linux-kernel - Re: [RFC PATCH] cleanup: make scoped

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Message-ID: <bb531337-b155-40d2-96e3-8ece7ea2d927@intel.com>
Date: Fri, 27 Sep 2024 16:08:30 +0200
From: Przemek Kitszel <przemyslaw.kitszel@...el.com>
To: Dan Carpenter <dan.carpenter@...aro.org>
CC: <linux-kernel@...r.kernel.org>, Peter Zijlstra <peterz@...radead.org>,
	<amadeuszx.slawinski@...ux.intel.com>, Tony Nguyen
	<anthony.l.nguyen@...el.com>, <nex.sw.ncis.osdt.itp.upstreaming@...el.com>,
	<netdev@...r.kernel.org>, Andy Shevchenko <andriy.shevchenko@...el.com>
Subject: Re: [RFC PATCH] cleanup: make scoped_guard() to be return-friendly

On 9/27/24 09:31, Dan Carpenter wrote:
> On Thu, Sep 26, 2024 at 03:41:38PM +0200, Przemek Kitszel wrote:
>> diff --git a/include/linux/cleanup.h b/include/linux/cleanup.h
>> index d9e613803df1..6b568a8a7f9c 100644
>> --- a/include/linux/cleanup.h
>> +++ b/include/linux/cleanup.h
>> @@ -168,9 +168,16 @@ static inline class_##_name##_t class_##_name##ext##_constructor(_init_args) \
>>   
>>   #define __guard_ptr(_name) class_##_name##_lock_ptr
>>   
>> -#define scoped_guard(_name, args...)					\
>> -	for (CLASS(_name, scope)(args),					\
>> -	     *done = NULL; __guard_ptr(_name)(&scope) && !done; done = (void *)1)
>> +#define scoped_guard(_name, args...)	\
>> +	__scoped_guard_labeled(__UNIQUE_ID(label), _name, args)
>> +
>> +#define __scoped_guard_labeled(_label, _name, args...)	\
>> +	if (0)						\
>> +		_label: ;				\
>> +	else						\
>> +		for (CLASS(_name, scope)(args);		\
>> +		     __guard_ptr(_name)(&scope), 1;	\
>                                                 ^^^
>> +		     ({ goto _label; }))
>>   
> 
> Remove the ", 1".  The point of the __guard_ptr() condition is for try_locks
> but the ", 1" means they always succeed.  The only try lock I can find in

You are right that the __guard_ptr() is conditional for the benefit of
try_locks. But here we have unconditional lock. And removing ", 1" part
makes compiler complaining with the very same message:
error: control reaches end of non-void function [-Werror=return-type]

so ", 1" part is on purpose and must stay there to aid compiler.

> the current tree is tsc200x_esd_work().
> 
> regards,
> dan carpenter
> 
>