From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:40262) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fdtQh-00029v-Bt for qemu-devel@nongnu.org; Fri, 13 Jul 2018 04:27:56 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1fdtQg-0004E9-5Y for qemu-devel@nongnu.org; Fri, 13 Jul 2018 04:27:55 -0400 From: Thomas Huth Date: Fri, 13 Jul 2018 10:27:29 +0200 Message-Id: <1531470464-21522-2-git-send-email-thuth@redhat.com> In-Reply-To: <1531470464-21522-1-git-send-email-thuth@redhat.com> References: <1531470464-21522-1-git-send-email-thuth@redhat.com> Subject: [Qemu-devel] [PATCH v2 01/16] qom/object: Add a new function object_initialize_child() List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org, Peter Maydell , Paolo Bonzini Cc: qemu-arm@nongnu.org, Markus Armbruster , Eduardo Habkost , Beniamino Galvani , Subbaraya Sundeep , Alistair Francis , "Edgar E. Iglesias" , =?UTF-8?q?Andreas=20F=C3=A4rber?= 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 introdcue 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 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 | 23 +++++++++++++++++++++-- qom/object.c | 15 +++++++++++++++ 2 files changed, 36 insertions(+), 2 deletions(-) diff --git a/include/qom/object.h b/include/qom/object.h index f3d2308..3362db0 100644 --- a/include/qom/object.h +++ b/include/qom/object.h @@ -749,6 +749,25 @@ 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 @obj 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 + * + * 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 get finalized automatically when the parent gets removed. + */ +void object_initialize_child(Object *parentobj, const char *propname, + void *childobj, size_t size, const char *type, + Error **errp); + +/** * object_dynamic_cast: * @obj: The object to cast. * @typename: The @typename to cast to. @@ -1382,7 +1401,7 @@ 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 +1439,7 @@ 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..7be7638 100644 --- a/qom/object.c +++ b/qom/object.c @@ -392,6 +392,21 @@ 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) +{ + object_initialize(childobj, size, type); + object_property_add_child(parentobj, propname, OBJECT(childobj), errp); + /* + * 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(OBJECT(childobj)); +} + + static inline bool object_property_is_child(ObjectProperty *prop) { return strstart(prop->type, "child<", NULL); -- 1.8.3.1