[Libguestfs] Using guestfs.kill_subprocess()

[Richard W.M. Jones]

On Thu, Nov 03, 2011 at 09:41:40PM -0400, Chris Lalancette wrote:
> Hey Rich,
>      In the past I know you have mentioned that using
> guestfs.kill_subprocess() isn't strictly necessary after you are finished
> using libguestfs.  I believe you said that in the python bindings, that
> step would happen automatically when the object goes out of scope and the
> __del__ method is called.  However, since it never seemed to harm anything
> and I wanted to be extra safe, I always called guestfs.kill_subprocess() in
> Oz, without apparent harm.

Python bindings now have an explicit close call:

8c5bdc3e12947580e91c018b71adf9ad3128bb75
http://bugzilla.redhat.com/717786

>      However, Richard Su has been investigating an issue where
> guestfs.kill_subprocess() actually does cause harm.  I believe the
> situation is that running Oz (and hence libguestfs) simultaneously from two
> threads in the same process causes the entire process to hang.  If we
> remove the guestfs.kill_subprocess(), the problem goes away.  rwsu, can you
> please fill in a bit more detail here, as I'm not intimately familiar with
> the issue?  Things like host OS, libguestfs version, etc etc would be
> helpful.  Also confirmation that the problem is indeed in the
> multi-threaded environment of the image factory like I think it is.
>      rjones, do you have any ideas here?  I'm going to merge rwsu's patch
> to remove the call to kill_subprocess(), but I thought it would be worth a
> little more digging into why it was happening.

You could be hitting this bug:
http://bugzilla.redhat.com/684980

To debug this I need to see:

 - version of libguestfs

 - platform that you're running it on

 - full output with LIBGUESTFS_TRACE=1 LIBGUESTFS_DEBUG=1 set

Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
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