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

From: Mathieu Desnoyers <[email-masked]>
Date: Fri, 6 Oct 2017 21:53:33 +0000 (UTC)

----- On Oct 6, 2017, at 5:08 PM, Paul E. McKenney [email-masked] wrote:

> 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.

Hi Paul,

Given that the following patch in this patchset (2/2)
"Fix: membarrier: Handle CLONE_VM + !CLONE_THREAD correctly on powerpc"
is based on this patch, and that the fix needs to go into 4.14,
I would recommend queuing both patches for 4.14 is possible.

Otherwise I could try swapping the order of the two patches if
needed, but since both are touching nearby code areas, rebasing
is not straightforward.

Thanks,

Mathieu

> 
>							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

-- 
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com