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Date: Thu, 25 Aug 2016 17:25:53 +0200 (CEST)
From: Thomas Gleixner <tglx@linutronix.de>
To: Nicolai Stange <nicstange@gmail.com>
cc: John Stultz <john.stultz@linaro.org>, linux-kernel@vger.kernel.org
Subject: Re: [RFC v4 22/22] timekeeping: inform clockevents about freq
 adjustments
In-Reply-To: <20160822233320.4548-23-nicstange@gmail.com>
Message-ID: <alpine.DEB.2.20.1608251714230.5714@nanos>
References: <20160822233320.4548-1-nicstange@gmail.com> <20160822233320.4548-23-nicstange@gmail.com>
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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