Re: [Xen-devel] [PATCH 01/27] tools/libxl: Fix libxl__ev_child_inuse() check for not-yet-initialised children

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 16/06/15 14:21, Ian Campbell wrote:
> On Mon, 2015-06-15 at 14:44 +0100, Andrew Cooper wrote:
>> Shortly, libxl will be juggling multiple parallel operations, and will
>> possibly have to take error decisions before some tasks have been set up.
> It would be preferable, I think, to arrange to call libxl__ev_child_init
> on all such libxl__ev_child structs either up front or certainly before
> there is any possibility of needing to unwind them.
>
> Such an init would at worst correspond to exactly the place where the
> zeroed structure you refer to is zeroed.

It is possible that one bit fails before it can be calculated whether
the second bit needs to start or not.

At the moment, all bits in libxl in this area do initialisation
immediately before use; most bits are even initialised in the function
which starts their actions.  Some bits are initialised differently
depending on the path taken to get to the initialisation site. 

It would be non-trivial to initialise everything appropriately at the
very start.

~Andrew

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