linux-kernel - Re: Linux 3.1-rc9

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Message-ID: <20111024094817.30c01c9b@de.ibm.com>
Date:	Mon, 24 Oct 2011 09:48:17 +0200
From:	Martin Schwidefsky <schwidefsky@...ibm.com>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Simon Kirby <sim@...tway.ca>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Dave Jones <davej@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: Linux 3.1-rc9

On Sun, 23 Oct 2011 13:34:22 +0200
Ingo Molnar <mingo@...e.hu> wrote:

> 
> * Martin Schwidefsky <schwidefsky@...ibm.com> wrote:
> 
> > +#define cputime_zero			((__force cputime_t) 0ULL)
> > +#define cputime64_zero			((__force cputime64_t) 0ULL)
> 
> Hm, why are these still needed?
> 
> This:
> 
> 		if (*newval == cputime_zero)
> 			return;
> 
> Could be written as the much simpler:
> 
> 		if (!*newval)
>  			return;
> 
> with no ill effect that i can see.

These types are still there because cputime_t can be u32 or u64. E.g. this

  timer->expires.cpu = 0;

will give the following sparse warning

  kernel/posix-cpu-timers.c:463:46: warning: implicit cast to nocast type

if you architecture happens to have a u64 as cputime_t.
We could get rid of cputime64_t as it always should be a u64. To keep
things symmetrical I choose to keep both defines.

-- 
blue skies,
   Martin.

"Reality continues to ruin my life." - Calvin.

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