On Wed, Oct 17, 2018 at 04:41:55PM +0200, Daniel Borkmann wrote:
> @@ -73,7 +73,8 @@ static inline u64 perf_mmap__read_head(struct perf_mmap *mm)
> {
> struct perf_event_mmap_page *pc = mm->base;
> u64 head = READ_ONCE(pc->data_head);
> - rmb();
> +
> + smp_rmb();
> return head;
> }
>
> @@ -84,7 +85,7 @@ static inline void perf_mmap__write_tail(struct perf_mmap
> *md, u64 tail)
> /*
> * ensure all reads are done before we write the tail out.
> */
> - mb();
> + smp_mb();
> pc->data_tail = tail;
Ideally that would be a WRITE_ONCE() to avoid store tearing.
Alternatively, I think we can use smp_store_release() here, all we care
about is that the prior loads stay prior.
Similarly, I suppose, we could use smp_load_acquire() for the data_head
load above.
> }
>
> --
> 2.9.5
>
