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Date: Mon, 24 Jun 2013 18:00:22 +0100
From: David Vrabel <david.vrabel@citrix.com>
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To: Thomas Gleixner <tglx@linutronix.de>
CC: <xen-devel@lists.xen.org>, Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
        LKML <linux-kernel@vger.kernel.org>,
        John Stultz <john.stultz@linaro.org>, Ingo Molnar <mingo@kernel.org>,
        Peter Zijlstra <peterz@infradead.org>
Subject: Re: [PATCH 2/4] time: add a notifier chain for when the system time
 is stepped
References: <1371755792-25962-1-git-send-email-david.vrabel@citrix.com> <1371755792-25962-3-git-send-email-david.vrabel@citrix.com> <alpine.DEB.2.02.1306210953480.4013@ionos.tec.linutronix.de> <51C44A09.9010402@citrix.com> <alpine.DEB.2.02.1306212328350.4013@ionos.tec.linutronix.de> <51C824A8.1080305@citrix.com> <alpine.DEB.2.02.1306241753080.4013@ionos.tec.linutronix.de>
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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