[tip:locking/urgent] tools/perf: Convert ACCESS_ONCE() to READ_ONCE()

[tip-bot for Mark Rutland]

Commit-ID:  f971e511cb7d6f1b3730248cf2967d3ccdd8874c
Gitweb:     https://git.kernel.org/tip/f971e511cb7d6f1b3730248cf2967d3ccdd8874c
Author:     Mark Rutland <mark.rutland@xxxxxxx>
AuthorDate: Mon, 27 Nov 2017 10:38:21 +0000
Committer:  Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Tue, 12 Dec 2017 13:22:09 +0100

tools/perf: Convert ACCESS_ONCE() to READ_ONCE()

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.

Tested-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Mark Rutland <mark.rutland@xxxxxxx>
Reviewed-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
Cc: Joe Perches <joe@xxxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: apw@xxxxxxxxxxxxx
Link: http://lkml.kernel.org/r/20171127103824.36526-2-mark.rutland@xxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
 tools/perf/util/mmap.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/perf/util/mmap.h b/tools/perf/util/mmap.h
index efd78b8..3a5cb5a 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;
 }