linux-kernel - [PATCH v4 05/11] perf auxtrace: Use WRITE_ONCE() for updating aux

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Date:   Sun, 11 Jul 2021 18:40:59 +0800
From:   Leo Yan <leo.yan@...aro.org>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Borislav Petkov <bp@...en8.de>, x86@...nel.org,
        "H. Peter Anvin" <hpa@...or.com>,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Mike Leach <mike.leach@...aro.org>,
        linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
        coresight@...ts.linaro.org, linux-arm-kernel@...ts.infradead.org
Cc:     Leo Yan <leo.yan@...aro.org>
Subject: [PATCH v4 05/11] perf auxtrace: Use WRITE_ONCE() for updating aux_tail

Use WRITE_ONCE() for updating aux_tail, so can avoid unexpected memory
behaviour.

Signed-off-by: Leo Yan <leo.yan@...aro.org>
Acked-by: Adrian Hunter <adrian.hunter@...el.com>
Acked-by: Peter Zijlstra (Intel) <peterz@...radead.org>
---
 tools/perf/util/auxtrace.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/perf/util/auxtrace.h b/tools/perf/util/auxtrace.h
index cc1c1b9cec9c..79227b8864cd 100644
--- a/tools/perf/util/auxtrace.h
+++ b/tools/perf/util/auxtrace.h
@@ -480,7 +480,7 @@ static inline void auxtrace_mmap__write_tail(struct auxtrace_mmap *mm, u64 tail)
 	/* Ensure all reads are done before we write the tail out */
 	smp_mb();
 #if BITS_PER_LONG == 64 || !defined(HAVE_SYNC_COMPARE_AND_SWAP_SUPPORT)
-	pc->aux_tail = tail;
+	WRITE_ONCE(pc->aux_tail, tail);
 #else
 	do {
 		old_tail = __sync_val_compare_and_swap(&pc->aux_tail, 0, 0);
-- 
2.25.1