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=-10.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,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 23EB7C433F5 for ; Wed, 22 Sep 2021 15:21:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0C5B2611CA for ; Wed, 22 Sep 2021 15:21:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236366AbhIVPWc (ORCPT ); Wed, 22 Sep 2021 11:22:32 -0400 Received: from foss.arm.com ([217.140.110.172]:50474 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236393AbhIVPW3 (ORCPT ); Wed, 22 Sep 2021 11:22:29 -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 71AB6113E; Wed, 22 Sep 2021 08:20:59 -0700 (PDT) Received: from [10.57.95.67] (unknown [10.57.95.67]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 46C8F3F718; Wed, 22 Sep 2021 08:20:58 -0700 (PDT) Subject: Re: [PATCH v2 1/1] coresight: Don't immediately close events that are run on invalid CPU/sink combos To: James Clark , mathieu.poirier@linaro.org, coresight@lists.linaro.org Cc: Mike Leach , Leo Yan , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org References: <20210922125144.133872-1-james.clark@arm.com> <20210922125144.133872-2-james.clark@arm.com> From: Suzuki K Poulose Message-ID: Date: Wed, 22 Sep 2021 16:20:56 +0100 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:78.0) Gecko/20100101 Thunderbird/78.14.0 MIME-Version: 1.0 In-Reply-To: <20210922125144.133872-2-james.clark@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 22/09/2021 13:51, James Clark wrote: > When a traced process runs on a CPU that can't reach the selected sink, > the event will be stopped with PERF_HES_STOPPED. This means that even if > the process migrates to a valid CPU, tracing will not resume. > > This can be reproduced (on N1SDP) by using taskset to start the process > on CPU 0, and then switching it to CPU 2 (ETF 1 is only reachable from > CPU 2): > > taskset --cpu-list 0 ./perf record -e cs_etm/@tmc_etf1/ --per-thread -- taskset --cpu-list 2 ls > > This produces a single 0 length AUX record, and then no more trace: > > 0x3c8 [0x30]: PERF_RECORD_AUX offset: 0 size: 0 flags: 0x1 [T] > > After the fix, the same command produces normal AUX records. The perf > self test "89: Check Arm CoreSight trace data recording and synthesized > samples" no longer fails intermittently. This was because the taskset in > the test is after the fork, so there is a period where the task is > scheduled on a random CPU rather than forced to a valid one. > > Specifically selecting an invalid CPU will still result in a failure to > open the event because it will never produce trace: > > ./perf record -C 2 -e cs_etm/@tmc_etf0/ > failed to mmap with 12 (Cannot allocate memory) > > The only scenario that has changed is if the CPU mask has a valid CPU > sink combo in it. > > Testing > ======= > > * Coresight self test passes consistently: > ./perf test Coresight > > * CPU wide mode still produces trace: > ./perf record -e cs_etm// -a > > * Invalid -C options still fail to open: > ./perf record -C 2,3 -e cs_etm/@tmc_etf0/ > failed to mmap with 12 (Cannot allocate memory) > > * Migrating a task to a valid sink/CPU now produces trace: > taskset --cpu-list 0 ./perf record -e cs_etm/@tmc_etf1/ --per-thread -- taskset --cpu-list 2 ls > > * If the task remains on an invalid CPU, no trace is emitted: > taskset --cpu-list 0 ./perf record -e cs_etm/@tmc_etf1/ --per-thread -- ls > > Reviewed-by: Mathieu Poirier > Reviewed-by: Suzuki K Poulose > Signed-off-by: James Clark Thanks James, I have queued this. Suzuki