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From: Cole Robinson <crobinso@redhat.com>
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Subject: Re: [Qemu-devel] qemu 2.0.0-rc2 crash
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To: Marcel Apfelbaum <marcel.a@redhat.com>, =?UTF-8?B?TWFyY2luIEdpYnXFgmE=?= <m.gibula@beyond.pl>
Cc: qemu-devel@nongnu.org, Stefan Hajnoczi <stefanha@redhat.com>, =?UTF-8?B?QW5kcmVhcyBGw6RyYmVy?= <afaerber@suse.de>

On 04/10/2014 12:39 PM, Marcel Apfelbaum wrote:
> On Thu, 2014-04-10 at 18:24 +0200, Marcin Gibu=C5=82a wrote:
>> W dniu 2014-04-10 15:43, Marcel Apfelbaum pisze:
>>> On Thu, 2014-04-10 at 14:55 +0200, Marcin Gibu=C5=82a wrote:
>>>> Hi,
>>>>
>>>> I've been playing with QEMU 2.0-rc2 and found a crash that isn't the=
re
>>>> in 1.7.1.
>>> Hi Marcin,
>>> Thanks for reporting the bug!
>>>
>>> Do you have a development environment?
>>> If you do, and the reproduction is fast (and you already have a setup=
),
>>> a git bisect to find the problematic commit would be appreciated,
>>
>> Hi,
>>
>> yes, it's on development environment. If you could point me to some=20
>> quick guide to bisecting qemu, I'll be happy to do it.
>=20
> Sure! Thanks for helping.
>=20
> 1. Start:
>      git bisect start
>      git bisect good <commit hash or tag name of the version that works=
> (Ex: v1.7.1)
>      git bisect bad <commit hash or tag name of the non working version=
> (Ex: HEAD)
> 2. Git will checkout commits for you and you have to check and answer:
>      git bisect good or git bisect bad=20
> 3. Git will show you the first bad commit.
>=20
> A more detailed version here:
> http://git-scm.com/book/en/Git-Tools-Debugging-with-Git
> Look for git-bisect.

Actually I was just independently bisecting this :) Culprit is:

commit 9561fda8d90e176bef598ba87c42a1bd6ad03ef7
Author: Stefan Hajnoczi <stefanha@redhat.com>
Date:   Wed Mar 19 08:58:55 2014 +0100

    qom: Make QOM link property unref optional

Simple reproducer:

./x86_64-softmmu/qemu-system-x86_64 -qmp unix:./qmp.sock,server

./scripts/qmp/qmp-shell ./qmp.sock
(QEMU) qom-list path=3D//machine/i440fx/pci.0/child[2]

Seems like trying to qom-list any link property will crash

- Cole