On Fri, 11 Jul 2014, Mathieu Desnoyers wrote:
> ----- Original Message -----
> > From: "Thomas Gleixner" <[email protected]>
> > To: "LKML" <[email protected]>
> > Cc: "John Stultz" <[email protected]>, "Peter Zijlstra"
> > <[email protected]>, "Steven Rostedt"
> > <[email protected]>, "Mathieu Desnoyers" <[email protected]>
> > Sent: Friday, July 11, 2014 9:45:19 AM
> > Subject: [patch 54/55] timekeeping: Provide fast and NMI safe access to
> > CLOCK_MONOTONIC[_RAW]
> > On the update side:
> >
> > tkf->seq++;
> > smp_wmb();
> > update(tkf->base[0], tk;
>
> missing ")"
:)
> Any reason why the updater wouldn't do:
>
> tkf->seq++;
> smp_wmb();
> update(tkf->base[1 - (tkf->seq & 0x01)], tk);
>
> instead of updating both array entries each time ?
base[0]; <- Current active
seq++; -> Makes base[1] the active one for readers
update(base[0]);
So readers are always one update cycle behind. Probably not an issue
most of the time, but think about fast wrapping clocksources and
NOHZ....
Thanks,
tglx
--
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/
