Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757009AbbKRUkB (ORCPT ); Wed, 18 Nov 2015 15:40:01 -0500 Received: from mail3-relais-sop.national.inria.fr ([192.134.164.104]:27014 "EHLO mail3-relais-sop.national.inria.fr" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756843AbbKRUj6 (ORCPT ); Wed, 18 Nov 2015 15:39:58 -0500 X-IronPort-AV: E=Sophos;i="5.20,314,1444687200"; d="scan'208";a="154315997" Date: Wed, 18 Nov 2015 21:39:54 +0100 (CET) From: Julia Lawall X-X-Sender: jll@localhost6.localdomain6 To: Brian Norris cc: Julia Lawall , Kishon Vijay Abraham I , kernel-janitors@vger.kernel.org, Gregory Fong , Florian Fainelli , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Russell King - ARM Linux , Thomas Petazzoni , Andrew Lunn , Bjorn Helgaas , Jason Cooper , devicetree@vger.kernel.org Subject: Re: device_node lifetime (was: Re: [PATCH 1/7] phy: brcmstb-sata: add missing of_node_put) In-Reply-To: <20151118190500.GE140057@google.com> Message-ID: References: <1447673600-8881-1-git-send-email-Julia.Lawall@lip6.fr> <1447673600-8881-2-git-send-email-Julia.Lawall@lip6.fr> <20151117013830.GV8456@google.com> <20151117174430.GA8456@google.com> <20151117183036.GF8456@google.com> <20151118190500.GE140057@google.com> User-Agent: Alpine 2.02 (DEB 1266 2009-07-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2839 Lines: 80 On Wed, 18 Nov 2015, Brian Norris wrote: > (changing subject, add devicetree@vger.kernel.org) > > On Tue, Nov 17, 2015 at 11:33:25PM +0100, Julia Lawall wrote: > > On Tue, 17 Nov 2015, Brian Norris wrote: > > > On Tue, Nov 17, 2015 at 06:48:39PM +0100, Julia Lawall wrote: > > > > Is this something that should be checked for elsewhere? > > > > > > I expect the same sort of problem shows up plenty of other places. I > > > don't think many people use CONFIG_OF_DYNAMIC, so the effects of these > > > failures probably aren't felt by many. > > > > I tried the following semantic patch: > > > > @@ > > struct device_node *e; > > expression e1; > > identifier fld; > > @@ > > > > ... when != of_node_get(...) > > *(<+...e1->fld...+>) = e > > ... when != of_node_get(...) > > return e1; > > > > basically, this says that a structure field is initilized to a device node > > value, the structure is returned by the containing function, and the > > containing function contains no of_node_get at all. Certainly this is > > quite constrained, but it does produce a number of examples. > > > > I looked at a few of them: > > > > drivers/clk/ingenic/cgu.c, ingenic_cgu_new > > clk/pistachio/clk.c, pistachio_clk_alloc_provider > > It looks like the clock core (drivers/clk/clk.c) initially grabs the clk > provider node in of_clk_init(), then drops it after it's initialized, > but most of these providers use of_clk_add_provider(), which seems to > manage the device_node lifetime for the user. So I think these are OK. > > > drivers/mfd/syscon.c, of_syscon_register > > This one looks potentially suspect. Syscon nodes aren't usually directly > managed by a single driver, and the device_node pointer is used for > lookups later...so I think it should keep a kref, and it doesn't. > > > drivers/of/pdt.c, function of_pdt_create_node > > Not real sure about this one. > > > Any idea whether these need of_node_get? In all cases the device node > > value comes in as a parameter. > > I'm really not an expert on this stuff. I just saw a potential problem > that I happen to be looking at in other subsystems, and I wanted to know > what others thought. Thanks for the analysis. I will look into them a bit more. Hopefully at least the maintainer of each file will know what should be done. julia > I think this discussion should include the DT folks > and the subsystems in question. For one, I'm as interested as anyone in > getting this todo clarified: > > Documentation/devicetree/todo.txt > - Document node lifecycle for CONFIG_OF_DYNAMIC > > Regards, > Brian > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/