Re:Re: [PATCH] arch: x86: kernel: Add missing of_node_put() in devicetree.c

[和亮]

Hi, rob, thanks for your reply.

The of_find_xx will increase the refcounter for the local reference, so when 
the function return, we need a decrease for the destroy of the local reference.
The device will not be freed as its refcounter will be sure larger than 0 when 
the function returns.

All we need is to keep the refcounting balance, right?




At 2022-06-16 00:26:16, "Rob Herring" <robh@xxxxxxxxxx> wrote:
>On Wed, Jun 15, 2022 at 9:03 AM Liang He <windhl@xxxxxxx> wrote:
>>
>> In dtb_setup_hpet(), of_find_compatible_node() will return a node
>> pointer with refcount incremented. We should use of_node_put() when it
>> is not used anymore.
>>
>> Signed-off-by: Liang He <windhl@xxxxxxx>
>> ---
>>  arch/x86/kernel/devicetree.c | 3 +++
>>  1 file changed, 3 insertions(+)
>>
>> diff --git a/arch/x86/kernel/devicetree.c b/arch/x86/kernel/devicetree.c
>> index 5cd51f25f446..6a386424ddf7 100644
>> --- a/arch/x86/kernel/devicetree.c
>> +++ b/arch/x86/kernel/devicetree.c
>> @@ -120,6 +120,9 @@ static void __init dtb_setup_hpet(void)
>>         if (!dn)
>>                 return;
>>         ret = of_address_to_resource(dn, 0, &r);
>> +
>> +       of_node_put(dn);
>> +
>
>You don't want a put on success. If you are using the device, then you
>want to hold a reference to it.
>
>I would guess that if you have an error here and don't have your
>timer, you're not going to finish booting anyways.
>
>Finally, wouldn't dtb_lapic_setup() and dtb_add_ioapic() also need a
>similar change? But again, if those aren't initialized, you probably
>aren't getting very far.
>
>
>>         if (ret) {
>>                 WARN_ON(1);
>>                 return;
>> --
>> 2.25.1
>>