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Date: Mon, 13 Feb 2012 02:17:35 +0200
From: "Michael S. Tsirkin" <mst@redhat.com>
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Subject: Re: [Qemu-devel] weird qdev error
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To: Anthony Liguori <anthony@codemonkey.ws>
Cc: qemu-devel@nongnu.org

On Sun, Feb 12, 2012 at 02:19:19PM -0600, Anthony Liguori wrote:
> On 02/12/2012 02:15 PM, Michael S. Tsirkin wrote:
> >On Sun, Feb 12, 2012 at 02:04:29PM -0600, Anthony Liguori wrote:
> >>On 02/12/2012 11:57 AM, Michael S. Tsirkin wrote:
> >>>On Sun, Feb 12, 2012 at 11:38:24AM -0600, Anthony Liguori wrote:
> >>>>From: Anthony Liguori<aliguori@us.ibm.com>
> >>>>Date: Sun, 12 Feb 2012 11:36:24 -0600
> >>>>Subject: [PATCH] device_add: don't add a /peripheral link until init is complete
> >>>>
> >>>>Otherwise we end up with a dangling reference which causes qdev_free() to fail.
> >>>>
> >>>>Reported-by: Michael Tsirkin<mst@redhat.com>
> >>>>Signed-off-by: Anthony Liguori<aliguori@us.ibm.com>
> >>>
> >>>This handles the option parsing but what about hotplug
> >>>failures (when bus->hotplug returns an error)?
> >>
> >>Sorry, I don't follow.
> >>
> >>The assert you reported was that object_free() noted a reference
> >>count of !0 which indicates something else was holding the reference
> >>to the object.  In this case, it was the child link in /peripheral.
> >>
> >>By delaying creating the link in /peripheral, we eliminate the problem completely.
> >
> >Th other problem was internal in pci which calls ->hostplug
> >during initialization. This doesn't seem affected?
> >But I didn't try, maybe I misundertand.
> 
> Yeah, from qdev's perspective it's all just init failing.  hotplug
> is entirely a PCI concept.
> 
> >
> >>BTW, the explicit calls to do_pci_unregister are redundant.
> >>finalize() will be called during cleanup which means exit() will be
> >>invoked (which already calls do_pci_unregister).  I'm not sure why
> >>this isn't failing more aggressively but it looks clearly wrong to
> >>me.
> >>
> >>Regards,
> >>
> >>Anthony Liguori
> >
> >Me too. Want to try to drop them?
> 
> Yeah, I'll make this a two patch series.
> 
> Regards,
> 
> Anthony Liguori


I also see this:

device_add virtio-net-pci,netdev=foo,mac=52:54:00:12:34:56,id=bla
device_del bla
*** glibc detected *** /home/mst/qemu-test/bin/qemu-system-x86_64:
corrupted double-linked list: 0x00007fae434565a0 ***

Am I alone?