linux-kernel - Re:Re: [PATCH v2] arch: powerpc: platforms: 85xx: Add missing of_node_put in sgy

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Date:   Fri, 17 Jun 2022 10:25:13 +0800 (CST)
From:   "Liang He" <windhl@....com>
To:     "Michael Ellerman" <mpe@...erman.id.au>
Cc:     "Christophe JAILLET" <christophe.jaillet@...adoo.fr>,
        oss@...error.net, paulus@...ba.org, christophe.leroy@...roup.eu,
        nixiaoming@...wei.com, linuxppc-dev@...ts.ozlabs.org,
        linux-kernel@...r.kernel.org
Subject: Re:Re: [PATCH v2] arch: powerpc: platforms: 85xx: Add missing
 of_node_put in sgy_cts1000.c




At 2022-06-17 07:37:06, "Michael Ellerman" <mpe@...erman.id.au> wrote:
>Christophe JAILLET <christophe.jaillet@...adoo.fr> writes:
>> Le 16/06/2022 à 17:19, Liang He a écrit :
>>> In gpio_halt_probe(), of_find_matching_node() will return a node pointer with
>>> refcount incremented. We should use of_node_put() in each fail path or when it
>>> is not used anymore.
>>> 
>>> Signed-off-by: Liang He <windhl@....com>
>>> ---
>>>   changelog:
>>> 
>>>   v2: use goto-label patch style advised by Christophe.
>>>   v1: add of_node_put() before each exit.
>>> 
>>>   arch/powerpc/platforms/85xx/sgy_cts1000.c | 27 +++++++++++++++--------
>>>   1 file changed, 18 insertions(+), 9 deletions(-)
>>> 
>>> diff --git a/arch/powerpc/platforms/85xx/sgy_cts1000.c b/arch/powerpc/platforms/85xx/sgy_cts1000.c
>>> index 98ae64075193..e280f963d88c 100644
>>> --- a/arch/powerpc/platforms/85xx/sgy_cts1000.c
>>> +++ b/arch/powerpc/platforms/85xx/sgy_cts1000.c
>>> @@ -73,6 +73,7 @@ static int gpio_halt_probe(struct platform_device *pdev)
>...
>>> @@ -122,8 +127,12 @@ static int gpio_halt_probe(struct platform_device *pdev)
>>>   
>>>   	printk(KERN_INFO "gpio-halt: registered GPIO %d (%d trigger, %d"
>>>   	       " irq).\n", gpio, trigger, irq);
>>> +	ret = 0;
>>>   
>>> -	return 0;
>>> +err_put:
>>> +	of_node_put(halt_node);
>>> +	halt_node = NULL;
>>
>> Hi,
>> so now we set 'halt_node' to NULL even in the normal case.
>> This is really spurious.
>>
>> Look at gpio_halt_cb(), but I think that this is just wrong and badly 
>> breaks this driver.
>
>I agree, thanks for reviewing.
>
>I think the cleanest solution is to use a local variable for the node in
>the body of gpio_halt_probe(), and only assign to halt_node once all the
>checks have passed.
>
>So something like:
>
>        struct device_node *child_node;
>
>	child_node = of_find_matching_node(node, child_match);
>        ...
>
>	printk(KERN_INFO "gpio-halt: registered GPIO %d (%d trigger, %d"
>	       " irq).\n", gpio, trigger, irq);
>        ret = 0;
>        halt_node = of_node_get(child_node);
>
>out_put:
>        of_node_put(child_node);
>        
>	return ret;
>}
>
>
>cheers

Hi, Michael and Christophe,

I am writing the new patch based on Michael's advice. However, I wonder if there is
any place to call of_node_put(halt_node)?  As I do not exactly know if gpio_halt_remove()
or anyother place can correctly release this global reference？
If not, it is correct that I add a of_node_put(halt_node) in gpio_halt_remove(), right?

Thanks and wait for your replies.

Liang