Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
        id S1752229AbdLEGRG (ORCPT <rfc822;w@1wt.eu>);
        Tue, 5 Dec 2017 01:17:06 -0500
Received: from mail3-relais-sop.national.inria.fr ([192.134.164.104]:32823
        "EHLO mail3-relais-sop.national.inria.fr" rhost-flags-OK-OK-OK-OK)
        by vger.kernel.org with ESMTP id S1750740AbdLEGRF (ORCPT
        <rfc822;linux-kernel@vger.kernel.org>);
        Tue, 5 Dec 2017 01:17:05 -0500
X-IronPort-AV: E=Sophos;i="5.45,363,1508796000"; 
   d="scan'208";a="247193785"
Date: Tue, 5 Dec 2017 07:17:02 +0100 (CET)
From: Julia Lawall <julia.lawall@lip6.fr>
X-X-Sender: jll@hadrien
To: Eduardo Valentin <edubezval@gmail.com>
cc: Jon Hunter <jonathanh@nvidia.com>, Zhang Rui <rui.zhang@intel.com>,
        kernel-janitors@vger.kernel.org,
        Thierry Reding <thierry.reding@gmail.com>, linux-pm@vger.kernel.org,
        linux-tegra@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] thermal: tegra: delete unneeded of_node_put
In-Reply-To: <20171205014918.GB3536@localhost.localdomain>
Message-ID: <alpine.DEB.2.20.1712050716210.2555@hadrien>
References: <1500108152-1812-1-git-send-email-Julia.Lawall@lip6.fr> <66e7906c-9472-4fcb-7c04-750bb27d3989@nvidia.com> <alpine.DEB.2.20.1707171641190.2038@hadrien> <20171205014918.GB3536@localhost.localdomain>
User-Agent: Alpine 2.20 (DEB 67 2015-01-07)
MIME-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org
Content-Length: 3509
Lines: 89



On Mon, 4 Dec 2017, Eduardo Valentin wrote:

> On Mon, Jul 17, 2017 at 04:42:38PM +0200, Julia Lawall wrote:
> >
> >
> > On Mon, 17 Jul 2017, Jon Hunter wrote:
> >
> > >
> > > On 15/07/17 09:42, Julia Lawall wrote:
> > > > Device node iterators perform an of_node_put on each iteration, so putting
> > > > an of_node_put before a continue results in a double put.
> > > >
> > > > The semantic match that finds this problem is as follows
> > > > (http://coccinelle.lip6.fr):
> > > >
> > > > // <smpl>
> > > > @@
> > > > expression e1;
> > > > local idexpression child;
> > > > iterator name for_each_child_of_node;
> > > > @@
> > > >
> > > >  for_each_child_of_node(e1,child) {
> > > >    ... when != of_node_get(child)
> > > > *  of_node_put(child);
> > > >    ...
> > > > *  continue;
> > > > }
> > > > // </smpl>
> > > >
> > > > Furthermore, the call to thermal_of_cooling_device_register immediately
> > > > calls __thermal_cooling_device_register with the same arguments.  The
> > > > latter function stores the device node argument, which is the second
> > > > argument of for_each_child_of_node, in the returned thermal_cooling_device
> > > > structure.  This returned structure is then stored in the cdev field of
> > > > stc.  Thus it seems that the second argument of for_each_child_of_node
> > > > escapes the scope of the for_each_child_of_node, so an explicit of_node_get
> > > > on success of thermal_of_cooling_device_register is also needed.
> > > >
> > > > Signed-off-by: Julia Lawall <Julia.Lawall@lip6.fr>
> > > >
> > > > ---
> > > >  drivers/thermal/tegra/soctherm.c |    2 +-
> > > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > > >
> > > > diff --git a/drivers/thermal/tegra/soctherm.c b/drivers/thermal/tegra/soctherm.c
> > > > index 7d2db23..10f4fdd 100644
> > > > --- a/drivers/thermal/tegra/soctherm.c
> > > > +++ b/drivers/thermal/tegra/soctherm.c
> > > > @@ -1014,7 +1014,6 @@ static void soctherm_init_hw_throt_cdev(struct platform_device *pdev)
> > > >  		tcd = thermal_of_cooling_device_register(np_stcc,
> > > >  							 (char *)name, ts,
> > > >  							 &throt_cooling_ops);
> > > > -		of_node_put(np_stcc);
> > > >  		if (IS_ERR_OR_NULL(tcd)) {
> > > >  			dev_err(dev,
> > > >  				"throttle-cfg: %s: failed to register cooling device\n",
> > > > @@ -1022,6 +1021,7 @@ static void soctherm_init_hw_throt_cdev(struct platform_device *pdev)
> > > >  			continue;
> > > >  		}
> > > >
> > > > +		of_node_get(np_stcc);
> > > >  		stc->cdev = tcd;
> > > >  		stc->init = true;
> > > >  	}
> > >
> > > Thanks for fixing this. However, I am wondering if it is better for the
> > > 'of_node_get' to be placed within the
> > > thermal_of_cooling_device_register() function as it seems a bit odd if
> > > the caller needs to know that this is being stored for later use.
> > >
> > > Also, taking a quick look, I see a couple other drivers calling
> > > thermal_of_cooling_device_register() and they are also not calling
> > > of_node_get on success. So it maybe easier to fix placing it in the
> > > thermal_of_cooling_device_register() function.
> >
> > I'm not an expert, but I had the impression that from some call sites, the
> > get would have been done already, because the argument is already stored
> > in some structure.  I can check more exhaustively.
>
> Julia, I agree with Jon here. Better if fixed in the API itself. Are you
> still planning on sending a fix for this?

This has fallen off my stack, and I'mnot sure that Ican get to it in the
short term.

julia