From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:42120) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1daEyU-0001hD-MB for qemu-devel@nongnu.org; Wed, 26 Jul 2017 01:35:11 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1daEyT-0002Nk-BS for qemu-devel@nongnu.org; Wed, 26 Jul 2017 01:35:10 -0400 Date: Wed, 26 Jul 2017 15:24:43 +1000 From: David Gibson Message-ID: <20170726052443.GF8978@umbus.fritz.box> References: <150100547373.27487.3154210751350595400.stgit@bahia> <150100564746.27487.5195312465666688402.stgit@bahia> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="czsrKamv0OtYjSMr" Content-Disposition: inline In-Reply-To: <150100564746.27487.5195312465666688402.stgit@bahia> Subject: Re: [Qemu-devel] [for-2.11 PATCH 13/26] qdev: store DeviceState's canonical path to use when unparenting List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Greg Kurz Cc: qemu-devel@nongnu.org, "Michael S. Tsirkin" , Michael Roth , qemu-ppc@nongnu.org, Bharata B Rao , Paolo Bonzini , Daniel Henrique Barboza --czsrKamv0OtYjSMr Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Tue, Jul 25, 2017 at 08:00:47PM +0200, Greg Kurz wrote: > From: Michael Roth >=20 > device_unparent(dev, ...) is called when a device is unparented, > either directly, or as a result of a parent device being > finalized, and handles some final cleanup for the device. Part > of this includes emiting a DEVICE_DELETED QMP event to notify > management, which includes the device's path in the composition > tree as provided by object_get_canonical_path(). >=20 > object_get_canonical_path() assumes the device is still connected > to the machine/root container, and will assert otherwise, but > in some situations this isn't the case: >=20 > If the parent is finalized as a result of object_unparent(), it > will still be attached to the composition tree at the time any > children are unparented as a result of that same call to > object_unparent(). However, in some cases, object_unparent() > will complete without finalizing the parent device, due to > lingering references that won't be released till some time later. > One such example is if the parent has MemoryRegion children (which > take a ref on their parent), who in turn have AddressSpace's (which > take a ref on their regions), since those AddressSpaces get cleaned > up asynchronously by the RCU thread. >=20 > In this case qdev:device_unparent() may be called for a child Device > that no longer has a path to the root/machine container, causing > object_get_canonical_path() to assert. >=20 > Fix this by storing the canonical path during realize() so the > information will still be available for device_unparent() in such > cases. Hm. I'm no expert on the QOM model, but I'm not sure this is the right approach. I would have thought the right time to emit the DEVICE_DELETED message would be when the device leaves the main composition tree, even if it could be finalized later. If we made that the case, does this problem go away? > Cc: Michael S. Tsirkin > Cc: Paolo Bonzini > Signed-off-by: Michael Roth > Signed-off-by: Greg Kurz > --- > Changes since RFC: > - rebased against ppc-for-2.10 > --- > hw/core/qdev.c | 15 ++++++++++++--- > include/hw/qdev-core.h | 1 + > 2 files changed, 13 insertions(+), 3 deletions(-) >=20 > diff --git a/hw/core/qdev.c b/hw/core/qdev.c > index 606ab53c42cd..a64b35c16251 100644 > --- a/hw/core/qdev.c > +++ b/hw/core/qdev.c > @@ -928,6 +928,12 @@ static void device_set_realized(Object *obj, bool va= lue, Error **errp) > goto post_realize_fail; > } > =20 > + /* always re-initialize since we clean up in device_unparent() i= nstead > + * of unrealize() > + */ > + g_free(dev->canonical_path); > + dev->canonical_path =3D object_get_canonical_path(OBJECT(dev)); > + > if (qdev_get_vmsd(dev)) { > if (vmstate_register_with_alias_id(dev, -1, qdev_get_vmsd(de= v), dev, > dev->instance_id_alias, > @@ -984,6 +990,7 @@ child_realize_fail: > } > =20 > post_realize_fail: > + g_free(dev->canonical_path); > if (dc->unrealize) { > dc->unrealize(dev, NULL); > } > @@ -1102,10 +1109,12 @@ static void device_unparent(Object *obj) > =20 > /* Only send event if the device had been completely realized */ > if (dev->pending_deleted_event) { > - gchar *path =3D object_get_canonical_path(OBJECT(dev)); > + g_assert(dev->canonical_path); > =20 > - qapi_event_send_device_deleted(!!dev->id, dev->id, path, &error_= abort); > - g_free(path); > + qapi_event_send_device_deleted(!!dev->id, dev->id, dev->canonica= l_path, > + &error_abort); > + g_free(dev->canonical_path); > + dev->canonical_path =3D NULL; > } > =20 > qemu_opts_del(dev->opts); > diff --git a/include/hw/qdev-core.h b/include/hw/qdev-core.h > index ae317286a480..9237b6849ff3 100644 > --- a/include/hw/qdev-core.h > +++ b/include/hw/qdev-core.h > @@ -153,6 +153,7 @@ struct DeviceState { > /*< public >*/ > =20 > const char *id; > + char *canonical_path; > bool realized; > bool pending_deleted_event; > QemuOpts *opts; >=20 --=20 David Gibson | I'll have my music baroque, and my code david AT gibson.dropbear.id.au | minimalist, thank you. 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