linux-kernel - [PATCH v2 5/8] perf auxtrace: Change to use SMP memory barriers

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Date:   Wed,  2 Jun 2021 18:30:04 +0800
From:   Leo Yan <leo.yan@...aro.org>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        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>, 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>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Andi Kleen <ak@...ux.intel.com>,
        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 v2 5/8] perf auxtrace: Change to use SMP memory barriers

The kernel and the userspace tool can access the AUX ring buffer head
and tail from different CPUs, thus SMP class of barriers are required
on SMP system.

This patch changes to use SMP barriers to replace mb() and rmb()
barriers.

Signed-off-by: Leo Yan <leo.yan@...aro.org>
---
 tools/perf/util/auxtrace.h | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/tools/perf/util/auxtrace.h b/tools/perf/util/auxtrace.h
index a4fbb33b7245..42b7ef811bde 100644
--- a/tools/perf/util/auxtrace.h
+++ b/tools/perf/util/auxtrace.h
@@ -444,7 +444,7 @@ static inline u64 auxtrace_mmap__read_snapshot_head(struct auxtrace_mmap *mm)
 	u64 head = READ_ONCE(pc->aux_head);
 
 	/* Ensure all reads are done after we read the head */
-	rmb();
+	smp_rmb();
 	return head;
 }
 
@@ -458,7 +458,7 @@ static inline u64 auxtrace_mmap__read_head(struct auxtrace_mmap *mm)
 #endif
 
 	/* Ensure all reads are done after we read the head */
-	rmb();
+	smp_rmb();
 	return head;
 }
 
@@ -470,7 +470,7 @@ static inline void auxtrace_mmap__write_tail(struct auxtrace_mmap *mm, u64 tail)
 #endif
 
 	/* Ensure all reads are done before we write the tail out */
-	mb();
+	smp_mb();
 #if BITS_PER_LONG == 64 || !defined(HAVE_SYNC_COMPARE_AND_SWAP_SUPPORT)
 	pc->aux_tail = tail;
 #else
-- 
2.25.1