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    SubjectRe: Problem with commit deda2e81961e96be4f2c09328baca4710a2fd1a0
    On 08/12/2010 03:26 PM, Linus Torvalds wrote:
    > 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.

    I'll try it. The system with the problem has gcc (SUSE Linux) 4.3.2
    [gcc-4_3-branch revision 141291]. That is on a 64-bit system cross compiling
    with ARCH=i386.

    The real 32-bit system with gcc (SUSE Linux) 4.5.0 20100604 [gcc-4_5-branch
    revision 160292] builds OK. It just wasn't finished when I wrote the first message.

    Larry



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