linux-kernel - Re: [PATCH 09/11] cputime:Introduce the cputime_to_timespec64/timespec64_to

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Message-ID: <alpine.DEB.2.11.1504202249590.13914@nanos>
Date:	Mon, 20 Apr 2015 23:09:17 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Baolin Wang <baolin.wang@...aro.org>
cc:	arnd@...db.de, john.stultz@...aro.org, heenasirwani@...il.com,
	pang.xunlei@...aro.org, peterz@...radead.org,
	rafael.j.wysocki@...el.com, gregkh@...uxfoundation.org,
	richardcochran@...il.com, benh@...nel.crashing.org,
	paulus@...ba.org, mpe@...erman.id.au, schwidefsky@...ibm.com,
	heiko.carstens@...ibm.com, linux390@...ibm.com, rth@...ddle.net,
	riel@...hat.com, cl@...ux.com, tj@...nel.org, fweisbec@...il.com,
	ahh@...gle.com, pjt@...gle.com, linuxppc-dev@...ts.ozlabs.org,
	linux-s390@...r.kernel.org, linux-arch@...r.kernel.org,
	linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
	y2038@...ts.linaro.org
Subject: Re: [PATCH 09/11] cputime:Introduce the cputime_to_timespec64/timespec64_to_cputime
 function

On Mon, 20 Apr 2015, Baolin Wang wrote:

> This patch introduces some functions for converting cputime to timespec64 and back,
> that repalce the timespec type with timespec64 type, as well as for arch/s390 and
> arch/powerpc architecture.

No. We want a patch which adds the functions and then a patch which
uses them. This stuff is tricky and hard to review. So please split
the patches into smaller chunks.

> +unsigned long
> +timespec64_to_jiffies(const struct timespec64 *value)
> +{
> +	return __timespec_to_jiffies(value->tv_sec, value->tv_nsec);
> +}
> +EXPORT_SYMBOL(timespec64_to_jiffies);

So we have now two exports which are doing exactly the same
thing. Copy and paste is wonderful, right?

What about exporting __timespec_to_jiffies() and providing inlines for
timespec_to_jiffies() and timespec64_to_jiffies() ?

EXPORT_SYMBOL is not just a stupid annotation. Its impact on the
resulting kernel size is larger than the actual function
implementation.

> +void
> +jiffies_to_timespec64(const unsigned long jiffies, struct timespec64 *value)
> +{
> +	/*
> +	 * Convert jiffies to nanoseconds and separate with
> +	 * one divide.
> +	 */
> +	u32 rem;
> +	value->tv_sec = div_u64_rem((u64)jiffies * TICK_NSEC,
> +				   NSEC_PER_SEC, &rem);
> +	value->tv_nsec = rem;
> +}
> +EXPORT_SYMBOL(jiffies_to_timespec64);

Sigh.

Thanks,

	tglx


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