linux-kernel - Re: [tip:timers/core] time: Refactor msecs_to

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Message-ID: <20150519144744.GA30261@opentech.at>
Date:	Tue, 19 May 2015 16:47:44 +0200
From:	Nicholas Mc Guire <der.herr@...r.at>
To:	Joe Perches <joe@...ches.com>
Cc:	yamada.m@...panasonic.com, linux-kernel@...r.kernel.org,
	sam@...nborg.org, hpa@...or.com, john.stultz@...aro.org,
	mmarek@...e.cz, hofrat@...dl.org, tglx@...utronix.de,
	mingo@...nel.org, pjt@...gle.com, ahh@...gle.com
Subject: Re: [tip:timers/core] time: Refactor msecs_to_jiffies

On Tue, 19 May 2015, Joe Perches wrote:

> On Tue, 2015-05-19 at 06:36 -0700, tip-bot for Nicholas Mc Guire wrote:
> > Refactor the msecs_to_jiffies conditional code part in time.c and 
> > jiffies.h putting it into conditional functions rather than #ifdefs
> > to improve readability.
> []
> > diff --git a/include/linux/jiffies.h b/include/linux/jiffies.h
> []
> > +static inline unsigned long _msecs_to_jiffies(const unsigned int m)
> > +{
> > +		return (m + (MSEC_PER_SEC / HZ) - 1) / (MSEC_PER_SEC / HZ);
> > +}
> > +#elif HZ > MSEC_PER_SEC && !(HZ % MSEC_PER_SEC)
> > +/*
> > + * HZ is larger than 1000, and HZ is a nice round multiple of 1000 -
> > + * simply multiply with the factor between them.
> > + *
> > + * But first make sure the multiplication result cannot overflow:
> > + */
> > +static inline unsigned long _msecs_to_jiffies(const unsigned int m)
> > +{
> > +		if (m > jiffies_to_msecs(MAX_JIFFY_OFFSET))
> > +			return MAX_JIFFY_OFFSET;
> > +		return m * (HZ / MSEC_PER_SEC);
> > +}
> > +#else
> > +/*
> > + * Generic case - multiply, round and divide. But first check that if
> > + * we are doing a net multiplication, that we wouldn't overflow:
> > + */
> > +static inline unsigned long _msecs_to_jiffies(const unsigned int m)
> > +{
> > +		if (HZ > MSEC_PER_SEC && m > jiffies_to_msecs(MAX_JIFFY_OFFSET))
> > +			return MAX_JIFFY_OFFSET;
> > +
> > +		return (MSEC_TO_HZ_MUL32 * m + MSEC_TO_HZ_ADJ32)
> > +			>> MSEC_TO_HZ_SHR32;
> > +}
> > +#endif
> 
> It'd be nicer to remove 1 level of unnecessary tab indentation in
> all the _msecs_to_jiffies functions here.
>
oops - sorry - no idea how I did that - will fix up and resend

thx!
hofrat 
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