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 X-Spam-Level: X-Spam-Status: No, score=-3.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9FE67C433E0 for ; Thu, 14 Jan 2021 14:26:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 75D6C23A57 for ; Thu, 14 Jan 2021 14:26:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729198AbhANO0H (ORCPT ); Thu, 14 Jan 2021 09:26:07 -0500 Received: from mga02.intel.com ([134.134.136.20]:58501 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726805AbhANO0F (ORCPT ); Thu, 14 Jan 2021 09:26:05 -0500 IronPort-SDR: TDMe6LdtLjRGuZ8lKfkYMxJMTrtDJJSVQTW0w9Bw3CKAG8vWc/MU9SKNG+eKxNNbPyDhmvb+V3 +c5XOCP1MMsg== X-IronPort-AV: E=McAfee;i="6000,8403,9863"; a="165460677" X-IronPort-AV: E=Sophos;i="5.79,347,1602572400"; d="scan'208";a="165460677" Received: from fmsmga001.fm.intel.com ([10.253.24.23]) by orsmga101.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 14 Jan 2021 06:24:19 -0800 IronPort-SDR: wjo3JEq5Z7etD61x5dHXSeFHh6gJJdzfdd8jSXbekk17AFuZU32aQSpp8aQeDKH6fHgIo3tbYl s4MX/Mzh9VFA== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.79,347,1602572400"; d="scan'208";a="465266602" Received: from kuha.fi.intel.com ([10.237.72.162]) by fmsmga001.fm.intel.com with SMTP; 14 Jan 2021 06:24:16 -0800 Received: by kuha.fi.intel.com (sSMTP sendmail emulation); Thu, 14 Jan 2021 16:24:15 +0200 Date: Thu, 14 Jan 2021 16:24:15 +0200 From: Heikki Krogerus To: Andy Shevchenko Cc: Daniel Scally , Felipe Balbi , "Rafael J. Wysocki" , linux-kernel@vger.kernel.org, linux-usb@vger.kernel.org, linux-acpi@vger.kernel.org Subject: Re: [PATCH v2 1/3] software node: Introduce device_add_software_node() Message-ID: <20210114142415.GC2864731@kuha.fi.intel.com> References: <20210111141045.14027-1-heikki.krogerus@linux.intel.com> <20210111141045.14027-2-heikki.krogerus@linux.intel.com> <2f552de5-4839-a1e5-3012-c56f9fa3bdd5@gmail.com> <20210113113918.GA2584629@kuha.fi.intel.com> <20210113153003.GR4077@smile.fi.intel.com> <20210114131948.GA2864731@kuha.fi.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210114131948.GA2864731@kuha.fi.intel.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jan 14, 2021 at 03:19:52PM +0200, Heikki Krogerus wrote: > On Wed, Jan 13, 2021 at 05:30:03PM +0200, Andy Shevchenko wrote: > > On Wed, Jan 13, 2021 at 01:39:18PM +0200, Heikki Krogerus wrote: > > > On Wed, Jan 13, 2021 at 12:40:03AM +0000, Daniel Scally wrote: > > > > On 11/01/2021 14:10, Heikki Krogerus wrote: > > > > ... > > > > > > > +/** > > > > > + * device_remove_software_node - Remove device's software node > > > > > + * @dev: The device with the software node. > > > > > + * > > > > > + * This function will unregister the software node of @dev. > > > > > + */ > > > > > +void device_remove_software_node(struct device *dev) > > > > > +{ > > > > > + struct swnode *swnode; > > > > > + > > > > > + swnode = dev_to_swnode(dev); > > > > > + if (!swnode) > > > > > + return; > > > > > + > > > > > + kobject_put(&swnode->kobj); > > > > > +} > > > > > +EXPORT_SYMBOL_GPL(device_remove_software_node); > > > > > > > > I wonder if this also ought to set dev_fwnode(dev)->secondary back to > > > > ERR_PTR(-ENODEV)? > > > > Actually it's a good question. > > > > > We can't do that here unfortunately. Other places still have a > > > reference to the swnode at this point and they may still need to > > > access it using the dev_fwnode(dev)->secondary pointer. > > > > Yeah, but in this case we potentially leave a dangling pointer when last of the > > user gone and kobject_put() will call for release. > > The caller has to be responsible of setting the secondary back to > ERR_PTR(-ENODEV). We can not do anything here like I explained. We can > not even do that in software_node_notify() when the association to the > struct device is removed, because the fwnode->secondary is still > accessed after that. The caller needs to remove both the node and the > device, and only after that it is safe to set the secondary back to > ERR_PTR(-ENODEV). I studied the code again, and it actually looks like this is only a problem when device_add_properties() is used and there is an expectation that the node/properties are removed automatically in device_del(). When this new API is used, the only place that needs to access the swnode using the secondary pointer is software_node_notify(), so if we simply handle that separately here, we should be able to clear the secondary pointer after all. It would look something like this: void device_remove_software_node(struct device *dev) { struct swnode *swnode; swnode = dev_to_swnode(dev); if (!swnode) return; software_node_notify(dev, KOBJ_REMOVE); set_secondary_fwnode(dev, NULL); kobject_put(&swnode->kobj); } I'll test that, and if it works, and you guys don't see any problems with it, I'll use it in v3. Br, -- heikki