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    SubjectRe: [PULL] cpumask: finally make them variable size w/ CPUMASK_OFFSTACK.

    * Rusty Russell <rusty@rustcorp.com.au> wrote:

    > Hi Ingo,
    >
    > I finally rebased this on top of your tip tree, and tested it
    > locally. Some more old-style cpumask usages have crept in, but it's a
    > fairly simple series.

    Cool! Most of it looks pretty sane. I have a question about the
    gist of the series:

    > commit 898eb73305e2277be91b931c5a75484f8c87ae36
    > Author: Rusty Russell <rusty@rustcorp.com.au>
    > Date: Wed May 9 15:01:15 2012 +0930
    >
    > cpumask: remove struct cpumask definition when CONFIG_CPUMASK_OFFSTACK=y
    >
    > We're about to change CONFIG_CPUMASK_OFFSTACK so it only allocate
    > nr_cpu_ids bits for all cpumasks. We need to make sure that when
    > CONFIG_CPUMASK_OFFSTACK is set:
    >
    > 1) Noone uses the old bitmap ops, which use NR_CPUS bits (use cpumask_*)
    > 2) Noone uses assignment of struct cpumask (use cpumask_copy)
    > 3) Noone passes a struct cpumask (pass a pointer)
    > 4) Noone declares them on the stack (use cpumask_var_t)
    >
    > So we finally remove the definition of struct cpumask when
    > CONFIG_CPUMASK_OFFSTACK=y. This means that these usages will hit a compile
    > error the moment that config option is turned on.
    >
    > Note that it also means you can't declare a static cpumask. You
    > should avoid this anyway (use cpumask_var_t), but there's a
    > deliberately-ugly workaround for special cases, using DECLARE_BITMAP()
    > and to_cpumask().
    >
    > Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
    > Cc: Arnd Bergmann <arnd@arndb.de>
    > Cc: anton@samba.org
    > Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
    > Cc: Mike Travis <travis@sgi.com>

    Is there any good reason to not remove it altogether, regardless
    of whether the OFFSTACK config is set? I mean, triggering build
    failures for a relatively rarely turned on config option is
    asking for constant maintenance trouble.

    Thanks,

    Ingo


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