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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1EB10C433F5 for ; Sat, 26 Mar 2022 13:04:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233019AbiCZNGK (ORCPT ); Sat, 26 Mar 2022 09:06:10 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42380 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231591AbiCZNGJ (ORCPT ); Sat, 26 Mar 2022 09:06:09 -0400 Received: from bmailout1.hostsharing.net (bmailout1.hostsharing.net [IPv6:2a01:37:1000::53df:5f64:0]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1054C52E21 for ; Sat, 26 Mar 2022 06:04:31 -0700 (PDT) Received: from h08.hostsharing.net (h08.hostsharing.net [IPv6:2a01:37:1000::53df:5f1c:0]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client CN "*.hostsharing.net", Issuer "RapidSSL TLS DV RSA Mixed SHA256 2020 CA-1" (verified OK)) by bmailout1.hostsharing.net (Postfix) with ESMTPS id 2B0283000034F; Sat, 26 Mar 2022 14:04:30 +0100 (CET) Received: by h08.hostsharing.net (Postfix, from userid 100393) id 1D7DF2E6C12; Sat, 26 Mar 2022 14:04:30 +0100 (CET) Date: Sat, 26 Mar 2022 14:04:30 +0100 From: Lukas Wunner To: Andrew Lunn Cc: Oleksij Rempel , Oliver Neukum , Oleksij Rempel , "netdev@vger.kernel.org" , Heiner Kallweit Subject: Re: ordering of call to unbind() in usbnet_disconnect Message-ID: <20220326130430.GD31022@wunner.de> References: <20220314184234.GA556@wunner.de> <20220315054403.GA14588@pengutronix.de> <20220315083234.GA27883@wunner.de> <20220315113841.GA22337@pengutronix.de> <20220321100226.GA19177@wunner.de> <20220326123929.GB31022@wunner.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Sat, Mar 26, 2022 at 01:49:28PM +0100, Andrew Lunn wrote: > On Sat, Mar 26, 2022 at 01:39:29PM +0100, Lukas Wunner wrote: > > On Mon, Mar 21, 2022 at 02:10:27PM +0100, Andrew Lunn wrote: > > > There are two patterns in use at the moment: > > > > > > 1) The phy is attached in open() and detached in close(). There is no > > > danger of the netdev disappearing at this time. > > > > > > 2) The PHY is attached during probe, and detached during release. > > > > > > This second case is what is being used here in the USB code. This is > > > also a common pattern for complex devices. In probe, you get all the > > > components of a complex devices, stitch them together and then > > > register the composite device. During release, you unregister the > > > composite device, and then release all the components. Since this is a > > > natural model, i think it should work. > > > > I've gone through all drivers and noticed that some of them use a variation > > of pattern 2 which looks fishy: > > > > On probe, they first attach the PHY, then register the netdev. > > On remove, they detach the PHY, then unregister the netdev. > > > > Is it legal to detach the PHY from a registered (potentially running) > > netdev? It looks wrong to me. > > I think the network stack guarantee that the close() method is called > before unregister completes. It is a common pattern to attach the PHY > in open() and detach it in close(). The stack itself should not be > using the PHY when it is down, the exception being IOCTL handlers > which people often get wrong. But the PHY is detached from a *running* netdev *before* that netdev is unregistered (and closed). Is that really legal? Thanks, Lukas