[Qemu-devel] [PATCH v7 04/11] qemu.py: use poll() instead of 'returncode'

[Amador Pahim]

The 'returncode' Popen attribute is not guaranteed to be updated. It
actually depends on a call to either poll(), wait() or communicate().

On the other hand, poll() will: "Check if child process has terminated.
Set and return returncode attribute."

Let's use the poll() to check whether the process is running and also
to get the updated process exit code, when the process is finished.

As consequence, the shutdown() calls to self._load_io_log()
self._post_shutdown() are now always executed to make sure we cleanup
even if VM is not running when the shutdown() is called.

Signed-off-by: Amador Pahim <address@hidden>
---
 scripts/qemu.py | 19 +++++++++++++------
 1 file changed, 13 insertions(+), 6 deletions(-)

diff --git a/scripts/qemu.py b/scripts/qemu.py
index 51545f7f97..774f971f69 100644
--- a/scripts/qemu.py
+++ b/scripts/qemu.py
@@ -98,12 +98,12 @@ class QEMUMachine(object):
             raise
 
     def is_running(self):
-        return self._popen is not None and self._popen.returncode is None
+        return self._popen is not None and self._popen.poll() is None
 
     def exitcode(self):
         if self._popen is None:
             return None
-        return self._popen.returncode
+        return self._popen.poll()
 
     def get_pid(self):
         if not self.is_running():
@@ -111,8 +111,15 @@ class QEMUMachine(object):
         return self._popen.pid
 
     def _load_io_log(self):
-        with open(self._qemu_log_path, "r") as fh:
-            self._iolog = fh.read()
+        '''
+        Load the Qemu log file content (if available) into the proper
+        instance variable
+        '''
+        try:
+            with open(self._qemu_log_path, "r") as fh:
+                self._iolog = fh.read()
+        except IOError:
+            pass
 
     def _base_args(self):
         if isinstance(self._monitor_address, tuple):
@@ -168,8 +175,8 @@ class QEMUMachine(object):
             if exitcode < 0:
                 LOG.debug('qemu received signal %i: %s', -exitcode,
                           ' '.join(self._args))
-            self._load_io_log()
-            self._post_shutdown()
+        self._load_io_log()
+        self._post_shutdown()
 
     underscore_to_dash = string.maketrans('_', '-')
     def qmp(self, cmd, conv_keys=True, **args):
-- 
2.13.5