From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:36450) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fdesN-00012f-Ka for qemu-devel@nongnu.org; Thu, 12 Jul 2018 12:55:32 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1fdesM-0004P7-Hs for qemu-devel@nongnu.org; Thu, 12 Jul 2018 12:55:31 -0400 References: <1531409463-3843-1-git-send-email-thuth@redhat.com> <1531409463-3843-2-git-send-email-thuth@redhat.com> <20180712165224.GD31657@localhost.localdomain> From: Thomas Huth Message-ID: <224a0bbb-9dbb-87eb-9e9b-1c82923010b5@redhat.com> Date: Thu, 12 Jul 2018 18:55:20 +0200 MIME-Version: 1.0 In-Reply-To: <20180712165224.GD31657@localhost.localdomain> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH 1/5] qom/object: Add a new function object_initialize_as_child() List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Eduardo Habkost Cc: qemu-devel@nongnu.org, Peter Maydell , Paolo Bonzini , qemu-arm@nongnu.org, Markus Armbruster On 12.07.2018 18:52, Eduardo Habkost wrote: > On Thu, Jul 12, 2018 at 05:30:59PM +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 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(). >> >> Signed-off-by: Thomas Huth >> --- >> include/qom/object.h | 19 +++++++++++++++++++ >> qom/object.c | 14 ++++++++++++++ >> 2 files changed, 33 insertions(+) >> >> diff --git a/include/qom/object.h b/include/qom/object.h >> index f3d2308..c1b254c 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_as_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 area >> + * >> + * 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, and will be finalized when the last reference is >> + * dropped. >> + */ >> +void object_initialize_as_child(Object *parentobj, const char *propname, >> + void *childobj, size_t size, const char *type, >> + Error **errp); > > Why did you use void* instead of Object*? That's the same what object_initialize() is doing (see above). Otherwise all the callers have to cast their pointers with OBJECT() first. Thomas