linux-kernel - Re: [PATCH] bus: vexpress-config: Add missing of_node

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Message-ID: <20160125121720.GC1194@e106497-lin.cambridge.arm.com>
Date:	Mon, 25 Jan 2016 12:17:20 +0000
From:	liviu.dudau@....com
To:	Amitoj Kaur Chawla <amitoj1606@...il.com>
Cc:	sudeep.holla@....com, lorenzo.pieralisi@....com,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	julia.lawall@...6.fr
Subject: Re: [PATCH] bus: vexpress-config: Add missing of_node_put

On Fri, Jan 22, 2016 at 11:38:38PM +0530, Amitoj Kaur Chawla wrote:
> for_each_compatible_node performs an of_node_get on each iteration, so
> to break out of the loop an of_node_put is required.
> 
> Found using Coccinelle. The semantic patch used for this is as follows:
> 
> // <smpl>
> @@
> expression e;
> local idexpression n;
> @@
> 
>  for_each_compatible_node(n, ...) {
>    ... when != of_node_put(n)
>        when != e = n
> (
>    return n;
> +  of_node_put(n);
> ?  return ...;
> )
>    ...
>  }
> // </smpl>
> 
> Signed-off-by: Amitoj Kaur Chawla <amitoj1606@...il.com>

Hi Amitoj,

> ---
>  drivers/bus/vexpress-config.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/bus/vexpress-config.c b/drivers/bus/vexpress-config.c
> index 6575c0f..c3cb76b 100644
> --- a/drivers/bus/vexpress-config.c
> +++ b/drivers/bus/vexpress-config.c
> @@ -192,8 +192,10 @@ static int __init vexpress_config_init(void)
>  	/* Need the config devices early, before the "normal" devices... */
>  	for_each_compatible_node(node, NULL, "arm,vexpress,config-bus") {
>  		err = vexpress_config_populate(node);
> -		if (err)
> +		if (err) {
> +			of_node_put(node);
>  			break;
> +		}

This automatically generated patch only solves half of the problem (for the error
path).

>  	}
>  
>  	return err;
> -- 
> 1.9.1
> 

I feel that a better patch would be the following, where the node is released
regardless of the result of vexpress_config_populate().

--8<--------------------------------------------------------------------------
diff --git a/drivers/bus/vexpress-config.c b/drivers/bus/vexpress-config.c
index 6575c0f..c57453d 100644
--- a/drivers/bus/vexpress-config.c
+++ b/drivers/bus/vexpress-config.c
@@ -192,6 +192,7 @@ static int __init vexpress_config_init(void)
 	/* Need the config devices early, before the "normal" devices... */
 	for_each_compatible_node(node, NULL, "arm,vexpress,config-bus") {
 		err = vexpress_config_populate(node);
+		of_node_put(node);
 		if (err)
 			break;
 	}
-->8--------------------------------------------------------------------------

Best regards,
Liviu

-- 
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