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=-15.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham 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 D4997C07E96 for ; Thu, 15 Jul 2021 08:33:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id AD1C86127C for ; Thu, 15 Jul 2021 08:33:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240255AbhGOIgq (ORCPT ); Thu, 15 Jul 2021 04:36:46 -0400 Received: from foss.arm.com ([217.140.110.172]:48852 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229620AbhGOIgp (ORCPT ); Thu, 15 Jul 2021 04:36:45 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id C9ADDD6E; Thu, 15 Jul 2021 01:33:52 -0700 (PDT) Received: from [10.57.33.248] (unknown [10.57.33.248]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 10EDF3F774; Thu, 15 Jul 2021 01:33:50 -0700 (PDT) Subject: Re: [PATCH 4/5] coresight: trbe: Move irq_work queue processing To: Anshuman Khandual , linux-arm-kernel@lists.infradead.org Cc: coresight@lists.linaro.org, linux-kernel@vger.kernel.org, al.grant@arm.com, leo.yan@linaro.org, mathieu.poirier@linaro.org, mike.leach@linaro.org, peterz@infradead.org, Tamas.Zsoldos@arm.com, will@kernel.org References: <20210712113830.2803257-1-suzuki.poulose@arm.com> <20210712113830.2803257-5-suzuki.poulose@arm.com> <390617ae-c5bd-b73a-c48c-e62b7f5330ca@arm.com> From: Suzuki K Poulose Message-ID: Date: Thu, 15 Jul 2021 09:33:49 +0100 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 MIME-Version: 1.0 In-Reply-To: <390617ae-c5bd-b73a-c48c-e62b7f5330ca@arm.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-GB Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 15/07/2021 04:23, Anshuman Khandual wrote: > > > On 7/12/21 5:08 PM, Suzuki K Poulose wrote: >> The TRBE driver issues the irq_work_run() to ensure that >> any pending disable event callback has been processed. But this >> is done before we mark the AUX buffer as TRUNCATED, making >> the call pointless. Move the call after the current handle >> has been closed. > > So there is a possibility that a disable event gets missed before > the buffer is marked TRUNCATED ? But even then would not another No, it is the other way around. A disable event is triggered in response to the TRUNCATED flag. > disable event be triggered again subsequently ? Just trying to > understand what is the actual problem because of the current > placement of irq_work_run() ? That begs the question, What is the purpose of irq_work_run() ? See below. > >> >> Fixes: 3fbf7f011f24 ("coresight: sink: Add TRBE driver") >> Reported-by: Tamas Zsoldos >> Cc: Anshuman Khandual >> Cc: Mathieu Poirier >> Cc: Mike Leach >> Cc: Peter Zijlstra (Intel) >> Cc: Leo Yan >> Cc: Will Deacon >> Signed-off-by: Suzuki K Poulose >> --- >> drivers/hwtracing/coresight/coresight-trbe.c | 14 ++++++++------ >> 1 file changed, 8 insertions(+), 6 deletions(-) >> >> diff --git a/drivers/hwtracing/coresight/coresight-trbe.c b/drivers/hwtracing/coresight/coresight-trbe.c >> index ec38cf17b693..c0c264264427 100644 >> --- a/drivers/hwtracing/coresight/coresight-trbe.c >> +++ b/drivers/hwtracing/coresight/coresight-trbe.c >> @@ -723,6 +723,14 @@ static void trbe_handle_overflow(struct perf_output_handle *handle) >> perf_aux_output_flag(handle, PERF_AUX_FLAG_CORESIGHT_FORMAT_RAW | >> PERF_AUX_FLAG_TRUNCATED); >> perf_aux_output_end(handle, size); >> + >> + /* >> + * Ensure perf callbacks have completed. Since we >> + * always TRUNCATE the buffer on IRQ, the event >> + * is scheduled to be disabled. Make sure that happens >> + * as soon as possible. >> + */ >> + irq_work_run(); >> } >> >> static bool is_perf_trbe(struct perf_output_handle *handle) >> @@ -777,12 +785,6 @@ static irqreturn_t arm_trbe_irq_handler(int irq, void *dev) >> if (!is_perf_trbe(handle)) >> return IRQ_NONE; >> >> - /* >> - * Ensure perf callbacks have completed, which may disable >> - * the trace buffer in response to a TRUNCATION flag. >> - */ This comment here explains what the irq_work_run() is supposed to do. This clearly indicates that the event will be disabled in response to TRUNCATION. Now, we haven't updated the buffer flags yet here. It happens *after* this call, in handle_overflow(). So, this is placed incorrectly. The purpose of this patch is to make sure that we actually complete the callbacks in response to the TRUNCATED flag we set with this IRQ. >> - irq_work_run(); >> - >> act = trbe_get_fault_act(status); >> switch (act) { >> case TRBE_FAULT_ACT_WRAP: >> Suzuki