Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
        id S1751397AbdGQNrr (ORCPT <rfc822;w@1wt.eu>);
        Mon, 17 Jul 2017 09:47:47 -0400
Received: from hqemgate16.nvidia.com ([216.228.121.65]:18278 "EHLO
        hqemgate16.nvidia.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
        with ESMTP id S1751306AbdGQNro (ORCPT
        <rfc822;linux-kernel@vger.kernel.org>);
        Mon, 17 Jul 2017 09:47:44 -0400
X-PGP-Universal: processed;
        by hqpgpgate101.nvidia.com on Mon, 17 Jul 2017 06:47:44 -0700
Subject: Re: [PATCH] thermal: tegra: delete unneeded of_node_put
To: Julia Lawall <Julia.Lawall@lip6.fr>, Zhang Rui <rui.zhang@intel.com>
CC: <kernel-janitors@vger.kernel.org>,
        Eduardo Valentin <edubezval@gmail.com>,
        Thierry Reding <thierry.reding@gmail.com>, <linux-pm@vger.kernel.org>,
        <linux-tegra@vger.kernel.org>, <linux-kernel@vger.kernel.org>
References: <1500108152-1812-1-git-send-email-Julia.Lawall@lip6.fr>
From: Jon Hunter <jonathanh@nvidia.com>
Message-ID: <66e7906c-9472-4fcb-7c04-750bb27d3989@nvidia.com>
Date: Mon, 17 Jul 2017 14:47:14 +0100
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101
 Thunderbird/52.2.1
MIME-Version: 1.0
In-Reply-To: <1500108152-1812-1-git-send-email-Julia.Lawall@lip6.fr>
X-Originating-IP: [10.26.11.200]
X-ClientProxiedBy: UKMAIL102.nvidia.com (10.26.138.15) To UKMAIL101.nvidia.com
 (10.26.138.13)
Content-Type: text/plain; charset="utf-8"
Content-Language: en-US
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org
Content-Length: 2544
Lines: 74


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.

Cheers
Jon

-- 
nvpublic