Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753589AbbG2Ruf (ORCPT ); Wed, 29 Jul 2015 13:50:35 -0400 Received: from mo4-p00-ob.smtp.rzone.de ([81.169.146.219]:25463 "EHLO mo4-p00-ob.smtp.rzone.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752616AbbG2Rue convert rfc822-to-8bit (ORCPT ); Wed, 29 Jul 2015 13:50:34 -0400 X-RZG-AUTH: :JGIXVUS7cutRB/49FwqZ7WcKdUCnXG6JabOfSXKWrat+jdPvyeGM X-RZG-CLASS-ID: mo00 Content-Type: text/plain; charset=windows-1252 Mime-Version: 1.0 (Mac OS X Mail 7.3 \(1878.6\)) Subject: Re: [PATCH] input: twl4030-vibra: Fix ERROR: Bad of_node_put() warning From: "Dr. H. Nikolaus Schaller" In-Reply-To: <20150729172602.GB23178@dtor-ws> Date: Wed, 29 Jul 2015 19:50:24 +0200 Cc: Rob Herring , Belisko Marek , "linux-input@vger.kernel.org" , LKML , Rob Herring , Grant Likely Content-Transfer-Encoding: 8BIT Message-Id: References: <1437683914-4660-1-git-send-email-marek@goldelico.com> <20150723205314.GB12733@dtor-ws>

<20150729172602.GB23178@dtor-ws> To: Dmitry Torokhov X-Mailer: Apple Mail (2.1878.6) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4548 Lines: 82 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?); 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). Just my 2 cts, Nikolaus -- 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/