Re: [Xen-devel] [PATCH 17/29] libxl: cancellation: Provide public ao cancellation API

[Ian Campbell <ian.campbell@xxxxxxxxxx>]

On Tue, 2015-02-10 at 20:10 +0000, Ian Jackson wrote:
> +    /*
> +     * For nested aos:
> +     *  Semantically, cancellation affects the whole tree of aos,
> +     *    not just the parent.
> +     *  libxl__ao_cancellable.ao refers to the child, so
> +     *    that the child callback sees the right ao.  (After all,
> +     *    it was code dealing with the child that set .ao.)
> +     *  But, the cancellable is recorded on the "cancellables" list
> +     *    for the ultimate root ao, so that every possible child
> +     *    cancellation occurs as a result of the cancellation of the
> +     *    parent.
> +     *  We set ao->cancelling only in the root.
> +     */

WRT this, given a tree of ao's, which ones need to be cancellable for a
cancellation to succeed? I would assume all of them do, or else the
cancellation can only occur if/when the non-cancellable ones happen to
end?

Do we(/are we going to) take steps to stop new non-cancellable ao's to
the tree once the root is cancelled?

Ian.


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