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From: =?UTF-8?Q?Andreas_F=c3=a4rber?= <afaerber@suse.de>
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Date: Tue, 29 Sep 2015 18:22:53 +0200
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Subject: Re: [Qemu-devel] [PATCH v4 6/7] qdev: Protect
 device-list-properties against broken devices
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To: Markus Armbruster <armbru@redhat.com>, qemu-devel@nongnu.org
Cc: Peter Maydell <peter.maydell@linaro.org>, Anthony Green <green@moxielogic.com>, Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>, Blue Swirl <blauwirbel@gmail.com>, Max Filippov <jcmvbkbc@gmail.com>, "Edgar E. Iglesias" <edgar.iglesias@gmail.com>, Guan Xuetao <gxt@mprc.pku.edu.cn>, Jia Liu <proljc@gmail.com>, Alexander Graf <agraf@suse.de>, Christian Borntraeger <borntraeger@de.ibm.com>, Leon Alrae <leon.alrae@imgtec.com>, thuth@redhat.com, ehabkost@redhat.com, qemu-stable@nongnu.org, stefanha@redhat.com, Cornelia Huck <cornelia.huck@de.ibm.com>, Richard Henderson <rth@twiddle.net>, Bastian Koppelmann <kbastian@mail.uni-paderborn.de>, Michael Walle <michael@walle.cc>, qemu-ppc@nongnu.org, Paolo Bonzini <pbonzini@redhat.com>, Aurelien Jarno <aurelien@aurel32.net>

Am 28.09.2015 um 22:08 schrieb Markus Armbruster:
> Several devices don't survive object_unref(object_new(T)): they crash
> or hang during cleanup, or they leave dangling pointers behind.
>=20
> This breaks at least device-list-properties, because
> qmp_device_list_properties() needs to create a device to find its
> properties.  Broken in commit f4eb32b "qmp: show QOM properties in
> device-list-properties", v2.1.  Example reproducer:
>=20
>     $ qemu-system-aarch64 -nodefaults -display none -machine none -S -q=
mp stdio
>     {"QMP": {"version": {"qemu": {"micro": 50, "minor": 4, "major": 2},=
 "package": ""}, "capabilities": []}}
>     { "execute": "qmp_capabilities" }
>     {"return": {}}
>     { "execute": "device-list-properties", "arguments": { "typename": "=
pxa2xx-pcmcia" } }
>     qemu-system-aarch64: /home/armbru/work/qemu/memory.c:1307: memory_r=
egion_finalize: Assertion `((&mr->subregions)->tqh_first =3D=3D ((void *)=
0))' failed.
>     Aborted (core dumped)
>     [Exit 134 (SIGABRT)]
>=20
> Unfortunately, I can't fix the problems in these devices right now.
> Instead, add DeviceClass member cannot_even_create_with_object_new_yet
> to mark them:

This name is very misleading unfortunately. You must be able to create
any QOM object with object_new(), you just can't clean them up IIUC.

What about cannot_clean_up_with_finalize_yet or irreversible_to_create?

ACK for the general approach of adding a new ugly field. ;)

Regards,
Andreas

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