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

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Message-ID: <51C87B26.3010904@citrix.com>
Date:	Mon, 24 Jun 2013 18:00:22 +0100
From:	David Vrabel <david.vrabel@...rix.com>
To:	Thomas Gleixner <tglx@...utronix.de>
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 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);

David
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