* john stultz ([EMAIL PROTECTED]) wrote: > > On Wed, 2008-01-16 at 18:33 -0500, Steven Rostedt wrote: > > Thanks John for doing this! > > > > (comments imbedded) > > > > On Wed, 16 Jan 2008, john stultz wrote: > > > + int num = !cs->base_num; > > > + cycle_t offset = (now - cs->base[!num].cycle_base_last); > > > + offset &= cs->mask; > > > + cs->base[num].cycle_base = cs->base[!num].cycle_base + offset; > > > + cs->base[num].cycle_base_last = now; > > > > I would think that we would need some sort of barrier here. Otherwise, > > base_num could be updated before all the cycle_base. I'd expect a smp_wmb > > is needed. > > Hopefully addressed in the current version. > > > > > Index: monotonic-cleanup/kernel/time/timekeeping.c > > > =================================================================== > > > --- monotonic-cleanup.orig/kernel/time/timekeeping.c 2008-01-16 > > > 12:21:46.000000000 -0800 > > > +++ monotonic-cleanup/kernel/time/timekeeping.c 2008-01-16 > > > 14:15:31.000000000 -0800 > > > @@ -71,10 +71,12 @@ > > > */ > > > static inline s64 __get_nsec_offset(void) > > > { > > > - cycle_t cycle_delta; > > > + cycle_t now, cycle_delta; > > > s64 ns_offset; > > > > > > - cycle_delta = clocksource_get_cycles(clock, clocksource_read(clock)); > > > + now = clocksource_read(clock); > > > + cycle_delta = (now - clock->cycle_last) & clock->mask; > > > + cycle_delta += clock->cycle_accumulated; > > > > Is the above just to decouple the two methods? > > Yep. clocksource_get_cycles() ended up not being as useful as an helper > function (I was hoping the arch vsyscall implementations could use it, > but they've done too much optimization - although that may reflect a > need up the chain to the clocksource structure). >
The problem with vsyscall is that we will have a hard time disabling preemption :( Therefore, insuring that the read of the data is done in a timely manner is hard to do. Mathieu > thanks > -john > > -- Mathieu Desnoyers Computer Engineering Ph.D. Student, Ecole Polytechnique de Montreal OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/