Re: [PATCH v9 3/5] qrwlock, x86 - Treat all data type not biggerthan long as atomic in x86

[Waiman Long]

On 01/21/2014 10:39 AM, Peter Zijlstra wrote:
> On Tue, Jan 21, 2014 at 10:36:48AM -0500, Waiman Long wrote:
> > On 01/20/2014 10:03 AM, Peter Zijlstra wrote:
> > > On Tue, Jan 14, 2014 at 11:44:05PM -0500, Waiman Long wrote:
> > > > The generic __native_word() macro defined in include/linux/compiler.h
> > > > only allows "int" and "long" data types to be treated as native and
> > > > atomic. The x86 architecture, however, allow the use of char and short
> > > > data types as atomic as well.
> > > >
> > > > This patch extends the data type allowed in the __native_word() macro to
> > > > allow the use of char and short.
> > > >
> > > > Signed-off-by: Waiman Long<Waiman.Long@xxxxxx>
> > > > ---
> > > >   arch/x86/include/asm/barrier.h |    8 ++++++++
> > > >   1 files changed, 8 insertions(+), 0 deletions(-)
> > > >
> > > > diff --git a/arch/x86/include/asm/barrier.h b/arch/x86/include/asm/barrier.h
> > > > index 04a4890..4d3e30a 100644
> > > > --- a/arch/x86/include/asm/barrier.h
> > > > +++ b/arch/x86/include/asm/barrier.h
> > > > @@ -24,6 +24,14 @@
> > > >   #define wmb()	asm volatile("sfence" ::: "memory")
> > > >   #endif
> > > >
> > > > +/*
> > > > + * All data types<= long are atomic in x86
> > > > + */
> > > > +#ifdef __native_word
> > > > +#undef __native_word
> > > > +#endif
> > > > +#define __native_word(t)	(sizeof(t)<= sizeof(long))
> > > Yeah, not going to happen.
> > Does explicit list of acceptable sizes work for you?
> >
> > #define __native_word(t) (sizeof(t) == sizeof(char) || sizeof(t) ==
> > sizeof(short) || sizeof(t) == sizeof(int ) ||
> >                   sizeof(t) == sizeof(long))
> No, generic primitives should not have arch specific behaviour.

OK, will something like the following acceptable to you:

arch/x86/include/asm/barrier.h:

#define __arch_native_word(t) (sizeof(t) == sizeof(char) || sizeof(t) ==
sizeof(short) || sizeof(t) == sizeof(int ) ||
                 sizeof(t) == sizeof(long))

include/linux/compiler.h:

#ifndef __native_word
# ifdef __arch_native_word(t)
#  define __native_word(t)	__arch_native_word(t)
# else
#  define __native_word(t) (sizeof(t) == sizeof(int) || sizeof(t) == sizeof(long))
# endif
#endif

-Longman




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