linux-kernel - [PATCH v5 4/9] perf/x86: Add compiler barrier after updating BTS

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Message-Id: <20210809111407.596077-5-leo.yan@linaro.org>
Date:   Mon,  9 Aug 2021 19:14:02 +0800
From:   Leo Yan <leo.yan@...aro.org>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Adrian Hunter <adrian.hunter@...el.com>,
        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>,
        "H. Peter Anvin" <hpa@...or.com>,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Mike Leach <mike.leach@...aro.org>,
        Michael Petlan <mpetlan@...hat.com>,
        "Frank Ch. Eigler" <fche@...hat.com>,
        Song Liu <songliubraving@...com>, x86@...nel.org,
        Daniel Díaz <daniel.diaz@...aro.org>,
        Andrii Nakryiko <andriin@...com>,
        Alexei Starovoitov <ast@...nel.org>,
        Sedat Dilek <sedat.dilek@...il.com>,
        Andi Kleen <ak@...ux.intel.com>,
        linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
        coresight@...ts.linaro.org
Cc:     Leo Yan <leo.yan@...aro.org>
Subject: [PATCH v5 4/9] perf/x86: Add compiler barrier after updating BTS

Since BTS is coherent, simply add a compiler barrier to separate the BTS
update and aux_head store.

Signed-off-by: Leo Yan <leo.yan@...aro.org>
---
 arch/x86/events/intel/bts.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/arch/x86/events/intel/bts.c b/arch/x86/events/intel/bts.c
index 6320d2cfd9d3..974e917e65b2 100644
--- a/arch/x86/events/intel/bts.c
+++ b/arch/x86/events/intel/bts.c
@@ -209,6 +209,12 @@ static void bts_update(struct bts_ctx *bts)
 	} else {
 		local_set(&buf->data_size, head);
 	}
+
+	/*
+	 * Since BTS is coherent, just add compiler barrier to ensure
+	 * BTS updating is ordered against bts::handle::event.
+	 */
+	barrier();
 }
 
 static int
-- 
2.25.1