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    Subject[PATCH] trivial, document that div64_u64() is not precise on 32bit platforms
    We have a bugreport which blames div64_u64() on 32bit platforms.

    However, the code obviously doesn't even try to pretend it can do
    the 64bit division precisely. If there is something in the high
    word of divisor, div64_u64() just shifts both arguments and throws
    out the low bits.

    Add a small comment to avoid the confusion.

    Signed-off-by: Oleg Nesterov <>

    lib/div64.c | 5 ++++-
    1 file changed, 4 insertions(+), 1 deletion(-)

    --- a/lib/div64.c
    +++ b/lib/div64.c
    @@ -77,7 +77,10 @@ s64 div_s64_rem(s64 dividend, s32 diviso

    -/* 64bit divisor, dividend and result. dynamic precision */
    + * 64bit divisor, dividend and result. Dynamic precision, unless
    + * divisor fits in u32 result is not exactly correct.
    + */
    #ifndef div64_u64
    u64 div64_u64(u64 dividend, u64 divisor)

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      Last update: 2010-08-02 18:15    [W:0.018 / U:21.516 seconds]
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