linux-kernel - Re: [PATCH] sched/clock: cleanup, remove wrap

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Message-ID: <536A2143.5090106@cn.fujitsu.com>
Date:	Wed, 7 May 2014 21:04:19 +0900
From:	Dongsheng Yang <yangds.fnst@...fujitsu.com>
To:	Peter Zijlstra <peterz@...radead.org>
CC:	<mingo@...hat.com>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] sched/clock: cleanup, remove wrap_{max|min}().

On 05/07/2014 09:55 PM, Peter Zijlstra wrote:
> On Wed, May 07, 2014 at 08:48:58PM +0900, Dongsheng Yang wrote:
>> I am not sure why we need the wrap_{max|min}() in kernel/sched/clock.c.
>> But I checked the implementation of max() and min() in linux/kernel.h, I think
>> we can reuse them here rather than introduce a new function named
>> wrap_{max|min}().
> wrap is a good hint there.. they're supposed to deal with the clock
> wrapping. Of course 2^64 ns is a rather long time (~584 years in fact),
> but that doesn't mean we shouldn't care.
>
> And no, min/max don't do the right thing.

IMMO,  max() in kernel.h is checking and returning the u64 with typeof() if
we are passing a u64 parameter to max(). And I checked current callers 
of wrap_max(),
they are all passing parameters of u64 type. So I think max/min works 
well at
the place of wrap_max/min().

Maybe I am missing something here, please correct me if I understand it 
incorrectly.

Thanx
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