Re: [PATCH] xend: make xc.vcpu_getinfo() return None if guest not existed

[Joe Jin <joe.jin@oracle.com>]

Hi Matt,

Thanks for your clarification, I send an other patch to you for review,
can you please check and advice?

Thanks,
Joe

12/09/13 07:52, Matt Wilson wrote:
> On Tue, Dec 03, 2013 at 06:38:10PM +0800, Joe Jin wrote:
>> Hi Matt,
>>
>> Can you please review the patch? or any other ideas to fix the race?
> 
> Hi Joe,
> 
> I'm sorry about the delay. As you can imagine, it's a busy time of
> year for us at work.
> 
> When I commented on the original patch, I was talking about the type
> of exception you were catching. I prefer the approach in the original
> patch to this one, with one change:
> 
> The RuntimeError class isn't guaranteed to have exception arguments
> that include an errno value. The xen.lowlevel.xc.Error class is always
> set via PyErr_SetFromErrno(). So instead of
> 
>     except RuntimeError, exn:
> 
> I'd rather see:
> 
>     except xen.lowlevel.xc.Error, exn:
> 
> You can import xen.lowlevel.xc.Error to the local namespace by adding
> something like:
> 
> from xen.lowlevel.xc import xc, Error as XenError
> ...
> except XenError, exn:
> 
> Does that make sense?
> 
> --msw
> 
>> On 11/21/13 11:12, Joe Jin wrote:
>>> We hit failure when when reboot some guests at the same time,
>>> xend.log has below:
>>> [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 caused by one or more guests be rebooted between the call of
>>> find_relaxed_node()->list('all') and getVCPUInfo(). This patch will let
>>> xc.vcpu_getinfo() return None if guest not existed to avoid the failure.
>>>
>>> Signed-off-by: Joe Jin <joe.jin@oracle.com>
>>> Cc: Matt Wilson <msw@amazon.com>
>>> Cc: Keir Fraser <keir@xen.org>
>>> Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
>>> Cc: Ian Jackson <ian.jackson@eu.citrix.com>
>>> Cc: Ian Campbell <ian.campbell@citrix.com>
>>> Cc: Roger Pau Monne <roger.pau@citrix.com>
>>> ---
>>>  tools/python/xen/lowlevel/xc/xc.c       |   15 ++++++++++++---
>>>  tools/python/xen/xend/XendDomainInfo.py |    2 +-
>>>  2 files changed, 13 insertions(+), 4 deletions(-)
>>>
>>> diff --git a/tools/python/xen/lowlevel/xc/xc.c b/tools/python/xen/lowlevel/xc/xc.c
>>> index 2625fc4..9a7e589 100644
>>> --- a/tools/python/xen/lowlevel/xc/xc.c
>>> +++ b/tools/python/xen/lowlevel/xc/xc.c
>>> @@ -396,8 +396,13 @@ static PyObject *pyxc_vcpu_getinfo(XcObject *self,
>>>          return pyxc_error_to_exception(self->xc_handle);
>>>  
>>>      rc = xc_vcpu_getinfo(self->xc_handle, dom, vcpu, &info);
>>> -    if ( rc < 0 )
>>> -        return pyxc_error_to_exception(self->xc_handle);
>>> +    if ( rc < 0)
>>> +    {
>>> +        if (errno == ESRCH)
>>> +            return Py_BuildValue("");
>>> +        else
>>> +            return pyxc_error_to_exception(self->xc_handle);
>>> +    }
>>>  
>>>      cpumap = xc_cpumap_alloc(self->xc_handle);
>>>      if(cpumap == NULL)
>>> @@ -407,7 +412,11 @@ static PyObject *pyxc_vcpu_getinfo(XcObject *self,
>>>      if ( rc < 0 )
>>>      {
>>>          free(cpumap);
>>> -        return pyxc_error_to_exception(self->xc_handle);
>>> +
>>> +        if (errno == ESRCH)
>>> +            return Py_BuildValue("");
>>> +        else
>>> +            return pyxc_error_to_exception(self->xc_handle);
>>>      }
>>>  
>>>      info_dict = Py_BuildValue("{s:i,s:i,s:i,s:L,s:i}",
>>> diff --git a/tools/python/xen/xend/XendDomainInfo.py b/tools/python/xen/xend/XendDomainInfo.py
>>> index e9d3e7e..6b5fd83 100644
>>> --- a/tools/python/xen/xend/XendDomainInfo.py
>>> +++ b/tools/python/xen/xend/XendDomainInfo.py
>>> @@ -1518,7 +1518,7 @@ class XendDomainInfo:
>>>              for i in range(0, self.info['VCPUs_max']):
>>>                  if self.domid is not None:
>>>                      info = xc.vcpu_getinfo(self.domid, i)
>>> -
>>> +                    if info == None: continue
>>>                      sxpr.append(['vcpu',
>>>                                   ['number',   i],
>>>                                   ['online',   info['online']],
>>>
>>
>>


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