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From: Leo Yan <leo.yan@linaro.org>
To: "Arnaldo Carvalho de Melo" <acme@kernel.org>,
	"Peter Zijlstra" <peterz@infradead.org>,
	"Adrian Hunter" <adrian.hunter@intel.com>,
	"Ingo Molnar" <mingo@redhat.com>,
	"Mark Rutland" <mark.rutland@arm.com>,
	"Alexander Shishkin" <alexander.shishkin@linux.intel.com>,
	"Jiri Olsa" <jolsa@redhat.com>,
	"Namhyung Kim" <namhyung@kernel.org>,
	"Thomas Gleixner" <tglx@linutronix.de>,
	"Borislav Petkov" <bp@alien8.de>,
	"H. Peter Anvin" <hpa@zytor.com>,
	"Mathieu Poirier" <mathieu.poirier@linaro.org>,
	"Suzuki K Poulose" <suzuki.poulose@arm.com>,
	"Mike Leach" <mike.leach@linaro.org>,
	"Michael Petlan" <mpetlan@redhat.com>,
	"Frank Ch. Eigler" <fche@redhat.com>,
	"Song Liu" <songliubraving@fb.com>,
	x86@kernel.org, "Daniel Díaz" <daniel.diaz@linaro.org>,
	"Andrii Nakryiko" <andriin@fb.com>,
	"Alexei Starovoitov" <ast@kernel.org>,
	"Sedat Dilek" <sedat.dilek@gmail.com>,
	"Andi Kleen" <ak@linux.intel.com>,
	linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org,
	coresight@lists.linaro.org
Cc: Leo Yan <leo.yan@linaro.org>
Subject: [PATCH v5 2/9] coresight: tmc-etr: Add barrier after updating AUX ring buffer
Date: Mon,  9 Aug 2021 19:14:00 +0800	[thread overview]
Message-ID: <20210809111407.596077-3-leo.yan@linaro.org> (raw)
In-Reply-To: <20210809111407.596077-1-leo.yan@linaro.org>

Since a memory barrier is required between AUX trace data store and
aux_head store, and the AUX trace data is filled with memcpy(), it's
sufficient to use smp_wmb() so can ensure the trace data is visible
prior to updating aux_head.

Signed-off-by: Leo Yan <leo.yan@linaro.org>
Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>
---
 drivers/hwtracing/coresight/coresight-tmc-etr.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/hwtracing/coresight/coresight-tmc-etr.c b/drivers/hwtracing/coresight/coresight-tmc-etr.c
index acdb59e0e661..13fd1fc730ed 100644
--- a/drivers/hwtracing/coresight/coresight-tmc-etr.c
+++ b/drivers/hwtracing/coresight/coresight-tmc-etr.c
@@ -1563,6 +1563,14 @@ tmc_update_etr_buffer(struct coresight_device *csdev,
 	 */
 	if (etr_perf->snapshot)
 		handle->head += size;
+
+	/*
+	 * Ensure that the AUX trace data is visible before the aux_head
+	 * is updated via perf_aux_output_end(), as expected by the
+	 * perf ring buffer.
+	 */
+	smp_wmb();
+
 out:
 	/*
 	 * Don't set the TRUNCATED flag in snapshot mode because 1) the
-- 
2.25.1


  parent reply	other threads:[~2021-08-09 11:15 UTC|newest]

Thread overview: 24+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-09 11:13 [PATCH v5 0/9] perf: Refine barriers for AUX ring buffer Leo Yan
2021-08-09 11:13 ` [PATCH v5 1/9] perf/ring_buffer: Add comment for barriers on " Leo Yan
2021-08-29 10:51   ` Leo Yan
2021-08-09 11:14 ` Leo Yan [this message]
2021-08-29 10:55   ` [PATCH v5 2/9] coresight: tmc-etr: Add barrier after updating " Leo Yan
2021-09-14  9:08     ` Suzuki K Poulose
2021-08-09 11:14 ` [PATCH v5 3/9] coresight: tmc-etf: Add comment for store ordering Leo Yan
2021-09-14  8:24   ` Suzuki K Poulose
2021-08-09 11:14 ` [PATCH v5 4/9] perf/x86: Add compiler barrier after updating BTS Leo Yan
2021-08-29 10:56   ` Leo Yan
2021-09-14  9:51     ` Peter Zijlstra
2021-09-14 10:05       ` Leo Yan
2021-09-14 11:47         ` Peter Zijlstra
2021-09-17 15:10   ` [tip: perf/core] " tip-bot2 for Leo Yan
2021-08-09 11:14 ` [PATCH v5 5/9] perf auxtrace: Use WRITE_ONCE() for updating aux_tail Leo Yan
2021-08-09 19:59   ` Arnaldo Carvalho de Melo
2021-08-09 11:14 ` [PATCH v5 6/9] perf auxtrace: Drop legacy __sync functions Leo Yan
2021-08-09 20:00   ` Arnaldo Carvalho de Melo
2021-08-09 11:14 ` [PATCH v5 7/9] perf auxtrace: Remove auxtrace_mmap__read_snapshot_head() Leo Yan
2021-08-09 20:01   ` Arnaldo Carvalho de Melo
2021-08-09 11:14 ` [PATCH v5 8/9] perf: Cleanup for HAVE_SYNC_COMPARE_AND_SWAP_SUPPORT Leo Yan
2021-08-09 20:02   ` Arnaldo Carvalho de Melo
2021-08-09 11:14 ` [PATCH v5 9/9] tools: Remove feature-sync-compare-and-swap feature detection Leo Yan
2021-08-09 20:02   ` Arnaldo Carvalho de Melo

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