From: Leo Yan <leo.yan@linaro.org> To: 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>, Suzuki K Poulose <suzuki.poulose@arm.com>, 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 Cc: Leo Yan <leo.yan@linaro.org> Subject: [PATCH v4 01/11] perf/ring_buffer: Add comment for barriers on AUX ring buffer Date: Sun, 11 Jul 2021 18:40:55 +0800 [thread overview] Message-ID: <20210711104105.505728-2-leo.yan@linaro.org> (raw) In-Reply-To: <20210711104105.505728-1-leo.yan@linaro.org> AUX ring buffer applies almost the same barriers as perf ring buffer, but there has an exception for ordering between writing the AUX trace data and updating user_page::aux_head. This patch adds comment for how to use the barriers on AUX ring buffer, and gives comment to ask the drivers to flush the trace data into AUX ring buffer prior to updating user_page::aux_head. Signed-off-by: Leo Yan <leo.yan@linaro.org> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> --- kernel/events/ring_buffer.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/kernel/events/ring_buffer.c b/kernel/events/ring_buffer.c index 52868716ec35..5cf6579be05e 100644 --- a/kernel/events/ring_buffer.c +++ b/kernel/events/ring_buffer.c @@ -509,6 +509,15 @@ void perf_aux_output_end(struct perf_output_handle *handle, unsigned long size) perf_event_aux_event(handle->event, aux_head, size, handle->aux_flags); + /* + * See perf_output_put_handle(), AUX ring buffer applies the same + * barrier pairing as the perf ring buffer; except for B, since + * AUX ring buffer is written by hardware trace, we cannot simply + * use the generic memory barrier (like smp_wmb()) prior to update + * user_page::aux_head, the hardware trace driver takes the + * responsibility to ensure the trace data has been flushed into + * the AUX buffer before calling perf_aux_output_end(). + */ WRITE_ONCE(rb->user_page->aux_head, rb->aux_head); if (rb_need_aux_wakeup(rb)) wakeup = true; -- 2.25.1
WARNING: multiple messages have this Message-ID (diff)
From: Leo Yan <leo.yan@linaro.org> To: 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>, Suzuki K Poulose <suzuki.poulose@arm.com>, 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 Cc: Leo Yan <leo.yan@linaro.org> Subject: [PATCH v4 01/11] perf/ring_buffer: Add comment for barriers on AUX ring buffer Date: Sun, 11 Jul 2021 18:40:55 +0800 [thread overview] Message-ID: <20210711104105.505728-2-leo.yan@linaro.org> (raw) In-Reply-To: <20210711104105.505728-1-leo.yan@linaro.org> AUX ring buffer applies almost the same barriers as perf ring buffer, but there has an exception for ordering between writing the AUX trace data and updating user_page::aux_head. This patch adds comment for how to use the barriers on AUX ring buffer, and gives comment to ask the drivers to flush the trace data into AUX ring buffer prior to updating user_page::aux_head. Signed-off-by: Leo Yan <leo.yan@linaro.org> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> --- kernel/events/ring_buffer.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/kernel/events/ring_buffer.c b/kernel/events/ring_buffer.c index 52868716ec35..5cf6579be05e 100644 --- a/kernel/events/ring_buffer.c +++ b/kernel/events/ring_buffer.c @@ -509,6 +509,15 @@ void perf_aux_output_end(struct perf_output_handle *handle, unsigned long size) perf_event_aux_event(handle->event, aux_head, size, handle->aux_flags); + /* + * See perf_output_put_handle(), AUX ring buffer applies the same + * barrier pairing as the perf ring buffer; except for B, since + * AUX ring buffer is written by hardware trace, we cannot simply + * use the generic memory barrier (like smp_wmb()) prior to update + * user_page::aux_head, the hardware trace driver takes the + * responsibility to ensure the trace data has been flushed into + * the AUX buffer before calling perf_aux_output_end(). + */ WRITE_ONCE(rb->user_page->aux_head, rb->aux_head); if (rb_need_aux_wakeup(rb)) wakeup = true; -- 2.25.1 _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next prev parent reply other threads:[~2021-07-11 10:41 UTC|newest] Thread overview: 68+ 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 ` Leo Yan 2021-07-11 10:40 ` Leo Yan [this message] 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 2021-07-11 10:40 ` Leo Yan 2021-07-12 10:40 ` Suzuki K Poulose 2021-07-12 10:40 ` Suzuki K Poulose 2021-07-12 10:54 ` Leo Yan 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 2021-07-11 10:40 ` Leo Yan 2021-07-13 12:56 ` Peter Zijlstra 2021-07-13 12:56 ` Peter Zijlstra 2021-07-13 15:49 ` Leo Yan 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 2021-07-11 10:40 ` Leo Yan 2021-07-13 13:01 ` Peter Zijlstra 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 10:40 ` Leo Yan 2021-07-11 10:41 ` [PATCH v4 06/11] perf auxtrace: Drop legacy __sync functions Leo Yan 2021-07-11 10:41 ` Leo Yan 2021-07-11 10:41 ` [PATCH v4 07/11] perf auxtrace: Remove auxtrace_mmap__read_snapshot_head() Leo Yan 2021-07-11 10:41 ` Leo Yan 2021-07-12 14:32 ` Adrian Hunter 2021-07-12 14:32 ` Adrian Hunter 2021-07-13 13:10 ` Leo Yan 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 ` 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 ` Leo Yan 2021-07-11 10:41 ` [PATCH v4 10/11] perf env: Set flag for kernel is 64-bit mode Leo Yan 2021-07-11 10:41 ` Leo Yan 2021-07-12 14:37 ` Adrian Hunter 2021-07-12 14:37 ` Adrian Hunter 2021-07-12 18:14 ` Arnaldo Carvalho de Melo 2021-07-12 18:14 ` Arnaldo Carvalho de Melo 2021-07-13 15:09 ` Leo Yan 2021-07-13 15:09 ` Leo Yan 2021-07-13 17:31 ` Hunter, Adrian 2021-07-13 17:31 ` Hunter, Adrian 2021-07-14 13:59 ` Arnaldo Carvalho de Melo 2021-07-14 13:59 ` Arnaldo Carvalho de Melo 2021-07-14 14:00 ` Arnaldo Carvalho de Melo 2021-07-14 14:00 ` Arnaldo Carvalho de Melo 2021-07-23 7:11 ` Leo Yan 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 2021-07-11 10:41 ` Leo Yan 2021-07-12 14:44 ` Russell King (Oracle) 2021-07-12 14:44 ` Russell King (Oracle) 2021-07-13 15:46 ` Leo Yan 2021-07-13 15:46 ` Leo Yan 2021-07-13 16:14 ` Russell King (Oracle) 2021-07-13 16:14 ` Russell King (Oracle) 2021-07-13 18:13 ` Catalin Marinas 2021-07-13 18:13 ` Catalin Marinas 2021-07-14 8:40 ` Russell King (Oracle) 2021-07-14 8:40 ` Russell King (Oracle) 2021-07-23 7:23 ` Leo Yan 2021-07-23 7:23 ` Leo Yan 2021-07-13 7:07 ` Adrian Hunter 2021-07-13 7:07 ` Adrian Hunter 2021-07-13 15:48 ` Leo Yan 2021-07-13 15:48 ` Leo Yan
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