linux-kernel - Re: [PATCH 2/4] time: add a notifier chain for when the system time is stepped

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Date:	Mon, 24 Jun 2013 21:55:46 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	David Vrabel <david.vrabel@...rix.com>
cc:	xen-devel@...ts.xen.org,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	LKML <linux-kernel@...r.kernel.org>,
	John Stultz <john.stultz@...aro.org>,
	Ingo Molnar <mingo@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH 2/4] time: add a notifier chain for when the system time
 is stepped

On Mon, 24 Jun 2013, David Vrabel wrote:

> On 24/06/13 17:30, Thomas Gleixner wrote:
> > 
> > We already have a synchronous notifier in place and the notifier call
> > itself is not expensive. What's expensive is the hypercall and there
> > is no way at the moment to figure out whether the update is relevant
> > for you or just a tick. Though that's trivial information to provide
> > without imposing another notifier including the surrounding mess on
> > the core code.
> 
> This looks good, thanks.
> 
> > --- a/kernel/time/timekeeping.c
> > +++ b/kernel/time/timekeeping.c
> [...]
> > @@ -508,7 +509,7 @@ int do_settimeofday(const struct timespec *tv)
> >  
> >  	tk_set_xtime(tk, tv);
> >  
> > -	timekeeping_update(tk, true, true);
> > +	timekeeping_update(tk, true, true, true);
> 
> These three booleans in a row is getting a bit opaque. How about I also
> change it to a set of flags?  e.g.,
> 
> timekeeping_updated(tk, TK_CLEAR_NTP | TK_MIRROR | TK_CLOCK_WAS_SET);

Fair enough. Can you convert the existing booleans first and then put
the CLOCK_WAS_SET patch on top of that?

Thanks,

	tglx

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