From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933150AbcKQQ71 (ORCPT ); Thu, 17 Nov 2016 11:59:27 -0500 Received: from mail-qk0-f196.google.com ([209.85.220.196]:34785 "EHLO mail-qk0-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932790AbcKQQ7Y (ORCPT ); Thu, 17 Nov 2016 11:59:24 -0500 Date: Thu, 17 Nov 2016 17:47:34 +0100 From: Johan Hovold To: Florian Fainelli Cc: Johan Hovold , Andrew Lunn , Vivien Didelot , "David S. Miller" , netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] net: dsa: fix fixed-link-phy device leaks Message-ID: <20161117164734.GC10490@localhost> References: <1479307664-32428-1-git-send-email-johan@kernel.org> <42af57ed-df84-f628-659d-c982d30da7d5@gmail.com> <20161116171145.GE4864@localhost> <8387696c-813a-4c88-5f10-7d2e5fdae6b8@gmail.com> <20161117095225.GC21237@localhost> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20161117095225.GC21237@localhost> User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Nov 17, 2016 at 10:52:25AM +0100, Johan Hovold wrote: > On Wed, Nov 16, 2016 at 10:14:10AM -0800, Florian Fainelli wrote: > > On 11/16/2016 09:11 AM, Johan Hovold wrote: > > > On Wed, Nov 16, 2016 at 09:06:26AM -0800, Florian Fainelli wrote: > > >> On 11/16/2016 06:47 AM, Johan Hovold wrote: > > >>> Make sure to drop the reference taken by of_phy_find_device() when > > >>> registering and deregistering the fixed-link PHY-device. > > >>> > > >>> Note that we need to put both references held at deregistration. > > >>> > > >>> Fixes: 39b0c705195e ("net: dsa: Allow configuration of CPU & DSA port > > >>> speeds/duplex") > > >>> Signed-off-by: Johan Hovold > > >>> --- > > >>> > > >>> Hi, > > >>> > > >>> This is one has been compile tested only, but fixes a couple of leaks > > >>> similar to one that was found in the cpsw driver for which I just posted > > >>> a patch. > > >>> > > >>> It turns out all drivers but DSA fail to deregister the fixed-link PHYs > > >>> registered by of_phy_register_fixed_link(). Due to the way this > > >>> interface was designed, deregistering such a PHY is a bit cumbersome and > > >>> looks like it would benefit from a common helper. > > >>> > > >>> However, perhaps the interface should instead be changed so that the PHY > > >>> device is returned so that drivers do not need to use > > >>> of_phy_find_device() when they need to access properties of the fixed > > >>> link (e.g. as in dsu_cpu_dsa_setup below). > > >>> > > >>> Thoughts? > > >>> > > >>> Thanks, > > >>> Johan > > >>> > > >>> > > >>> net/dsa/dsa.c | 8 +++++++- > > >>> 1 file changed, 7 insertions(+), 1 deletion(-) > > >>> > > >>> diff --git a/net/dsa/dsa.c b/net/dsa/dsa.c > > >>> index a6902c1e2f28..798a6a776a5f 100644 > > >>> --- a/net/dsa/dsa.c > > >>> +++ b/net/dsa/dsa.c > > >>> @@ -233,6 +233,8 @@ int dsa_cpu_dsa_setup(struct dsa_switch *ds, struct device *dev, > > >>> genphy_read_status(phydev); > > >>> if (ds->ops->adjust_link) > > >>> ds->ops->adjust_link(ds, port, phydev); > > >>> + > > >>> + phy_device_free(phydev); /* of_phy_find_device */ > > >>> } > > >>> > > >>> return 0; > > >>> @@ -509,8 +511,12 @@ void dsa_cpu_dsa_destroy(struct device_node *port_dn) > > >>> if (of_phy_is_fixed_link(port_dn)) { > > >>> phydev = of_phy_find_device(port_dn); > > >>> if (phydev) { > > >>> - phy_device_free(phydev); > > >>> fixed_phy_unregister(phydev); > > >>> + /* Put references taken by of_phy_find_device() and > > >>> + * of_phy_register_fixed_link(). > > >>> + */ > > >>> + phy_device_free(phydev); > > >>> + phy_device_free(phydev); > > >> > > >> Double free, this looks bogus here. Actually would not this mean a > > >> triple free since you already free in dsa_cpu_dsa_setup() which is > > >> paired with dsa_cpu_dsa_destroy()? > > > > > > The naming of phy_device_free() is unfortunate when it's really a put(): > > > > > > void phy_device_free(struct phy_device *phydev) > > > { > > > put_device(&phydev->mdio.dev); > > > } > > > > Indeed, should have looked a little harder. > > > > > > > > which may need to be called multiple times, specifically after a call to > > > of_phy_find_device() which takes another reference. > > > > > > With this patch the refcounts are properly balanced. > > > > The intent of your patch is good, but it still feels like having to > > double imbalance the refcount is symptomatic of a larger issue here, it > > does not seem like having several refcounts are necessary, so we may > > really want to rework the API. > > I'll cook something up for -next, but how about using > > put_device(&phydev->mdio.dev) > > for the reference taken by of_phy_find_device() (as some driver > already do) to fix the immediate leaks? > > Then deregistration would look like: > > phydev = of_phy_find_device(port_dn); > if (phydev) { > - phy_device_free(phydev); > fixed_phy_unregister(phydev); > + put_device(&phydev->mdio.dev) > + phy_device_free(phydev); On second thought, I suggest just renaming the phy_device_free() as phy_device_put() to reflect what it really does these days. There can never be a guarantee that the phy is freed on a call to phy_device_free() anyway. The OF interface can still be modified to return a pointer later. Johan