linux-kernel - Re: [PATCH] kbuild: Add option to turn incompatible pointer check into error

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Message-ID: <56E88003.3050708@suse.com>
Date:	Tue, 15 Mar 2016 22:34:59 +0100
From:	Michal Marek <mmarek@...e.com>
To:	Ingo Molnar <mingo@...nel.org>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Daniel Wagner <wagi@...om.org>, linux-kbuild@...r.kernel.org,
	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...hat.com>,
	Daniel Wagner <daniel.wagner@...-carit.de>
Subject: Re: [PATCH] kbuild: Add option to turn incompatible pointer check
 into error

Dne 8.3.2016 v 10:19 Ingo Molnar napsal(a):
> 
> * Thomas Gleixner <tglx@...utronix.de> wrote:
> 
>> On Tue, 8 Mar 2016, Daniel Wagner wrote:
>>
>>> From: Daniel Wagner <daniel.wagner@...-carit.de>
>>>
>>> With the introduction of the simple wait API we have two very
>>> similar APIs in the kernel. For example wake_up() and swake_up()
>>> is only one character away. Although the compiler will warn
>>> happily the wrong usage it keeps on going an even links the kernel.
>>> Thomas and Peter would rather like to see early missuses reported
>>> as error early on.
>>>
>>> In a first attempt we tried to wrap all swait and wait calls
>>> into a macro which has an compile time type assertion. The result
>>> was pretty ugly and wasn't able to catch all wrong usages.
>>> woken_wake_function(), autoremove_wake_function() and wake_bit_function()
>>> are assigned as function pointers. Wrapping them with a macro around is
>>> not possible. Prefixing them with '_' was also not a real option
>>> because there some users in the kernel which do use them as well.
>>> All in all this attempt looked to intrusive and too ugly.
>>>
>>> An alternative is to turn the pointer type check into an error which
>>> catches wrong type uses. Obviously not only the swait/wait ones. That
>>> isn't a bad thing either.
>>>
>>> Signed-off-by: Daniel Wagner <daniel.wagner@...-carit.de>
>>> Acked-by: Peter Zijlstra (Intel) <peterz@...radead.org>
>>> Cc: Thomas Gleixner <tglx@...utronix.de>
>>
>> Acked-by: Thomas Gleixner <tglx@...utronix.de>

Applied to kbuild.git#kbuild.

> 
> Note that there will be a few build failures triggered by this, for example this 
> fix from linux-next is needed:
> 
>> commit db9b60400f9253c25ae639797df2d0ff7a35d9d8
>> Author: Sudip Mukherjee <sudipm.mukherjee@...il.com>
>> Date:   Tue Feb 2 11:35:55 2016 +0530
>>
>>     drm/gma500: remove helper function

OK. I will send a pull request to Linus only after at least
x86_64/allyescofnig is fixed.

Michal