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    SubjectRe: [PATCH net-next] time: jiffies_delta_to_clock_t() helper to the rescue
    On Thu, 9 Aug 2012, Eric Dumazet wrote:

    > From: Eric Dumazet <edumazet@google.com>
    >
    > Various /proc/net files sometimes report crazy timer values, expressed
    > in clock_t units.
    >
    > This happens when an expired timer delta (expires - jiffies) is passed
    > to jiffies_to_clock_t().
    >
    > This function has an overflow in :
    >
    > return div_u64((u64)x * TICK_NSEC, NSEC_PER_SEC / USER_HZ);
    >
    > commit cbbc719fccdb8cb (time: Change jiffies_to_clock_t() argument type
    > to unsigned long) only got around the problem.
    >
    > As we cant output negative values in /proc/net/tcp without breaking
    > various tools, I suggest adding a jiffies_delta_to_clock_t() wrapper
    > that caps the negative delta to a 0 value.

    That's correct for 64bit, but for 32bit you do the same for valid
    timer values where expires < jiffies. So you might output 0 for valid
    armed timers for quite a while around the point where jiffies are
    close to the wrapping point.

    Dunno if that's an issue, but it want's to be documented at least.

    Thanks,

    tglx


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