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

[Steven Rostedt <rostedt@goodmis.org>]

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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