[PATCH v3] devres: Refactor using guards

[Andrea Calabrese]

Hi Greg,

On 12/06/2024 12:05, Greg KH wrote:
> On Wed, Jun 12, 2024 at 12:00:06PM +0200, Andrea Calabrese wrote:
>> Hi Lucas,
>>
>> On 12/06/2024 11:26, Lucas Stach wrote:
>>> Am Dienstag, dem 11.06.2024 um 11:37 +0200 schrieb Andrea Calabrese:
>>>> Code refactoring using the recent guard and scoped_guard macros
>>>> for automatic cleanup of the spinlocks. This does not change the
>>>> effective behaviour of the kernel, but guarantees a cleaned-up exit from
>>>> each lock, automatically avoiding potential deadlocks.
>>>>
>>>> Signed-off-by: Andrea Calabrese <andrea.calabrese at amarulasolutions.com>
>>>>
>>>> ---
>>>> Changed commit message from V2. Also changed title, shortened the file
>>>> name.
>>>>
>>>> diff --git a/drivers/base/devres.c b/drivers/base/devres.c
>>>> index 3df0025d12aa..a98720e0cb2b 100644
>>>> --- a/drivers/base/devres.c
>>>> +++ b/drivers/base/devres.c
>>>> @@ -194,14 +194,12 @@ void devres_for_each_res(struct device *dev, dr_release_t release,
>>>>    {
>>>>    	struct devres_node *node;
>>>>    	struct devres_node *tmp;
>>>> -	unsigned long flags;
>>>>    	if (!fn)
>>>>    		return;
>>>> -	spin_lock_irqsave(&dev->devres_lock, flags);
>>>> -	list_for_each_entry_safe_reverse(node, tmp,
>>>> -			&dev->devres_head, entry) {
>>>> +	guard(spinlock)(&dev->devres_lock);
>>> This is not equivalent to the current code. You are dropping the
>>> _irqsave part of the locking scheme, totally changing the semantics
>>> here. This issue is present in multiple places in this patch.
>>>
>>> Regards,
>>> Lucas
>> I don't see where is the issue here, as I am using both guard and
>> scoped_guard similarly to how they are used in drivers/gpio/gpiolib-cdev.c,
>> which I took as a reference for the usage of the construct. If so, probably
>> we may  both be using it wrong.
> Look at the difference between calling:
> 	spin_lock(&lock);
> and
> 	spin_lock_irqsave(&lock, flags);
>
> They are functionally NOT the same.
>
> thanks,
>
> greg k-h

Ouch, I saw it now... I will fix it and send a V4.

Thank you!

Andrea