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Date: Sun, 15 Apr 2012 02:48:27 +0530 From: "Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com> To: Sasha Levin <levinsasha928@...il.com> CC: torvalds@...ux-foundation.org, akpm@...ux-foundation.org, peterz@...radead.org, mingo@...e.hu, hpa@...or.com, tglx@...utronix.de, linux-kernel@...r.kernel.org Subject: Re: [RFC 0/3] Extend type checking macros On 04/15/2012 03:44 AM, Sasha Levin wrote: > 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 > Good heavens! I just found out that *each* *and* *every* *one* of the existing 12 users of for_each_cpu_mask() are wrong!! Unbelievable! > 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() I think it would be better to correct and move the existing 12 users of for_each_cpu_mask() to for_each_cpu() and simply get rid of the obsolete for_each_cpu_mask() macro. After all, why do we need 2 macros that do the exact same thing? > 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(-) > Regards, Srivatsa S. Bhat -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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