Re: [Xen-devel] making xenstore domain easy configurable

[Doug Goldstein <cardoe@xxxxxxxxxx>]

On 6/28/16 11:27 AM, Jan Beulich wrote:
>>>> On 28.06.16 at 15:59, <andrew.cooper3@xxxxxxxxxx> wrote:
>> For xenstored running in the same domain as the toolstack, sockets are
>> less overhead than the shared memory ring, as no hypercalls are
>> involved.  There is also the unfortunate problem that one of the two
>> linux devices for xenstored *still* causes deadlocks when used; a
>> problem which is unresolved from Linux 3.14.
> 
> And these deadlocks aren't possibly related to the introduction
> of FMODE_ATOMIC_POS, and hence would be resolved by
> https://patchwork.kernel.org/patch/8752411/(or something along
> those lines, if nonseekable_open() isn't used on that code path)?
> I ask because we had a similar report, but when I put together the
> (refused upstream) patch I assumed the files under /dev wouldn't
> have the same issue (and I still didn't check whether they would).
> 
> Jan
> 

They are related to FMODE_ATOMIC_POS. The nodes under /dev don't
experience the same issues. Jonathan Creekmore and I submitted patches
to make /dev/xen/xenbus and /dev/xen/privcmd the preferred interfaces
used by the Xen tools over their /proc/xen/ counterparts in an attempt
to prevent people from being bitten by that. One of the patches made it
into 4.6 and the other didn't make it in until 4.7.

-- 
Doug Goldstein

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