Re: [Qemu-devel] [PATCH v2 1/3] qemu.py: fix is_running()

[Eduardo Habkost <ehabkost@redhat.com>]

On Wed, Jul 19, 2017 at 06:31:06PM +0200, Amador Pahim wrote:
> Current implementation is broken. It does not really test if the child
> process is running.
> 
> The Popen.returncode will only be set after by a poll(), wait() or
> communicate(). If the Popen fails to launch a VM, the Popen.returncode
> will not turn to None by itself.
> 
> Instead of using Popen.returncode, let's use Popen.poll(), which
> actually checks if child process has terminated.
> 
> Signed-off-by: Amador Pahim <apahim@redhat.com>

I vaguely remember I had a version of that code using poll() and
it broke scripts for some reason.  I will try to find out why, so
we can either fix the script or document the reason why poll()
isn't a good choice here.

> ---
>  scripts/qemu.py | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/scripts/qemu.py b/scripts/qemu.py
> index 880e3e8219..f0fade32bd 100644
> --- a/scripts/qemu.py
> +++ b/scripts/qemu.py
> @@ -86,7 +86,7 @@ class QEMUMachine(object):
>              raise
>  
>      def is_running(self):
> -        return self._popen and (self._popen.returncode is None)
> +        return self._popen and (self._popen.poll() is None)
>  
>      def exitcode(self):
>          if self._popen is None:
> -- 
> 2.13.3
> 

-- 
Eduardo