linux-kernel - Re: [PATCH] rtc: avoid calling platform_device_put() twice in test

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Date:	Tue, 6 Nov 2012 16:51:44 -0800
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Wei Yongjun <weiyj.lk@...il.com>
Cc:	a.zummo@...ertech.it, yongjun_wei@...ndmicro.com.cn,
	rtc-linux@...glegroups.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] rtc: avoid calling platform_device_put() twice in
 test_init()

On Tue, 23 Oct 2012 13:08:41 +0800
Wei Yongjun <weiyj.lk@...il.com> wrote:

> From: Wei Yongjun <yongjun_wei@...ndmicro.com.cn>
> 
> In case of error, the function test_init() need to call
> platform_device_del() instead of platform_device_unregister().
> Otherwise, we may call platform_device_put() twice.
> 
> dpatch engine is used to auto generate this patch.
> (https://github.com/weiyj/dpatch)
> 
> Signed-off-by: Wei Yongjun <yongjun_wei@...ndmicro.com.cn>
> ---
>  drivers/rtc/rtc-test.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/rtc/rtc-test.c b/drivers/rtc/rtc-test.c
> index 7e96254..209a127 100644
> --- a/drivers/rtc/rtc-test.c
> +++ b/drivers/rtc/rtc-test.c
> @@ -164,7 +164,7 @@ static int __init test_init(void)
>  	return 0;
>  
>  exit_device_unregister:
> -	platform_device_unregister(test0);
> +	platform_device_del(test0);
>  
>  exit_free_test1:
>  	platform_device_put(test1);

Is platform_device_del() the partner to platform_device_add()?  If so
then yes, this looks right.  But I think the labels can be improved:

--- a/drivers/rtc/rtc-test.c~rtc-avoid-calling-platform_device_put-twice-in-test_init-fix
+++ a/drivers/rtc/rtc-test.c
@@ -152,24 +152,24 @@ static int __init test_init(void)
 
 	if ((test1 = platform_device_alloc("rtc-test", 1)) == NULL) {
 		err = -ENOMEM;
-		goto exit_free_test0;
+		goto exit_put_test0;
 	}
 
 	if ((err = platform_device_add(test0)))
-		goto exit_free_test1;
+		goto exit_put_test1;
 
 	if ((err = platform_device_add(test1)))
-		goto exit_device_unregister;
+		goto exit_del_test0;
 
 	return 0;
 
-exit_device_unregister:
+exit_del_test0:
 	platform_device_del(test0);
 
-exit_free_test1:
+exit_put_test1:
 	platform_device_put(test1);
 
-exit_free_test0:
+exit_put_test0:
 	platform_device_put(test0);
 
 exit_driver_unregister:
_


However, take a look at test_exit().  it does
platform_device_unregister(test0) when test0 is in the same state.  Is
that code wrong as well?  Presumably it's working OK?

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