Re: [PATCH v2] xentop: add support for qdisks

["Charles Arnold" <carnold@suse.com>]

>>> On 3/19/2015 at 12:09 PM, Anthony PERARD <anthony.perard@citrix.com> wrote: 
> On Wed, Mar 18, 2015 at 04:12:26PM +0000, Ian Campbell wrote:
>> My second concern here is with the use of /var/run/xen/qmp-libxl-%i from
>> outside of libxl. I can't remember if qemu is safe against multiple
>> users of the socket. ISTR asking Anthony this before, but I don't recall
>> the answer, sorry :-(
> 
> Last time I checked, only one client at a time can connect to the socket.
> If a second user want to connect to the socket, it will be blocked until
> the first one disconnect.

This seems correct based on some of my testing.  In rare cases (perhaps not so
rare for VMs under heavy I/O load), reading the socket to get the stats times out
and so xentop will report '0' for the read/write stats until the next read attempt
that succeeds.

It looks as if we do need a second socket to qemu.  I will include that in the next
patch version.

- Charles