----- On Oct 20, 2020, at 10:36 AM, Peter Zijlstra peterz@xxxxxxxxxxxxx wrote:
> On Tue, Oct 20, 2020 at 09:47:13AM -0400, Mathieu Desnoyers wrote:
>> +void membarrier_update_current_mm(struct mm_struct *next_mm)
>> +{
>> + struct rq *rq = this_rq();
>> + int membarrier_state = 0;
>> +
>> + if (next_mm)
>> + membarrier_state = atomic_read(&next_mm->membarrier_state);
>> + if (READ_ONCE(rq->membarrier_state) == membarrier_state)
>> + return;
>> + WRITE_ONCE(rq->membarrier_state, membarrier_state);
>> +}
>
> This is suspisioucly similar to membarrier_switch_mm().
>
> Would something like so make sense?
Very much yes. Do you want me to re-send the series, or you
want to fold this in as you merge it ?
Thanks,
Mathieu
>
> ---
> --- a/kernel/sched/membarrier.c
> +++ b/kernel/sched/membarrier.c
> @@ -206,14 +206,7 @@ void membarrier_exec_mmap(struct mm_stru
>
> void membarrier_update_current_mm(struct mm_struct *next_mm)
> {
> - struct rq *rq = this_rq();
> - int membarrier_state = 0;
> -
> - if (next_mm)
> - membarrier_state = atomic_read(&next_mm->membarrier_state);
> - if (READ_ONCE(rq->membarrier_state) == membarrier_state)
> - return;
> - WRITE_ONCE(rq->membarrier_state, membarrier_state);
> + membarrier_switch_mm(this_rq(), NULL, next_mm);
> }
>
> static int membarrier_global_expedited(void)
> diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
> index d2621155393c..3d589c2ffd28 100644
> --- a/kernel/sched/sched.h
> +++ b/kernel/sched/sched.h
> @@ -2645,12 +2645,14 @@ static inline void membarrier_switch_mm(struct rq *rq,
> struct mm_struct *prev_mm,
> struct mm_struct *next_mm)
> {
> - int membarrier_state;
> + int membarrier_state = 0;
>
> if (prev_mm == next_mm)
> return;
>
> - membarrier_state = atomic_read(&next_mm->membarrier_state);
> + if (next_mm)
> + membarrier_state = atomic_read(&next_mm->membarrier_state);
> +
> if (READ_ONCE(rq->membarrier_state) == membarrier_state)
> return;
--
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com
