From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:48067) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ffAhi-0002RJ-Kl for qemu-devel@nongnu.org; Mon, 16 Jul 2018 17:06:48 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ffAhh-00052q-4K for qemu-devel@nongnu.org; Mon, 16 Jul 2018 17:06:46 -0400 Date: Mon, 16 Jul 2018 18:06:36 -0300 From: Eduardo Habkost Message-ID: <20180716210636.GS31657@localhost.localdomain> References: <1531745974-17187-1-git-send-email-thuth@redhat.com> <1531745974-17187-2-git-send-email-thuth@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1531745974-17187-2-git-send-email-thuth@redhat.com> Subject: Re: [Qemu-devel] [PATCH v3 01/17] qom/object: Add a new function object_initialize_child() List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Thomas Huth Cc: qemu-devel@nongnu.org, Peter Maydell , Paolo Bonzini , qemu-arm@nongnu.org, Markus Armbruster , Beniamino Galvani , Subbaraya Sundeep , Alistair Francis , "Edgar E. Iglesias" , Andreas =?iso-8859-1?Q?F=E4rber?= On Mon, Jul 16, 2018 at 02:59:18PM +0200, Thomas Huth wrote: > A lot of code is using the object_initialize() function followed by a call > to object_property_add_child() to add the newly initialized object as a child > of the current object. Both functions increase the reference counter of the > new object, but many spots that call these two functions then forget to drop > one of the superfluous references. So the newly created object is often not > cleaned up correctly when the parent is destroyed. In the worst case, this > can cause crashes, e.g. because device objects are not correctly removed from > their parent_bus. > > Since this is a common pattern between many code spots, let's introduce a > new function that takes care of calling all three required initialization > functions, first object_initialize(), then object_property_add_child() and > finally object_unref(). And since the function does a similar job like > object_new_with_props(), also allow to set additional properties via > varargs, and use user_creatable_complete() to make sure that the functions > can be used similarly. > > And while we're at object.h, also fix some copy-n-paste errors in the > comments there ("to store the area" --> "to store the error"). > > Signed-off-by: Thomas Huth > --- > include/qom/object.h | 45 +++++++++++++++++++++++++++++++++++++++++-- > qom/object.c | 54 ++++++++++++++++++++++++++++++++++++++++++++++++++++ > 2 files changed, 97 insertions(+), 2 deletions(-) > > diff --git a/include/qom/object.h b/include/qom/object.h > index f3d2308..f0b0bf3 100644 > --- a/include/qom/object.h > +++ b/include/qom/object.h > @@ -749,6 +749,47 @@ int object_set_propv(Object *obj, > void object_initialize(void *obj, size_t size, const char *typename); > > /** > + * object_initialize_child: > + * @parentobj: The parent object to add a property to > + * @propname: The name of the property > + * @childobj: A pointer to the memory to be used for the object. > + * @size: The maximum size available at @childobj for the object. > + * @type: The name of the type of the object to instantiate. > + * @errp: If an error occurs, a pointer to an area to store the error > + * @...: list of property names and values > + * > + * This function will initialize an object. The memory for the object should > + * have already been allocated. The object will then be added as child property > + * to a parent with object_property_add_child() function. The returned object > + * has a reference count of 1 (for the "child<...>" property from the parent), > + * so the object will be finalized automatically when the parent gets removed. > + * > + * The variadic parameters are a list of pairs of (propname, propvalue) > + * strings. The propname of %NULL indicates the end of the property list. > + * If the object implements the user creatable interface, the object will > + * be marked complete once all the properties have been processed. > + */ > +void object_initialize_child(Object *parentobj, const char *propname, > + void *childobj, size_t size, const char *type, > + Error **errp, ...) QEMU_SENTINEL; > + > +/** > + * object_initialize_childv: > + * @parentobj: The parent object to add a property to > + * @propname: The name of the property > + * @childobj: A pointer to the memory to be used for the object. > + * @size: The maximum size available at @childobj for the object. > + * @type: The name of the type of the object to instantiate. > + * @errp: If an error occurs, a pointer to an area to store the error > + * @vargs: list of property names and values > + * > + * See object_initialize_child() for documentation. > + */ > +void object_initialize_childv(Object *parentobj, const char *propname, > + void *childobj, size_t size, const char *type, > + Error **errp, va_list vargs); > + > +/** > * object_dynamic_cast: > * @obj: The object to cast. > * @typename: The @typename to cast to. > @@ -1382,7 +1423,7 @@ Object *object_resolve_path_component(Object *parent, const gchar *part); > * @obj: the object to add a property to > * @name: the name of the property > * @child: the child object > - * @errp: if an error occurs, a pointer to an area to store the area > + * @errp: if an error occurs, a pointer to an area to store the error > * > * Child properties form the composition tree. All objects need to be a child > * of another object. Objects can only be a child of one object. > @@ -1420,7 +1461,7 @@ void object_property_allow_set_link(const Object *, const char *, > * @child: a pointer to where the link object reference is stored > * @check: callback to veto setting or NULL if the property is read-only > * @flags: additional options for the link > - * @errp: if an error occurs, a pointer to an area to store the area > + * @errp: if an error occurs, a pointer to an area to store the error > * > * Links establish relationships between objects. Links are unidirectional > * although two links can be combined to form a bidirectional relationship > diff --git a/qom/object.c b/qom/object.c > index 4609e34..75d1d48 100644 > --- a/qom/object.c > +++ b/qom/object.c > @@ -392,6 +392,60 @@ void object_initialize(void *data, size_t size, const char *typename) > object_initialize_with_type(data, size, type); > } > > +void object_initialize_child(Object *parentobj, const char *propname, > + void *childobj, size_t size, const char *type, > + Error **errp, ...) > +{ > + va_list vargs; > + > + va_start(vargs, errp); > + object_initialize_childv(parentobj, propname, childobj, size, type, errp, > + vargs); > + va_end(vargs); > +} > + > +void object_initialize_childv(Object *parentobj, const char *propname, > + void *childobj, size_t size, const char *type, > + Error **errp, va_list vargs) > +{ > + Error *local_err = NULL; > + Object *obj; > + > + object_initialize(childobj, size, type); > + obj = OBJECT(childobj); > + > + object_set_propv(obj, &local_err, vargs); > + if (local_err) { > + goto out; > + } > + > + object_property_add_child(parentobj, propname, obj, &local_err); > + if (local_err) { > + goto out; > + } > + > + if (object_dynamic_cast(obj, TYPE_USER_CREATABLE)) { > + user_creatable_complete(obj, &local_err); > + if (local_err) { > + object_unparent(obj); > + goto out; > + } > + } I don't like adding TYPE_USER_CREATABLE-specific hacks to QOM core, but well, at least this is consistent with object_new_with_propv(). Reviewed-by: Eduardo Habkost > + > + /* > + * Since object_property_add_child added a reference to the child object, > + * we can drop the reference added by object_initialize(), so the child > + * property will own the only reference to the object. > + */ > + object_unref(obj); > + > +out: > + if (local_err) { > + error_propagate(errp, local_err); > + object_unref(obj); > + } > +} > + > static inline bool object_property_is_child(ObjectProperty *prop) > { > return strstart(prop->type, "child<", NULL); > -- > 1.8.3.1 > -- Eduardo