Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753588AbbG2R5D (ORCPT ); Wed, 29 Jul 2015 13:57:03 -0400 Received: from mail-pa0-f48.google.com ([209.85.220.48]:35453 "EHLO mail-pa0-f48.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753373AbbG2R5B (ORCPT ); Wed, 29 Jul 2015 13:57:01 -0400 Date: Wed, 29 Jul 2015 10:56:56 -0700 From: Dmitry Torokhov To: "Dr. H. Nikolaus Schaller" Cc: Rob Herring , Belisko Marek , "linux-input@vger.kernel.org" , LKML , Rob Herring , Grant Likely Subject: Re: [PATCH] input: twl4030-vibra: Fix ERROR: Bad of_node_put() warning Message-ID: <20150729175656.GE23178@dtor-ws> References: <1437683914-4660-1-git-send-email-marek@goldelico.com> <20150723205314.GB12733@dtor-ws>

<20150729172602.GB23178@dtor-ws> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5101 Lines: 93 On Wed, Jul 29, 2015 at 07:50:24PM +0200, Dr. H. Nikolaus Schaller wrote: > > Am 29.07.2015 um 19:26 schrieb Dmitry Torokhov : > > > On Tue, Jul 28, 2015 at 10:13:54PM -0500, Rob Herring wrote: > >> On Tue, Jul 28, 2015 at 3:23 PM, Belisko Marek wrote: > >>> Hi Dmitry, > >>> > >>> On Thu, Jul 23, 2015 at 10:53 PM, Dmitry Torokhov > >>> wrote: > >>>> On Thu, Jul 23, 2015 at 10:38:34PM +0200, Marek Belisko wrote: > >>>>> Fix following: > >>>>> [ 8.862274] ERROR: Bad of_node_put() on /ocp/i2c@48070000/twl@48/audio > >>>>> [ 8.869293] CPU: 0 PID: 1003 Comm: modprobe Not tainted 4.2.0-rc2-letux+ #1175 > >>>>> [ 8.876922] Hardware name: Generic OMAP36xx (Flattened Device Tree) > >>>>> [ 8.883514] [] (unwind_backtrace) from [] (show_stack+0x10/0x14) > >>>>> [ 8.891693] [] (show_stack) from [] (dump_stack+0x78/0x94) > >>>>> [ 8.899322] [] (dump_stack) from [] (kobject_release+0x68/0x7c) > >>>>> [ 8.907409] [] (kobject_release) from [] (twl4030_vibra_probe+0x74/0x188 [twl4030_vibra]) > >>>>> [ 8.917877] [] (twl4030_vibra_probe [twl4030_vibra]) from [] (platform_drv_probe+0x48/0x90) > >>>>> [ 8.928497] [] (platform_drv_probe) from [] (really_probe+0xd4/0x238) > >>>>> [ 8.937103] [] (really_probe) from [] (driver_probe_device+0x30/0x48) > >>>>> [ 8.945678] [] (driver_probe_device) from [] (__driver_attach+0x68/0x8c) > >>>>> [ 8.954589] [] (__driver_attach) from [] (bus_for_each_dev+0x50/0x84) > >>>>> [ 8.963226] [] (bus_for_each_dev) from [] (bus_add_driver+0xcc/0x1e4) > >>>>> [ 8.971832] [] (bus_add_driver) from [] (driver_register+0x9c/0xe0) > >>>>> [ 8.980255] [] (driver_register) from [] (do_one_initcall+0x100/0x1b8) > >>>>> [ 8.988983] [] (do_one_initcall) from [] (do_init_module+0x58/0x1c0) > >>>>> [ 8.997497] [] (do_init_module) from [] (SyS_init_module+0x54/0x64) > >>>>> [ 9.005950] [] (SyS_init_module) from [] (ret_fast_syscall+0x0/0x54) > >>>>> [ 9.015838] input: twl4030:vibrator as /devices/platform/68000000.ocp/48070000.i2c/i2c-0/0-0048/48070000.i2c:twl@48:audio/input/input2 > >>>>> > >>>>> node passed to of_find_node_by_name is put inside that function and new node > >>>>> is returned if found. Free returned node not already freed node. > >>>> > >>>> Hmm, if of_find_node_by_name() "puts" passed in node should we not "get" > >>>> it before calling of_find_node_by_name()? The node pointer in question > >>>> is simply copied from parent device. > >>> I'm not sure. what I can say is that I cannot see such error in 4.1 > >>> but only in 4.2-rcx. > >>> Adding Grant and Rob to CC, maybe they know what should be done and > >>> why I see such error in 4.2-rcx. > >> > >> The problem was that node passed into of_find_node_by_name is the the > >> starting point to search, but you should be doing the put on the > >> returned node. So the patch below is correct. > >> > >> As far as why in 4.2, it seems you have OF_DYNAMIC enabled in your > >> config either because you have DT unit test or overlays enabled. > >> Overlays are now user enable-able in 4.2. > > > > Right, but the question was whether we should also "get" the node that > > we are passing into of_find_node_by_name(), or, maybe better, stop > > of_find_node_by_name() from "putting" the node that is passed in? It is > > really surprising behavior. > > I agree that it is quite unexpected and would be much easier to understand > if it would not put the node. > > But I guess it is intended to be a convenience to make it easier to walk down > the tree, i.e. that you can simply write > > np = of_find_node_by_name(NULL, “level11”); > np = of_find_node_by_name(np, “level2”); > np = of_find_node_by_name(np, “level3”); Right, also for_each_node_by_name() relies on this behavior (but we can fix it to use something like __of_find_node_by_name_and_put_from()). > > Otherwise it would need some temporary variable and explicit calls to put the > parent level after finding a child node. > > On the other hand greping for of_find_node_by_name returns many more > calls with parent = NULL than others. So the put is ignored anyways. > > But it is a major change in semantics of a very low level function so it is > easy to introduce regressions (especially in out-of-the tree drivers). I am not sure how much we should care about out of tree drivers; but I worry that there are several callers that simply do: np = of_find_node_by_bame(dev->of_node, "blah"); in our tree... -- Dmitry -- 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/