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    SubjectRe: 2.6.22-rc3-mm1: __attribute__((weak)) considered harmful
    On Tue, Jun 05, 2007 at 01:52:38AM +0200, Martin Peschke wrote:
    > Andrew Morton wrote:
    > >On Sat, 2 Jun 2007 19:14:25 +0200
    > >Adrian Bunk <bunk@stusta.de> wrote:
    > >
    > >>statistics-infrastructure-make-printk_clock-a-generic-kernel-wide-nsec-resolution.patch
    > >>shows why __attribute__((weak)) is harmful because you don't see if a
    > >>required non-weak implemtation is missing:
    > >>
    > >>In this case, the weak printk_clock() was renamed to timestamp_clock(),
    > >>but the ARM and i386 implementations weren't renamed...
    > >>
    > >
    > >printk_clock() is sched_clock() in disguise, and I'm not sure that making
    > >sched_clock() more widely available in this fashion is something that we
    > >want to do anyway.

    Note that sched_clock() can not be used early on ARM; it might want to
    access MMIO which is not accessible until later in setup_arch(). This
    is why ARM's printk_clock() divorces itself from sched_clock().

    > As to timestamp_clock(): its useful for statistics, but still a minor
    > feature. It would be unfortuante if that was the stumbling block for my
    > patches. Am I right that the fix for the issue pointed at by Adrian is to
    > rename those two occurrences of printk_clock()? Do you want me to submit a
    > patch?

    If it's ends up being based upon sched_clock() instead of printk_clock()
    on ARM then it'll break stuff horribly (== non-bootable kernels.)

    --
    Russell King
    Linux kernel 2.6 ARM Linux - http://www.arm.linux.org.uk/
    maintainer of:
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