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

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Message-ID: <20151130173842.GV26643@linux.vnet.ibm.com>
Date:	Mon, 30 Nov 2015 09:38:42 -0800
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	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

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?

							Thanx, Paul

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