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    SubjectRe: Problem with commit deda2e81961e96be4f2c09328baca4710a2fd1a0
    On Thu, Aug 12, 2010 at 1:18 PM, Larry Finger <Larry.Finger@lwfinger.net> wrote:
    >
    > With the above commit, building an i386 version of the kernel results in the
    > following from the build:
    >
    > kernel/built-in.o: In function `logarithmic_accumulation':
    > /home/finger/linux-realtek/kernel/time/timekeeping.c:715: undefined reference to
    > `__umoddi3'
    > /home/finger/linux-realtek/kernel/time/timekeeping.c:715: undefined reference to
    > `__udivdi3'
    > make: *** [.tmp_vmlinux1] Error 1
    >
    > Reverting the patch allows the system to build correctly.

    Damn. It's your compiler turning a while-loop into a divide. Which
    likely isn't even an optimization, but whatever.

    John: I think that while-loop needs to be something like

    if (raw_nsecs >= NSEC_PER_SEC) {
    u64 raw_secs = raw_nsecs;
    raw_nsecs = do_div(raw_secs, NSEC_PER_SEC);
    raw_time.tv_sec += taw_secs;
    }
    raw_time.tc_nsec = raw_nsecs;

    which is sad and overly complicated, but the simple thing seems to get
    messed up by the compiler.

    Untested. Maybe I got the complex do_div() semantics wrong. Somebody
    needs to check.

    Linus


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