Re: [PATCH] timekeeping: drop irq-context clocksource polling

Andrew Morton
2007-04-05T21:36:59Z

On Thu, 05 Apr 2007 14:25:19 -0700
john stultz <johnstul@us.ibm.com> wrote:

> On Thu, 2007-04-05 at 14:03 -0700, Daniel Walker wrote:
> > Before this change the timekeeping code would poll the clocksource
> > list every interrupt. This changes that so the clocksource list is
> > only checked when there has been and update, and no longer checks
> > in interrupt context.
> >
> > This also has a few small space and line cleanups.
> >
> > Boot tested on i386, compile tested on x86_64 .. However, I couldn't
> > find a !GENERIC_TIME that compiled without this change so it's untested..
> >
> > Signed-Off-By: Daniel Walker <dwalker@mvista.com>
>
> Err.. I think you need to be holding a write on the xtime_lock (as is
> done before calling update_wall_time()) when changing the clocksource.

The patch does add the appropriate locking to change_clocksource(),
doesn't it?

It looks like a good change to me - we avoid taking the kernel-wide
clocksource_lock every tick?