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

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Date:	Mon, 30 Nov 2015 16:26:03 +0100
From:	Daniel Wagner <daniel.wagner@...-carit.de>
To:	<linux-kernel@...r.kernel.org>, <linux-rt-users@...r.kernel.org>
CC:	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 E. McKenney" <paulmck@...ux.vnet.ibm.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

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").
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