linux-kernel - Re: [PATCH v1 1/1] platform/x86: ideapad-laptop: Make the scope

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Message-ID: <8d35db80-5bf3-40ca-b041-8a94e76739c7@redhat.com>
Date: Thu, 5 Sep 2024 10:33:22 +0200
From: Hans de Goede <hdegoede@...hat.com>
To: Andy Shevchenko <andy.shevchenko@...il.com>
Cc: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
 Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>,
 Gergo Koteles <soyer@....hu>, platform-driver-x86@...r.kernel.org,
 linux-kernel@...r.kernel.org, Ike Panhc <ike.pan@...onical.com>,
 Peter Zijlstra <peterz@...radead.org>, Josh Poimboeuf <jpoimboe@...nel.org>,
 Nathan Chancellor <nathan@...nel.org>, kernel test robot <lkp@...el.com>
Subject: Re: [PATCH v1 1/1] platform/x86: ideapad-laptop: Make the
 scope_guard() clear of its scope

Hi Andy,

On 9/4/24 10:18 PM, Andy Shevchenko wrote:
> Wed, Sep 04, 2024 at 08:14:53PM +0200, Hans de Goede kirjoitti:
>> Hi,
>>
>> On 8/29/24 6:50 PM, Andy Shevchenko wrote:
>>> First of all, it's a bit counterintuitive to have something like
>>>
>>> 	int err;
>>> 	...
>>> 	scoped_guard(...)
>>> 		err = foo(...);
>>> 	if (err)
>>> 		return err;
>>>
>>> Second, with a particular kernel configuration and compiler version in
>>> one of such cases the objtool is not happy:
>>>
>>>   ideapad-laptop.o: warning: objtool: .text.fan_mode_show: unexpected end of section
>>>
>>> I'm not an expert on all this, but the theory is that compiler and
>>> linker in this case can't understand that 'result' variable will be
>>> always initialized as long as no error has been returned. Assigning
>>> 'result' to a dummy value helps with this. Note, that fixing the
>>> scoped_guard() scope (as per above) does not make issue gone.
>>>
>>> That said, assign dummy value and make the scope_guard() clear of its scope.
>>> For the sake of consistency do it in the entire file.
>>>
>>> Fixes: 7cc06e729460 ("platform/x86: ideapad-laptop: add a mutex to synchronize VPC commands")
>>> Reported-by: kernel test robot <lkp@...el.com>
>>> Closes: https://lore.kernel.org/oe-kbuild-all/202408290219.BrPO8twi-lkp@intel.com/
>>> Signed-off-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
> 
>> Thank you for your patch, I've applied this patch to my review-hans 
>> branch:
>> https://git.kernel.org/pub/scm/linux/kernel/git/pdx86/platform-drivers-x86.git/log/?h=review-hans
> 
> Have you had a chance to go through the discussion?

Yes I did read the entire discussion.

> TL;DR: please defer this. There is still no clear understanding of the root
> cause and the culprit.

My gist from the discussion was that this was good to have regardless of
the root cause.

IMHO the old construction where the scoped-guard only guards the function-call
and not the "if (ret)" on the return value of the guarded call was quite ugly /
convoluted / hard to read and this patch is an improvement regardless.

Regards,

Hans