Re: [PATCH] sched: Support current clocksource handling in fallback sched_clock().

Paul Mundt
2009-05-28T16:40:11Z

On Thu, May 28, 2009 at 06:32:09PM +0200, Peter Zijlstra wrote:
> On Thu, 2009-05-28 at 09:13 -0700, Daniel Walker wrote:
> > On Thu, 2009-05-28 at 14:59 +0200, Peter Zijlstra wrote:
> > > CPU0 CPU1
> > >
> > > clock = ACCESS_ONCE(sched_clocksource);
> > >
> > > unload module
> > > clocksource_unregister()
> > > sched_clocksource = jiffies
> > > unmap data/text
> > >
> > > cyc2ns(clock, clocksource_read(clock)) <--- fireworks
> > >
> > >
> >
> > Do any module based clocksources even exist right now?
> > clocksource_unregister only seems to be used 3 times..
>
> Good point, it appears its not even exported.
>
> Thomas mentioned modules, I assumed.
>
The drivers/clocksource/ drivers in theory could be modular anyways.
Handling this transition properly is at least one less barrier to modular
clocksources, so I think it's progress regardless. I don't remember what
all of the other issues were though, John probably remembers.