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    SubjectRe: [Bug #11342] Linux 2.6.27-rc3: kernel BUG at mm/vmalloc.c - bisected

    On Tue, 26 Aug 2008, Yinghai Lu wrote:
    > wonder if could use "unsigned long *" directly.

    I would actually suggest something like this:

    - we continue to have a magic "cpumask_t".

    - we do different cases for big and small NR_CPUS:


    * Make it an array - that way passing it as an argument will
    * always pass it as a pointer!
    typedef unsigned long cpumask_t[1];

    static inline void create_cpumask(cpumask_t *p)
    *p = 0;
    static inline void free_cpumask(cpumask_t *p)


    typedef unsigned long *cpumask_t;

    static inline void create_cpumask(cpumask_t *p)
    *p = kcalloc(..);

    static inline void free_cpumask(cpumask_t *p)


    and now after you do this, you can just do something like

    cpumask_t mycpu;


    and in between, you can use 'cpumask' as a pointer, because even when it
    is an array directly allocated on the stack, the array can always
    degenerate into a pointer by C type rules!

    And for the small-NR_CPUS case there is zero overhead.


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      Last update: 2008-08-26 18:57    [W:0.021 / U:0.768 seconds]
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