linux-kernel - [RFC 0/3] Extend type checking macros

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Date:	Sat, 14 Apr 2012 18:14:42 -0400
From:	Sasha Levin <levinsasha928@...il.com>
To:	torvalds@...ux-foundation.org, akpm@...ux-foundation.org,
	peterz@...radead.org, mingo@...e.hu, hpa@...or.com,
	tglx@...utronix.de, srivatsa.bhat@...ux.vnet.ibm.com
Cc:	linux-kernel@...r.kernel.org, Sasha Levin <levinsasha928@...il.com>
Subject: [RFC 0/3] Extend type checking macros

Commit e3831ed ("sched: Fix incorrect usage of for_each_cpu_mask() in
select_fallback_rq()") fixes a very non obvious bug in select_fallback_rq()
which was caused by passing 'struct cpumask' instead of 'struct cpumask *'
to a macro in include/linux/cpumask.h

This bug was quite a pain to debug since it doesn't raise any warnings or
erros during compilation, and the assumption of the kernel hackers who try
to fix a bug is that if the compiler didn't complain, they passed the right
types to functions.

This series of patches adds some more type checking macros to the forgotten
include/linux/typecheck.h, it modified for_each_cpu_mask() to use those
macros to trigger a warning when needed (this is a nice demonstration of how
the bug mentioned before would have been visible with these checks), and
modifies min()/max() and friend to use these macros as well to show their
value in reducing duplicate code and improving readability.

Sasha Levin (3):
  typecheck: extend typecheck.h with more useful typechecking macros
  sched: add type checks to for_each_cpu_mask()
  kernel.h: use new typechecking macros in min()/max() and friends

 include/linux/cpumask.h   |    4 ++-
 include/linux/kernel.h    |   47 ++++++++++++++------------------------------
 include/linux/typecheck.h |   42 ++++++++++++++++++++++++++++++++-------
 3 files changed, 52 insertions(+), 41 deletions(-)

-- 
1.7.8.5

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