From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id ED01DD6E2CA for ; Thu, 21 Nov 2024 10:22:30 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1tE4K9-0005Kh-DW; Thu, 21 Nov 2024 05:22:09 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1tE4K7-0005KU-Fz for qemu-devel@nongnu.org; Thu, 21 Nov 2024 05:22:07 -0500 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1tE4K4-0002TJ-OW for qemu-devel@nongnu.org; Thu, 21 Nov 2024 05:22:06 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1732184523; h=from:from:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:in-reply-to:in-reply-to: references:references; bh=XaycezCz2rBOur+KyWEmyt37RPzEtdFKrQfYQPbOyFw=; b=XuZlRG7baSKGk5c2hButf5125vKBqCXw29MGGSbwXg7kkxb/MEREEGndLBdOA6DbjAm0sO saVfuo0gPVz7ZXyAIxD7TjXD+PmR49JIbl4GSj/bZM/1y3eoSFFzd5tBISO0TJaPY3tDxo CA4YliLS/UW9ce3OVmQPQCLxwlrwsdg= Received: from mx-prod-mc-04.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-328-WKgQWEevMLqifuvcIw1oFg-1; Thu, 21 Nov 2024 05:21:59 -0500 X-MC-Unique: WKgQWEevMLqifuvcIw1oFg-1 X-Mimecast-MFC-AGG-ID: WKgQWEevMLqifuvcIw1oFg Received: from mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.17]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-04.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 4DA4619560AF; Thu, 21 Nov 2024 10:21:58 +0000 (UTC) Received: from redhat.com (unknown [10.42.28.5]) by mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 4D90619560A3; Thu, 21 Nov 2024 10:21:52 +0000 (UTC) Date: Thu, 21 Nov 2024 10:21:48 +0000 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Peter Xu Cc: qemu-devel@nongnu.org, Eduardo Habkost , Peter Maydell , Markus Armbruster , Juraj Marcin , Philippe =?utf-8?Q?Mathieu-Daud=C3=A9?= , =?utf-8?Q?C=C3=A9dric?= Le Goater , Paolo Bonzini , Fabiano Rosas Subject: Re: [PATCH 08/12] qdev: Make qdev_get_machine() not use container_get() Message-ID: References: <20241120215703.3918445-1-peterx@redhat.com> <20241120215703.3918445-9-peterx@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20241120215703.3918445-9-peterx@redhat.com> User-Agent: Mutt/2.2.12 (2023-09-09) X-Scanned-By: MIMEDefang 3.0 on 10.30.177.17 Received-SPF: pass client-ip=170.10.133.124; envelope-from=berrange@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -21 X-Spam_score: -2.2 X-Spam_bar: -- X-Spam_report: (-2.2 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.143, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, RCVD_IN_VALIDITY_SAFE_BLOCKED=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On Wed, Nov 20, 2024 at 04:56:59PM -0500, Peter Xu wrote: > Currently, qdev_get_machine() has a slight misuse on container_get(), as > the helper says "get a container" but in reality the goal is to get the > machine object. It is still a "container" but not strictly. > > Note that it _may_ get a container (at "/machine") in our current unit test > of test-qdev-global-props.c before all these changes, but it's probably > unexpected and worked by accident. > > Switch to an explicit object_resolve_path_component(), with a side benefit > that qdev_get_machine() can happen a lot, and we don't need to split the > string ("/machine") every time. This also paves way for making the helper > container_get() never try to return a non-container at all. > > Signed-off-by: Peter Xu > --- > hw/core/qdev.c | 8 +++++++- > 1 file changed, 7 insertions(+), 1 deletion(-) > > diff --git a/hw/core/qdev.c b/hw/core/qdev.c > index 5f13111b77..c869c47a27 100644 > --- a/hw/core/qdev.c > +++ b/hw/core/qdev.c > @@ -817,7 +817,13 @@ Object *qdev_get_machine(void) > static Object *dev; > > if (dev == NULL) { > - dev = container_get(object_get_root(), "/machine"); > + /* > + * NOTE: when the machine is not yet created, this helper will > + * also keep the cached object untouched and return NULL. The next > + * invoke of the helper will try to look for the machine again. > + * It'll only cache the pointer when it's found the first time. > + */ This smells like a recipe for subtle bugs. I think I'd consider it a code flaw if something called qdev_get_machine() in a scenario where the machine does not yet exist. > + dev = object_resolve_path_component(object_get_root(), "machine"); > } IOW, I think we should assert that dev != NULL to ensure we immediately diagnose the flawed sequence of calls. With regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|