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    From
    SubjectRe: 2.1.125 Show stopper list: Draft
    Date
    > >   Jiffy Handling
    > > Many drivers still do not handle jiffy overflows nicely
    >
    > Alan, should we consider this really a bug? I think that to only _clean_
    > way to fix this problem would be to use a long long C type for jiffies
    > (decreasing performance). But decreasing performance is needed also to
    > catch the overflow...

    It is a bug. The only drivers that should have a problem are those that
    need to execute 250 day delay loops. Now I grant an NCR5380 is slow but
    its not that slow...

    There are also macros in the kernel tree now for time comparison with wrap
    around protection. Basically it uses a tcp like scheme so that the low 32bits
    are used for a 31bit relative range.

    So instead of

    x=jiffes+HZ/5
    while(jiffies<x)
    {
    if(it_worked())
    break;
    }

    You do

    x=jiffies+HZ/5

    while(time_before(jiffies,x))
    {
    ...

    and the end result is safe over the 498 day timer. And yes I consider
    this an issue...

    2:31am up 482 days, 6:24, 1 user, load average: 0.09, 0.08, 0.08

    Alan


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