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

[Paul E. McKenney]

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 <npiggin@xxxxxxxxx>
> Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx>

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

							Thanx, Paul

> CC: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> CC: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
> CC: Boqun Feng <boqun.feng@xxxxxxxxx>
> CC: Andrew Hunter <ahh@xxxxxxxxxx>
> CC: Maged Michael <maged.michael@xxxxxxxxx>
> CC: gromer@xxxxxxxxxx
> CC: Avi Kivity <avi@xxxxxxxxxxxx>
> CC: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx>
> CC: Paul Mackerras <paulus@xxxxxxxxx>
> CC: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
> CC: Dave Watson <davejwatson@xxxxxx>
> CC: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>
> CC: Will Deacon <will.deacon@xxxxxxx>
> CC: Andy Lutomirski <luto@xxxxxxxxxx>
> CC: Ingo Molnar <mingo@xxxxxxxxxx>
> CC: Alexander Viro <viro@xxxxxxxxxxxxxxxxxx>
> CC: linuxppc-dev@xxxxxxxxxxxxxxxx
> CC: linux-arch@xxxxxxxxxxxxxxx
> ---
>  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
>