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    Subject[Patch 1/6] Delay accounting: timespec diff
    nstimestamp_diff.patch

    Add kernel utility function for measuring the
    interval (diff) between two timespec values, adjusting for overflow

    Signed-off-by: Shailabh Nagar <nagar@watson.ibm.com>

    include/linux/time.h | 15 +++++++++++++++
    1 files changed, 15 insertions(+)

    Index: linux-2.6.15-rc7/include/linux/time.h
    ===================================================================
    --- linux-2.6.15-rc7.orig/include/linux/time.h
    +++ linux-2.6.15-rc7/include/linux/time.h
    @@ -114,6 +114,21 @@ set_normalized_timespec (struct timespec
    ts->tv_nsec = nsec;
    }

    +/*
    + * timespec_diff_ns - Return difference of two timestamps in nanoseconds
    + * In the rare case of @end being earlier than @start, return zero
    + */
    +static inline unsigned long long
    +timespec_diff_ns(struct timespec *start, struct timespec *end)
    +{
    + long long ret;
    +
    + ret = end->tv_sec*(1000000000) + end->tv_nsec;
    + ret -= start->tv_sec*(1000000000) + start->tv_nsec;
    + if (ret < 0)
    + return 0;
    + return ret;
    +}
    #endif /* __KERNEL__ */

    #define NFDBITS __NFDBITS
    -
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