Subject: Re: [RFC PATCH for 4.14 1/2] membarrier: Remove unused code for architectures without membarrier hooks

From: "Paul E. McKenney" <[email-masked]>
Date: Fri, 6 Oct 2017 14:08:01 -0700

On Thu, Oct 05, 2017 at 06:33:26PM -0400, Mathieu Desnoyers wrote:
> Architectures without membarrier hooks don't need to emit the
> empty membarrier_arch_switch_mm() static inline when
> CONFIG_MEMBARRIER=y.
> 
> Adapt the CONFIG_MEMBARRIER=n counterpart to only emit the empty
> membarrier_arch_switch_mm() for architectures with membarrier hooks.
> 
> Reported-by: Nicholas Piggin <[email-masked]>
> Signed-off-by: Mathieu Desnoyers <[email-masked]>

Queued for further review and testing, targeting v4.15.  Please let me
know if you need it sooner.

							Thanx, Paul

> CC: Peter Zijlstra <[email-masked]>
> CC: Paul E. McKenney <[email-masked]>
> CC: Boqun Feng <[email-masked]>
> CC: Andrew Hunter <[email-masked]>
> CC: Maged Michael <[email-masked]>
> CC: [email-masked]
> CC: Avi Kivity <[email-masked]>
> CC: Benjamin Herrenschmidt <[email-masked]>
> CC: Paul Mackerras <[email-masked]>
> CC: Michael Ellerman <[email-masked]>
> CC: Dave Watson <[email-masked]>
> CC: Alan Stern <[email-masked]>
> CC: Will Deacon <[email-masked]>
> CC: Andy Lutomirski <[email-masked]>
> CC: Ingo Molnar <[email-masked]>
> CC: Alexander Viro <[email-masked]>
> CC: [email-masked]
> CC: [email-masked]
> ---
>  include/linux/sched/mm.h | 6 ++----
>  1 file changed, 2 insertions(+), 4 deletions(-)
> 
> diff --git a/include/linux/sched/mm.h b/include/linux/sched/mm.h
> index d5a9ab8f3836..b2767ecb21a8 100644
> --- a/include/linux/sched/mm.h
> +++ b/include/linux/sched/mm.h
> @@ -215,10 +215,6 @@ static inline void memalloc_noreclaim_restore(unsigned int flags)
>  #ifdef CONFIG_ARCH_HAS_MEMBARRIER_HOOKS
>  #include <asm/membarrier.h>
>  #else
> -static inline void membarrier_arch_switch_mm(struct mm_struct *prev,
> -		struct mm_struct *next, struct task_struct *tsk)
> -{
> -}
>  static inline void membarrier_arch_fork(struct task_struct *t,
>  		unsigned long clone_flags)
>  {
> @@ -247,10 +243,12 @@ static inline void membarrier_execve(struct task_struct *t)
>  	membarrier_arch_execve(t);
>  }
>  #else
> +#ifdef CONFIG_ARCH_HAS_MEMBARRIER_HOOKS
>  static inline void membarrier_arch_switch_mm(struct mm_struct *prev,
>  		struct mm_struct *next, struct task_struct *tsk)
>  {
>  }
> +#endif
>  static inline void membarrier_fork(struct task_struct *t,
>  		unsigned long clone_flags)
>  {
> -- 
> 2.11.0
>