xdev.gridcentric.ca>
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To: Andres Lagar-Cavilla <andres@lagarcavilla.org>
Cc: xen-devel@lists.xensource.com, ian.campbell@citrix.com, andres@gridcentric.ca, keir.xen@gmail.com, JBeulich@suse.com, ian.jackson@citrix.com, adin@gridcentric.ca
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At 21:56 -0500 on 15 Jan (1326664583), Andres Lagar-Cavilla wrote:
> @@ -510,26 +684,63 @@ int mem_sharing_share_pages(struct domai
>      smfn = get_gfn(sd, sgfn, &smfn_type);
>      cmfn = get_gfn(cd, cgfn, &cmfn_type);
>  
> -    ret = XEN_DOMCTL_MEM_SHARING_S_HANDLE_INVALID;
> -    spage = mem_sharing_lookup(mfn_x(smfn));
> -    if ( spage == NULL )
> +    /* This tricky business is to avoid two callers deadlocking if 
> +     * grabbing pages in opposite client/source order */

I think you need to delete the XXX comment just above. :)

Tim.