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    SubjectRe: [Patch] Re: Nasty suprise with uptime
    On  1 Nov 01 at 1:52, Tim Schmielau wrote:

    > + static unsigned long jiffies_hi = 0;
    > + static unsigned long jiffies_last = INITIAL_JIFFIES;
    > + unsigned long jiffies_tmp;
    > +
    > + jiffies_tmp = jiffies; /* avoid races */
    > + if (jiffies_tmp < jiffies_last) /* We have a wrap */
    > + jiffies_hi++;
    > + jiffies_last = jiffies_tmp;

    There is very small race - if two processes will call get_jiffies64()
    at same time, they can both happen to test jiffies_tmp < jiffies_last
    with old jiffies_last - incrementing jiffies_hi twice :-( This race
    window is only few microseconds every 497 days, but if we want
    correct kernel...
    Best regards,
    Petr Vandrovec
    vandrove@vc.cvut.cz

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