linux-kernel - Re: [resend PATCH for 3.2] procfs: do not confuse jiffies with cputime64

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Date:	Thu, 22 Dec 2011 10:55:04 +0100
From:	Martin Schwidefsky <schwidefsky@...ibm.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Michal Hocko <mhocko@...e.cz>, Arnd Bergmann <arnd@...db.de>,
	linux-kernel@...r.kernel.org,
	"Artem S. Tashkinov" <t.artem@...lcity.com>,
	Dave Jones <davej@...hat.com>,
	Alexey Dobriyan <adobriyan@...il.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Andreas Schwab <schwab@...ux-m68k.org>
Subject: Re: [resend PATCH for 3.2] procfs: do not confuse jiffies with
 cputime64_t

On Wed, 21 Dec 2011 11:59:19 -0800
Andrew Morton <akpm@...ux-foundation.org> wrote:

> On Wed, 21 Dec 2011 11:03:34 +0100
> Michal Hocko <mhocko@...e.cz> wrote:
> 
> > Hmm, it seems that this bugfix (for 3.2) stalled. I guess that it is
> > primarily because it is multiarch fix.
> > I am sorry to bother you Andrew but could we push this through you,
> > please?
> > 
> > The full patch for reference:
> > ---
> > >From 1fca39b21f3b344c90c30d98db6dcdcdc6815797 Mon Sep 17 00:00:00 2001
> > From: Andreas Schwab <schwab@...ux-m68k.org>
> > Date: Mon, 12 Dec 2011 14:07:53 +0100
> > Subject: [PATCH] procfs: do not confuse jiffies with cputime64_t
> > 
> > get_{idle,iowait}_time are supposed to return cputime64_t values, not
> > jiffies.  Add usecs_to_cputime64 for this.
> 
> This makes a huge mess when mixed with Martin's "cputime: add sparse
> checking and cleanup" in linux-next.  I think I got it fixed up but it
> needs careful checking - I don't _think_ I needed to add more __force
> thingies.  The version against today's linux-next is below.

As long as cputime_t and cputime64_t have the same base type my version of
sparse does not warn if you mix the two types.
 
> (I did party tricks with this so I could carry the against-mainline and
> against-next versions in the same tree).
> 
> 
> Also, in include/asm-generic/cputime.h we have:
> 
> #define usecs_to_cputime64(__msecs)	nsecs_to_jiffies64((__msecs) * 1000)
> 
> But it would be neater to have used nsecs_to_cputime64(), surely.

It would be cleaner to do an explicit cast to cputime64_t for all of
the usecs_to_cputime64() definitions. 

-- 
blue skies,
   Martin.

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

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