From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-18.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 57E0AC07E9C for ; Sun, 11 Jul 2021 10:41:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3FEBB610D2 for ; Sun, 11 Jul 2021 10:41:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232307AbhGKKoK (ORCPT ); Sun, 11 Jul 2021 06:44:10 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48458 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232213AbhGKKoG (ORCPT ); Sun, 11 Jul 2021 06:44:06 -0400 Received: from mail-pl1-x62a.google.com (mail-pl1-x62a.google.com [IPv6:2607:f8b0:4864:20::62a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B2308C0613E5 for ; Sun, 11 Jul 2021 03:41:19 -0700 (PDT) Received: by mail-pl1-x62a.google.com with SMTP id a14so7491411pls.4 for ; Sun, 11 Jul 2021 03:41:19 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=mUfdU9WBYmi8/NBmndyLWLFFhQ6mqBUwjCh/GuP5qb8=; b=RtX0qI4MGvgBvDGGTerEq7GxtH+wniuNEW7utX4Sj0O4q4Q26d6jcMwwestxzCiHzf QNREUyk2x12NqOorPsbS3FoidmVIpuT/X9x1hAaaDwk5vvIg5bJeUN/xIvP+5jXZxRNx u/oWY3EUWzmjc8kBz9+LguNLGpCx88gDP2zAl34xnTCTXim7dSVTNN4jzMPHY5CZfNP3 rQ+MsT5YTP5b2k71mOiwnmQObvk5ATNEF1tVHNUWlJA56zt5qd8az7VglCncXoOBA7Zf bgX5cPJFk47D0smGeeKZxFnYCvrVO30Dz7ypy3OlOpHsT0reQULiqgBvOOWyCoycLp+D xZDA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=mUfdU9WBYmi8/NBmndyLWLFFhQ6mqBUwjCh/GuP5qb8=; b=VyWnvEmGYq17iltXzcwWvaJkmcK4wkI2jLQFo6p7SlgRqMR3Y6JEg/LDrq3ISFKYNi xu8iO3yxX0sI5ZXRdfGbTi3O/ktdfTTlO6N1R/yok0sIR/FBgrMXSy6T3x0kCy4fMoSo lx2NeoXmeOE5fsN5wU3kdF8vYhEqHFIJqaU6IYC9mcZEkgY2BwHjaPOoWyYVM/SQxMUR ButfpRJvA0sb0SciClKUDN+knPSeJkJu0KBwN9weYVMgD15EnwDktq4S0VilROCAvvHN Zears/qrfjyxGjBerCZjA5MIWzYfoG0H2iNfwr08O02pbNzszOeYmvqlyMQ0+U+Kaf0M CvOg== X-Gm-Message-State: AOAM5333sr5fNwjewP+DCrMxgbU7oVxy2ej/JkWpHGbZZeslpkxsy18x D5xeV/WdANrWvdw91eV97R18vg== X-Google-Smtp-Source: ABdhPJyQ8XxCLn1vu+B0STHNwIFTAWH9uvWnYEj6A61rhx5yfvxHRMAmDfZWPGYHsUsY0F9uNVDSvg== X-Received: by 2002:a17:90a:9511:: with SMTP id t17mr48277859pjo.108.1626000079190; Sun, 11 Jul 2021 03:41:19 -0700 (PDT) Received: from localhost ([103.127.241.250]) by smtp.gmail.com with ESMTPSA id t2sm16735752pjq.0.2021.07.11.03.41.18 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 11 Jul 2021 03:41:18 -0700 (PDT) From: Leo Yan To: Arnaldo Carvalho de Melo , Adrian Hunter , Peter Zijlstra , Ingo Molnar , Mark Rutland , Alexander Shishkin , Jiri Olsa , Namhyung Kim , Thomas Gleixner , Borislav Petkov , x86@kernel.org, "H. Peter Anvin" , Mathieu Poirier , Suzuki K Poulose , Mike Leach , linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org, coresight@lists.linaro.org, linux-arm-kernel@lists.infradead.org Cc: Leo Yan 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 Message-Id: <20210711104105.505728-2-leo.yan@linaro.org> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20210711104105.505728-1-leo.yan@linaro.org> References: <20210711104105.505728-1-leo.yan@linaro.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.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 Acked-by: Peter Zijlstra (Intel) --- 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; 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Sun, 11 Jul 2021 03:41:18 -0700 (PDT) From: Leo Yan To: Arnaldo Carvalho de Melo , Adrian Hunter , Peter Zijlstra , Ingo Molnar , Mark Rutland , Alexander Shishkin , Jiri Olsa , Namhyung Kim , Thomas Gleixner , Borislav Petkov , x86@kernel.org, "H. Peter Anvin" , Mathieu Poirier , Suzuki K Poulose , Mike Leach , linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org, coresight@lists.linaro.org, linux-arm-kernel@lists.infradead.org Cc: Leo Yan 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 Message-Id: <20210711104105.505728-2-leo.yan@linaro.org> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20210711104105.505728-1-leo.yan@linaro.org> References: <20210711104105.505728-1-leo.yan@linaro.org> MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210711_034120_160951_D965B684 X-CRM114-Status: GOOD ( 15.46 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.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 Acked-by: Peter Zijlstra (Intel) --- 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