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

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

On 11/20/13 00:26, Matt Wilson wrote:
> On Tue, Nov 19, 2013 at 09:06:51AM -0500, Konrad Rzeszutek Wilk wrote:
>> On Tue, Nov 19, 2013 at 06:41:37PM +0800, Joe Jin wrote:
> [...]
>>>
>>> Yes your right, this patch just reduce the window. 
>>> I created a new patch for this, please comment!
>>>
>>> [PATCH] xend: getVCPUInfo should handle died domain
>>>
>>> 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 already 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 handle the situation.
>>>
>>> Signed-off-by: Joe Jin <joe.jin@oracle.com>
>>> ---
>>>  tools/python/xen/xend/XendDomainInfo.py |    4 ++++
>>>  1 files changed, 4 insertions(+), 0 deletions(-)
>>>
>>> diff --git a/tools/python/xen/xend/XendDomainInfo.py b/tools/python/xen/xend/XendDomainInfo.py
>>> index e9d3e7e..c6414ed 100644
>>> --- a/tools/python/xen/xend/XendDomainInfo.py
>>> +++ b/tools/python/xen/xend/XendDomainInfo.py
>>> @@ -34,6 +34,7 @@ import os
>>>  import stat
>>>  import shutil
>>>  import traceback
>>> +import errno
>>>  from types import StringTypes
>>>  
>>>  import xen.lowlevel.xc
>>> @@ -1541,6 +1542,9 @@ class XendDomainInfo:
>>>              return sxpr
>>>  
>>>          except RuntimeError, exn:
>>> +            # Domain already died.
>>> +            if exn.args[0] == errno.ESRCH:
>>> +                return sxpr
>>>              raise XendError(str(exn))
>>>  
>>>  
>>
>> Adding Matt as he has stepped up to be the bug-fix maintainer of Xend
>> (I think? Is that correct - should that be reflected in the MAINTAINERS file?)
> 
> This should probably be handling xen.lowlevel.xc.Error. There's no
> guarantee that a RuntimeError will have arguments, though
> xen.lowlevel.xc.Error seems to always be constructed with arguments.
> 

Do you means when ESRCH returned to xc, generate fake vcpu info rather
than raise exception? 

I created a patch for this, can you please review?

Subject: xc: build fake vcpu info when domain already died

Signed-off-by: Joe Jin <joe.jin@oracle.com>
---
 tools/python/xen/lowlevel/xc/xc.c |   26 ++++++++++++++++++++++----
 1 files changed, 22 insertions(+), 4 deletions(-)

diff --git a/tools/python/xen/lowlevel/xc/xc.c b/tools/python/xen/lowlevel/xc/xc.c
index 2625fc4..5c40e37 100644
--- a/tools/python/xen/lowlevel/xc/xc.c
+++ b/tools/python/xen/lowlevel/xc/xc.c
@@ -384,6 +384,7 @@ static PyObject *pyxc_vcpu_getinfo(XcObject *self,
     int rc, i;
     xc_cpumap_t cpumap;
     int nr_cpus;
+    int died = 0;
 
     static char *kwd_list[] = { "domid", "vcpu", NULL };
     
@@ -396,8 +397,13 @@ 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)
+            died = 1;
+        else
+            return pyxc_error_to_exception(self->xc_handle);
+    }
 
     cpumap = xc_cpumap_alloc(self->xc_handle);
     if(cpumap == NULL)
@@ -406,8 +412,20 @@ static PyObject *pyxc_vcpu_getinfo(XcObject *self,
     rc = xc_vcpu_getaffinity(self->xc_handle, dom, vcpu, cpumap);
     if ( rc < 0 )
     {
-        free(cpumap);
-        return pyxc_error_to_exception(self->xc_handle);
+        if (errno == ESRCH)
+            died = 1;
+        else
+        {
+            free(cpumap);
+            return pyxc_error_to_exception(self->xc_handle);
+        }
+    }
+
+    if (died)
+    {
+        memset(&info, 0, sizeof(info));
+        info.cpu_time = 0.0;
+        info.cpu = -1;
     }
 
     info_dict = Py_BuildValue("{s:i,s:i,s:i,s:L,s:i}",
-- 
1.7.1