[PATCH 1/3] powerpc/spinlocks: Refactor SHARED_PROCESSOR

[Christopher M Riedl]

> On July 30, 2019 at 4:31 PM Thiago Jung Bauermann <bauerman at linux.ibm.com> wrote:
> 
> 
> 
> Christopher M. Riedl <cmr at informatik.wtf> writes:
> 
> > Determining if a processor is in shared processor mode is not a constant
> > so don't hide it behind a #define.
> >
> > Signed-off-by: Christopher M. Riedl <cmr at informatik.wtf>
> > ---
> >  arch/powerpc/include/asm/spinlock.h | 21 +++++++++++++++------
> >  1 file changed, 15 insertions(+), 6 deletions(-)
> >
> > diff --git a/arch/powerpc/include/asm/spinlock.h b/arch/powerpc/include/asm/spinlock.h
> > index a47f827bc5f1..8631b0b4e109 100644
> > --- a/arch/powerpc/include/asm/spinlock.h
> > +++ b/arch/powerpc/include/asm/spinlock.h
> > @@ -101,15 +101,24 @@ static inline int arch_spin_trylock(arch_spinlock_t *lock)
> >
> >  #if defined(CONFIG_PPC_SPLPAR)
> >  /* We only yield to the hypervisor if we are in shared processor mode */
> > -#define SHARED_PROCESSOR (lppaca_shared_proc(local_paca->lppaca_ptr))
> >  extern void __spin_yield(arch_spinlock_t *lock);
> >  extern void __rw_yield(arch_rwlock_t *lock);
> >  #else /* SPLPAR */
> >  #define __spin_yield(x)	barrier()
> >  #define __rw_yield(x)	barrier()
> > -#define SHARED_PROCESSOR	0
> >  #endif
> >
> > +static inline bool is_shared_processor(void)
> > +{
> > +/* Only server processors have an lppaca struct */
> > +#ifdef CONFIG_PPC_BOOK3S
> > +	return (IS_ENABLED(CONFIG_PPC_SPLPAR) &&
> > +		lppaca_shared_proc(local_paca->lppaca_ptr));
> > +#else
> > +	return false;
> > +#endif
> > +}
> > +
> 
> CONFIG_PPC_SPLPAR depends on CONFIG_PPC_PSERIES, which depends on
> CONFIG_PPC_BOOK3S so the #ifdef above is unnecessary:
> 
> if CONFIG_PPC_BOOK3S is unset then CONFIG_PPC_SPLPAR will be unset as
> well and the return expression should short-circuit to false.
> 

Agreed, but the #ifdef is necessary to compile platforms which include
this header but do not implement lppaca_shared_proc(...) and friends.
I can reword the comment if that helps.

> --
> Thiago Jung Bauermann
> IBM Linux Technology Center