Messages in this thread | | | Date | Sun, 15 Apr 2012 02:48:27 +0530 | From | "Srivatsa S. Bhat" <> | Subject | Re: [RFC 0/3] Extend type checking macros |
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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
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