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

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

Hi Matt,

Can you please review the patch? or any other ideas to fix the race?

Thanks,
Joe

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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Joe Jin | Software Development Senior Manager | +8610.6106.5624
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