linux-kernel - Re: [PATCH] clocksource/drivers/tango-xtal: Fix incorrect test

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Date:	Tue, 19 Apr 2016 20:22:56 +0200
From:	Mason <slash.tmp@...e.fr>
To:	Daniel Lezcano <daniel.lezcano@...aro.org>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Sebastian Frias <sf84@...oste.net>,
	Mans Rullgard <mans@...sr.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] clocksource/drivers/tango-xtal: Fix incorrect test

On 19/04/2016 19:31, Daniel Lezcano wrote:
> On Tue, Apr 19, 2016 at 07:21:20PM +0200, Mason wrote:
>> On 19/04/2016 16:59, Daniel Lezcano wrote:
>>> On Tue, Apr 19, 2016 at 04:05:19PM +0200, Mason wrote:
>>>> On 19/04/2016 15:13, Daniel Lezcano wrote:
>>>>
>>>>> On Tue, Apr 19, 2016 at 02:15:15PM +0200, Mason wrote:
>>>>>
>>>>>> From: Marc Gonzalez <marc_gonzalez@...madesigns.com>
>>>>>>
>>>>>> Commit 0881841f7e78 changed "if (ret != 0)" to "if (!ret)"
>>>>>>
>>>>>> Fixes: 0881841f7e78 ("Replace code by clocksource_mmio_init")
>>>>>> Signed-off-by: Marc Gonzalez <marc_gonzalez@...madesigns.com>
>>>>>> ---
>>>>>
>>>>> Please resend the patch with the fix only, without s/ret/err/
>>>>
>>>> As I wrote on IRC, I think it is misguided to consider variable
>>>> renaming as not part of the fix. A properly named variable helps
>>>> reviewers by communicating intent.
>>>>
>>>> Had I named the variable 'err' in the first place, would you have
>>>> introduced the bug by writing
>>>>
>>>>   if (!err) {
>>>>     pr_err("registration failed");
>>>>   }
>>>>
>>>> or would if (!err) have jumped out for an error path?
>>>> (Not a rhetorical question; if you say it would not have helped,
>>>> then I guess my mental workflow is different.)
>>>
>>> Ok I won't argue for a stupid variable name.
>>>
>>> The point is we are at v4.6-rc4 and even if the change is obvious, it is a 
>>> good practice to do a simple change:
>>>
>>> -       if (!ret) {
>>> +       if (ret) {
>>>
>>> Why ? Because maintainers have a lot of code to review, and removing the 
>>> noise as much as possible helps them to make their life easier especially 
>>> when they have to pay double attention for fixes at RC.
>>>
>>> If the 'ret' name is a problem for you, just send another patch for v4.7 to 
>>> change the name.
>>
>> I want to be sure I understand, please correct me if I'm wrong.
>>
>> 1) you have already committed the minimal fix above (changing only
>> the test, and keeping the original variable name) and this will be
>> pushed to linux-next for the upcoming v4.6-rc
> 
> yes.

Thanks for the quick turn around.

>> 2) if I want to change the variable name, I can send another patch,
>> to be pushed in the next merge window, for v4.7
> 
> yes.
> 
>> Do you agree that 2) would be a (minor) improvement?
>> If not, I will not bother with the patch.
> 
> Usually people are using 'ret'
> 
> grep -r "ret =" drivers/ | wc -l
> 76754
> 
> or are using 'err'
> 
> grep -r "err =" drivers/ | wc -l
> 27940
> 
> Up to you ...

About the error handling... you advised against panic()
because there might be other clock sources.

Does it makes sense to give up registering sched_clock
and delay_timer when the clocksource registration fails?

Regards.