From: Suzuki K Poulose <suzuki.poulose@arm.com>
To: Leo Yan <leo.yan@linaro.org>,
Arnaldo Carvalho de Melo <acme@kernel.org>,
Adrian Hunter <adrian.hunter@intel.com>,
Peter Zijlstra <peterz@infradead.org>,
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>,
x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
Mathieu Poirier <mathieu.poirier@linaro.org>,
Mike Leach <mike.leach@linaro.org>,
linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org,
coresight@lists.linaro.org, linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v4 02/11] coresight: tmc-etr: Add barrier after updating AUX ring buffer
Date: Mon, 12 Jul 2021 11:40:12 +0100 [thread overview]
Message-ID: <f9734d69-b1f5-825c-f152-705626f4b256@arm.com> (raw)
In-Reply-To: <20210711104105.505728-3-leo.yan@linaro.org>
On 11/07/2021 11:40, Leo Yan wrote:
> 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>
> ---
> 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..713205db15a1 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;
> +
> + /*
> + * It requires the ordering between the AUX trace data and aux_head
> + * store, below smp_wmb() ensures the AUX trace data is visible prior
> + * to updating aux_head.
> + */
Please could we reword this a bit, something like :
/*
* 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();
> +
Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>
next prev parent reply other threads:[~2021-07-12 10:40 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-11 10:40 [PATCH v4 00/11] perf: Refine barriers for AUX ring buffer Leo Yan
2021-07-11 10:40 ` [PATCH v4 01/11] perf/ring_buffer: Add comment for barriers on " Leo Yan
2021-07-11 10:40 ` [PATCH v4 02/11] coresight: tmc-etr: Add barrier after updating " Leo Yan
2021-07-12 10:40 ` Suzuki K Poulose [this message]
2021-07-12 10:54 ` Leo Yan
2021-07-11 10:40 ` [PATCH v4 03/11] coresight: tmc-etf: Add comment for store ordering Leo Yan
2021-07-13 12:56 ` Peter Zijlstra
2021-07-13 15:49 ` Leo Yan
2021-07-11 10:40 ` [PATCH v4 04/11] perf/x86: Add barrier after updating bts Leo Yan
2021-07-13 13:01 ` Peter Zijlstra
2021-07-11 10:40 ` [PATCH v4 05/11] perf auxtrace: Use WRITE_ONCE() for updating aux_tail Leo Yan
2021-07-11 10:41 ` [PATCH v4 06/11] perf auxtrace: Drop legacy __sync functions Leo Yan
2021-07-11 10:41 ` [PATCH v4 07/11] perf auxtrace: Remove auxtrace_mmap__read_snapshot_head() Leo Yan
2021-07-12 14:32 ` Adrian Hunter
2021-07-13 13:10 ` Leo Yan
2021-07-11 10:41 ` [PATCH v4 08/11] perf: Cleanup for HAVE_SYNC_COMPARE_AND_SWAP_SUPPORT Leo Yan
2021-07-11 10:41 ` [PATCH v4 09/11] tools: Remove feature-sync-compare-and-swap feature detection Leo Yan
2021-07-11 10:41 ` [PATCH v4 10/11] perf env: Set flag for kernel is 64-bit mode Leo Yan
2021-07-12 14:37 ` Adrian Hunter
2021-07-12 18:14 ` Arnaldo Carvalho de Melo
2021-07-13 15:09 ` Leo Yan
2021-07-13 17:31 ` Hunter, Adrian
2021-07-14 13:59 ` Arnaldo Carvalho de Melo
2021-07-14 14:00 ` Arnaldo Carvalho de Melo
2021-07-23 7:11 ` Leo Yan
2021-07-11 10:41 ` [PATCH v4 11/11] perf auxtrace: Add compat_auxtrace_mmap__{read_head|write_tail} Leo Yan
2021-07-12 14:44 ` Russell King (Oracle)
2021-07-13 15:46 ` Leo Yan
2021-07-13 16:14 ` Russell King (Oracle)
2021-07-13 18:13 ` Catalin Marinas
2021-07-14 8:40 ` Russell King (Oracle)
2021-07-23 7:23 ` Leo Yan
2021-07-13 7:07 ` Adrian Hunter
2021-07-13 15:48 ` Leo Yan
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