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SubjectRe: [PATCH] perf mmap: Convert ACCESS_ONCE() to READ_ONCE()
On Tue, Nov 14, 2017 at 10:31:38AM +0000, Mark Rutland wrote:
> Recently there was a treewide conversion of ACCESS_ONCE() to
> {READ,WRITE}_ONCE(), but a new use was introduced concurrently by
> commit:
>
> 1695849735752d2a ("perf mmap: Move perf_mmap and methods to separate mmap.[ch] files")
>
> Let's convert this over to READ_ONCE() so that we can remove the
> ACCESS_ONCE() definitions in subsequent patches.
>
> Signed-off-by: Mark Rutland <mark.rutland@arm.com>
> Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
> Cc: Ingo Molnar <mingo@redhat.com>
> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
> Cc: Peter Zijlstra <peterz@infradead.org>

Reviewed-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

Woo-hoo! Good to see that your Coccinelle script has already done
its magic! ;-)

Thanx, Paul

> ---
> tools/perf/util/mmap.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> Hi,
>
> Would it be possible for this to be taken as a fixup in an upcoming rc? That
> way we should be able to remove the ACCESS_ONCE() definitions prior to v4.15.
>
> Thanks,
> Mark.
>
> diff --git a/tools/perf/util/mmap.h b/tools/perf/util/mmap.h
> index efd78b827b05..3a5cb5a6e94a 100644
> --- a/tools/perf/util/mmap.h
> +++ b/tools/perf/util/mmap.h
> @@ -70,7 +70,7 @@ void perf_mmap__read_catchup(struct perf_mmap *md);
> static inline u64 perf_mmap__read_head(struct perf_mmap *mm)
> {
> struct perf_event_mmap_page *pc = mm->base;
> - u64 head = ACCESS_ONCE(pc->data_head);
> + u64 head = READ_ONCE(pc->data_head);
> rmb();
> return head;
> }
> --
> 2.11.0
>

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