Subject: Re: linux-next: tip tree build warnings

From: Martin Schwidefsky <[email-masked]>
Date: Mon, 7 Sep 2009 10:59:28 +0200

On Thu, 3 Sep 2009 14:13:26 +0200
Heiko Carstens <[email-masked]> wrote:

> On Thu, Sep 03, 2009 at 10:38:44AM +0200, Ingo Molnar wrote:
> > * Stephen Rothwell <[email-masked]> wrote:
> > > cputime_t is variously "u64", "unsigned long long" and "unsigned 
> > > long" on different architectures.
> > 
> > Should be unsigned long i think. Most architectures use it as 
> > unsigned long via include/asm-generic/cputime.h, except these three:
> > 
> >  arch/ia64/include/asm/cputime.h:typedef u64 cputime_t;
> >  arch/powerpc/include/asm/cputime.h:typedef u64 cputime_t;
> >  arch/s390/include/asm/cputime.h:typedef unsigned long long cputime_t;
> > 
> > Or we could eliminate the type altogether as well and standardize on 
> > u64. Thomas?
> 
> s390 uses 64 bit cputime_t because we want the high resolution also in
> 32 bit kernels. So standardizing on u64 would be the preferred solution
> for us.

The cputime_t type serves/served two purposes: 1) make it clear that
this is NOT a jiffie value, it is an architecture defined type with
architecture dependent semantic, 2) by redefining cputime_t to a
structure with a single embedded unsigned long I have been able to
identify all places in the kernel that do not use the proper cputime
functions. I'm not sure if we need 2) anymore.

-- 
blue skies,
   Martin.

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