[PATCH] ARM: include: asm: atomic.h: use type cast 's64' for the return value of atomic64_add_return().

[Russell King - ARM Linux]

On Tue, Sep 24, 2013 at 10:30:41AM +0100, Will Deacon wrote:
> On Sat, Sep 21, 2013 at 12:06:47PM +0100, Chen Gang wrote:
> > diff --git a/arch/arm/include/asm/atomic.h b/arch/arm/include/asm/atomic.h
> > index da1c77d..8cf005d 100644
> > --- a/arch/arm/include/asm/atomic.h
> > +++ b/arch/arm/include/asm/atomic.h
> > @@ -475,7 +475,7 @@ static inline int atomic64_add_unless(atomic64_t *v, u64 a, u64 u)
> >  	return ret;
> >  }
> >  
> > -#define atomic64_add_negative(a, v)	(atomic64_add_return((a), (v)) < 0)
> > +#define atomic64_add_negative(a, v)	((s64)atomic64_add_return((a), (v)) < 0)
> >  #define atomic64_inc(v)			atomic64_add(1LL, (v))
> >  #define atomic64_inc_return(v)		atomic64_add_return(1LL, (v))
> >  #define atomic64_inc_and_test(v)	(atomic64_inc_return(v) == 0)
> 
> Is this the right fix? It looks more like atomic[64]_t should be signed, but
> some 32-bit architectures (ARM, x86, tile) are actually implementing
> atomic64_t as u64. Furthermore, there are discrepencies in the operands to
> the various atomic64_* function (long long vs u64) which probably need
> sorting out.

Even though our underlying type is u64, we could change the arguments to
be 'long long' as per the asm-generic/atomic64.h version.  Remember that
this is ARM specific code, and we know that long long == 64-bit int.