linux-kernel - Re: [PATCH RFC V1 4/5] timekeeping: Offer an interface to manipulate leap seconds.

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Message-ID: <4FA80832.80403@linaro.org>
Date:	Mon, 07 May 2012 10:36:50 -0700
From:	John Stultz <john.stultz@...aro.org>
To:	Richard Cochran <richardcochran@...il.com>
CC:	linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH RFC V1 4/5] timekeeping: Offer an interface to manipulate
 leap seconds.

On 05/05/2012 03:17 AM, Richard Cochran wrote:
> On Fri, Apr 27, 2012 at 04:08:03PM -0700, John Stultz wrote:
>> On 04/27/2012 01:12 AM, Richard Cochran wrote:
>>
>>> +#ifdef CONFIG_DELETE_LEAP_SECONDS
>>> +	/* Remembers whether to insert or to delete. */
>>> +	int insert_leapsecond;
>>> +#endif
>> I'm not a big fan of this additional config option.  The maintenance
>> burden for the extra condition is probably not worth the code size
>> trade-off.  Or it needs way more justification.
> Out of curiosity, I looked at ntp-4.2.6p5 to see if they really
> support deleting leap seconds or not. Even though the code appears to
> try and support them, I spotted a few bugs. There is a hard coded
> assumption that the TAI offset is increasing.
>
> This is just the reason why I suggest not supporting deletions (or
> only conditionally for nit pickers). You can code it up, but it will
> be in vain, since the code will never be tested or used in practice.
> Code that is never executed is a true mainenance burden by definition.
>
Well, testing it from a kernel perspective isn't a problem as its easy 
to write up a userland app that exercises the code path. But I agree its 
unlikely to be used in practice.

And you're argument of the added maintenance burden is reasonable. And 
while I don't find it terrible to keep, I'd *much* rather just remove it 
then add a config option and more #ifdefery.  Even so, such a removal 
needs to be an independent patch that can be discussed and argued on its 
own without mixing in other features.

thanks
-john

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