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    SubjectRe: Ktimer / -rt9 (+custom) monotonic_clock going backwards.

    On Thu, 20 Oct 2005, Ingo Molnar wrote:

    >
    > * Steven Rostedt <rostedt@goodmis.org> wrote:
    >
    > > static inline nsec_t __get_nsec_offset(void)
    > > {
    > > cycle_t cycle_now, cycle_delta;
    > > nsec_t ns_offset;
    > >
    > > /* read clocksource */
    > > cycle_now = read_clocksource(clock);
    > >
    > > /* calculate the delta since the last timeofday_periodic_hook */
    > > cycle_delta = (cycle_now - cycle_last) & clock->mask;
    > >
    > > /* convert to nanoseconds */
    > > ns_offset = cyc2ns(clock, ntp_adj, cycle_delta);
    > >
    > > /* Special case for jiffies tick/offset based systems
    > > * add arch specific offset
    > > */
    > > ns_offset += arch_getoffset();
    > >
    > > return ns_offset;
    > > }
    > >
    > > cycle_now is 32 bits. If the clocksource overflows (which it can in
    > > 30 seconds) the cyclec_delta will be wrong.
    >
    > isnt cycle_t 64 bits?
    >

    Not anymore.

    include/linux/time.h:

    /* timeofday base types */
    typedef s64 nsec_t;
    typedef unsigned long cycle_t;

    -- Steve

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