linux-kernel - Re: [PATCH 06/12] time: Add infrastructure to cap clocksource reads to the max

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Message-ID: <20150124173514.GA4784@localhost.localdomain>
Date:	Sat, 24 Jan 2015 18:35:15 +0100
From:	Richard Cochran <richardcochran@...il.com>
To:	John Stultz <john.stultz@...aro.org>
Cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Dave Jones <davej@...emonkey.org.uk>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Prarit Bhargava <prarit@...hat.com>,
	Stephen Boyd <sboyd@...eaurora.org>,
	Ingo Molnar <mingo@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH 06/12] time: Add infrastructure to cap clocksource reads
 to the max_cycles value

On Thu, Jan 22, 2015 at 04:09:21PM -0800, John Stultz wrote:
> +static inline cycle_t timekeeping_get_delta(struct tk_read_base *tkr)
> +{
> +	cycle_t cycle_now, delta;
> +
> +	/* read clocksource */
> +	cycle_now = tkr->read(tkr->clock);
> +
> +	/* calculate the delta since the last update_wall_time */
> +	delta = clocksource_delta(cycle_now, tkr->cycle_last, tkr->mask);
> +
> +	/* Cap delta value to the max_cycles values to avoid mult overflows */
> +	if (unlikely(delta > tkr->clock->max_cycles))
> +		delta = tkr->clock->max_cycles;
> +
> +	return delta;
> +}
>  #else
>  #define timekeeping_check_update(x, y)
> +static inline cycle_t timekeeping_get_delta(struct tk_read_base *tkr)
> +{
> +	/* calculate the delta since the last update_wall_time */
> +	return clocksource_delta(tkr->read(tkr->clock), tkr->cycle_last,
> +								tkr->mask);

Coding style is strange here.  It would look nicer it were like the
debug version, above.

> +}
>  #endif

Series looks fine to me.

Acked-by: Richard Cochran <richardcochran@...il.com>
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