linux-kernel - Re: [PATCH tip v5 2/5] kbuild: Add option to turn incompatible pointer check into error

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Message-ID: <565C9AE2.7040408@monom.org>
Date:	Mon, 30 Nov 2015 19:52:18 +0100
From:	Daniel Wagner <wagi@...om.org>
To:	paulmck@...ux.vnet.ibm.com,
	Daniel Wagner <daniel.wagner@...-carit.de>
Cc:	linux-kernel@...r.kernel.org, linux-rt-users@...r.kernel.org,
	Thomas Gleixner <tglx@...utronix.de>,
	Peter Zijlstra <peterz@...radead.org>,
	linux-kbuild@...r.kernel.org,
	Marcelo Tosatti <mtosatti@...hat.com>,
	Paolo Bonzini <pbonzini@...hat.com>,
	Paul Gortmaker <paul.gortmaker@...driver.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Boqun Feng <boqun.feng@...il.com>
Subject: Re: [PATCH tip v5 2/5] kbuild: Add option to turn incompatible
 pointer check into error

Hi Paul,

On 11/30/2015 06:38 PM, Paul E. McKenney wrote:
> On Mon, Nov 30, 2015 at 04:26:03PM +0100, Daniel Wagner wrote:
>> On 11/30/2015 02:38 PM, Daniel Wagner wrote:
>>> 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. Though for the beginning let's introduce it
>>> as options in the kernel hacking section.
>>
>> The kbuild bot found one problem for allmodconfig. I just send a fix for
>> it ("regmap: Fix leftover from struct reg_default to struct reg_sequence
>> change").
>
> This will result in an updated series, correct?

Not necessarily. This patch just points very verbose the incorrect 
pointer usage in regmap_register_path() users with allmodconfig. This 
series itself should be okay (unless I missed something).

cheers,
daniel
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