Re: [Xen-devel] [PATCH] xend: do not polling vcpus info if guest state is not RUNNING or PAUSED

[Dario Faggioli <dario.faggioli@xxxxxxxxxx>]

On mar, 2013-11-19 at 14:13 +0800, Joe Jin wrote:
> When created new guest on NUMA server, xend tried to get the best node by
> calculated all vcpus info, the race is if other geust is rebooting, the
> guest in the list when entered find_relaxed_node(), but when call
> getVCPUInfo() the guest be terminated, then getVCPUInfo() will fail with
> below error:
> 
> [2013-09-04 20:01:26 6254] ERROR (XendDomainInfo:496) VM start failed
> Traceback (most recent call last):
>   File "/usr/lib64/python2.4/site-packages/xen/xend/XendDomainInfo.py", line 
> 482, in start
>     XendTask.log_progress(31, 60, self._initDomain)
>   File "/usr/lib64/python2.4/site-packages/xen/xend/XendTask.py", line 209, 
> in log_progress
>     retval = func(*args, **kwds)
>   File "/usr/lib64/python2.4/site-packages/xen/xend/XendDomainInfo.py", line 
> 2918, in _initDomain
>     node = self._setCPUAffinity()
>   File "/usr/lib64/python2.4/site-packages/xen/xend/XendDomainInfo.py", line 
> 2835, in _setCPUAffinity
>     best_node = find_relaxed_node(candidate_node_list)[0]
>   File "/usr/lib64/python2.4/site-packages/xen/xend/XendDomainInfo.py", line 
> 2803, in find_relaxed_node
>     cpuinfo = dom.getVCPUInfo()
>   File "/usr/lib64/python2.4/site-packages/xen/xend/XendDomainInfo.py", line 
> 1600, in getVCPUInfo
>     raise XendError(str(exn))
> XendError: (3, 'No such process')
> 
> This patch will let find_relaxed_node() only polling the RUNNING or PAUSED
> guest vpus info to avoid the race.
> 
> Signed-off-by: Joe Jin <joe.jin@xxxxxxxxxx>
>
The idea looks ok. Unfortunately, I know nothing of xend, thus I really
don't feel comfortable enough to provide a formal Ack.

Basically, I don't know whether this patch is the best way to fix the
issue, if there are other ways, etc, but the problem certainly exist and
the solution sounds sound. :-)

Dario

-- 
<<This happens because I choose it to happen!>> (Raistlin Majere)
-----------------------------------------------------------------
Dario Faggioli, Ph.D, http://about.me/dario.faggioli
Senior Software Engineer, Citrix Systems R&D Ltd., Cambridge (UK)

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