Re: [Qemu-devel] [PATCH v6 4/7] qemu.py: improve message on negative exit code

[Markus Armbruster]

Amador Pahim <address@hidden> writes:

> On Tue, Aug 15, 2017 at 10:26 AM, Markus Armbruster <address@hidden> wrote:
>> Amador Pahim <address@hidden> writes:
>>
>>> The current message shows 'self._args', which contains only part of the
>>> options used in the qemu command line.
>>>
>>> This patch makes the qemu full args list an instance variable and then
>>> uses it in the negative exit code message.
>>>
>>> Signed-off-by: Amador Pahim <address@hidden>
>>> ---
>>>  scripts/qemu.py | 17 ++++++++++++-----
>>>  1 file changed, 12 insertions(+), 5 deletions(-)
>>>
>>> diff --git a/scripts/qemu.py b/scripts/qemu.py
>>> index e3ea534ec4..9434ccc30b 100644
>>> --- a/scripts/qemu.py
>>> +++ b/scripts/qemu.py
>>> @@ -48,6 +48,7 @@ class QEMUMachine(object):
>>>          self._iolog = None
>>>          self._socket_scm_helper = socket_scm_helper
>>>          self._debug = debug
>>> +        self._qemu_full_args = None
>>>
>>>      # This can be used to add an unused monitor instance.
>>>      def add_monitor_telnet(self, ip, port):
>>> @@ -140,9 +141,14 @@ class QEMUMachine(object):
>>>          qemulog = open(self._qemu_log_path, 'wb')
>>>          try:
>>>              self._pre_launch()
>>> -            args = self._wrapper + [self._binary] + self._base_args() + 
>>> self._args
>>> -            self._popen = subprocess.Popen(args, stdin=devnull, 
>>> stdout=qemulog,
>>> -                                           stderr=subprocess.STDOUT, 
>>> shell=False)
>>> +            self._qemu_full_args = None
>>> +            self._qemu_full_args = (self._wrapper + [self._binary] +
>>> +                                    self._base_args() + self._args)
>>
>> Why set self._qemu_full_args twice?
>
> If it's not cleaned up and an exception happens in
> "self._qemu_full_args = (self._wrapper ...", the message logged in the
> "except" will expose an outdated version of it.

Ignorant question: why aren't we cleaning it up?

>>> +            self._popen = subprocess.Popen(self._qemu_full_args,
>>> +                                           stdin=devnull,
>>> +                                           stdout=qemulog,
>>> +                                           stderr=subprocess.STDOUT,
>>> +                                           shell=False)
>>>              self._post_launch()
>>>          except:
>>>              if self.is_running():
>>> @@ -163,8 +169,9 @@ class QEMUMachine(object):
>>>
>>>              exitcode = self._popen.wait()
>>>              if exitcode < 0:
>>> -                LOG.error('qemu received signal %i: %s', -exitcode,
>>> -                          ' '.join(self._args))
>>> +                LOG.error('qemu received signal %i:%s', -exitcode,
>>> +                          ' Command: %r.' % ' '.join(self._qemu_full_args)
>>> +                          if self._qemu_full_args else '')
>>
>> The last argument is hard to read.
>
> Ok, I'm making it easier.
>
>>
>>>              self._load_io_log()
>>>              self._post_shutdown()
>>
>> The subprocess module appears to keep track of the full command with
>> methods check_call() and check_output(): its in exception
>> CalledProcessError right when you need it.  Sadly, it doesn't appear to
>> be tracked with method Popen().
>
> Indeed.