Re: [RFC v4 22/22] timekeeping: inform clockevents about freq adjustments

From	Thomas Gleixner <tglx@linutronix.de>
Newsgroups	linux.kernel
Subject	Re: [RFC v4 22/22] timekeeping: inform clockevents about freq adjustments
Date	2016-08-25 17:30 +0200
Message-ID	<sa4Lo-2LX-29@gated-at.bofh.it> (permalink)
References	<s96YV-4v1-5@gated-at.bofh.it> <s96YW-4v1-37@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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On Tue, 23 Aug 2016, Nicolai Stange wrote:
> +	raw_spin_lock_irqsave(&clockevents_lock, flags);
> +	list_for_each_entry(dev, &clockevent_devices, list) {
> +		if (!(dev->features & CLOCK_EVT_FEAT_ONESHOT))
> +			continue;
> +
> +		mult_raw = dev->mult;
> +		if (mult_raw != last_mult_raw) {
> +			last_mult_raw = mult_raw;
> +			last_mult_adjusted =
> +				__clockevents_calc_adjust_freq(mult_raw,
> +							mult_cs_mono,
> +							mult_cs_raw);

What makes sure that the resulting shift/mult pair is still valid after this
adjustment? The non adjusted mult/shift pair might be right at the border of
potential overflows and the adjustment might just put it over the edge....
We need at least sanity checks here.

Thanks,

	tglx

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[RFC v4 22/22] timekeeping: inform clockevents about freq adjustments Nicolai Stange <nicstange@gmail.com> - 2016-08-23 01:40 +0200
  Re: [RFC v4 22/22] timekeeping: inform clockevents about freq adjustments Nicolai Stange <nicstange@gmail.com> - 2016-08-24 11:50 +0200
  Re: [RFC v4 22/22] timekeeping: inform clockevents about freq  adjustments Thomas Gleixner <tglx@linutronix.de> - 2016-08-25 17:10 +0200
  Re: [RFC v4 22/22] timekeeping: inform clockevents about freq  adjustments Thomas Gleixner <tglx@linutronix.de> - 2016-08-25 17:30 +0200

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