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_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 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 6264EC433ED for ; Thu, 13 May 2021 13:10:57 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2A7926142E for ; Thu, 13 May 2021 13:10:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233740AbhEMNME (ORCPT ); Thu, 13 May 2021 09:12:04 -0400 Received: from foss.arm.com ([217.140.110.172]:35242 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230498AbhEMNMA (ORCPT ); Thu, 13 May 2021 09:12:00 -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 ED629ED1; Thu, 13 May 2021 06:10:50 -0700 (PDT) Received: from [10.57.81.122] (unknown [10.57.81.122]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 665753F73B; Thu, 13 May 2021 06:10:48 -0700 (PDT) Subject: Re: [RFC PATCH] perf cs-etm: Handle valid-but-zero timestamps To: Leo Yan Cc: coresight@lists.linaro.org, mathieu.poirier@linaro.org, al.grant@arm.com, branislav.rankov@arm.com, denik@chromium.org, suzuki.poulose@arm.com, anshuman.khandual@arm.com, Mike Leach , Mark Rutland , Alexander Shishkin , Jiri Olsa , Namhyung Kim , John Garry , Will Deacon , linux-arm-kernel@lists.infradead.org, linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org References: <20210507095814.17933-1-james.clark@arm.com> <3926c523-3fdb-66de-8b9c-b68290a5053e@arm.com> <20210510053904.GB4835@leoy-ThinkPad-X240s> <20210512020826.GC249068@leoy-ThinkPad-X240s> From: James Clark Message-ID: <347cb510-0057-4687-5b29-22568d228b7a@arm.com> Date: Thu, 13 May 2021 16:10:47 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <20210512020826.GC249068@leoy-ThinkPad-X240s> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 12/05/2021 05:08, Leo Yan wrote: > On Tue, May 11, 2021 at 04:53:35PM +0300, James Clark wrote: > > [...] > >> /* First get the packet queue for this traceID */ >> packet_queue = cs_etm__etmq_get_packet_queue(etmq, trace_chan_id); >> @@ -320,7 +323,20 @@ cs_etm_decoder__do_hard_timestamp(struct cs_etm_queue *etmq, >> * which instructions started by subtracting the number of instructions >> * executed to the timestamp. >> */ >> - packet_queue->timestamp = elem->timestamp - packet_queue->instr_count; >> + if (!elem->timestamp) { >> + packet_queue->timestamp = 0; >> + if (!warned_timestamp_zero) { >> + pr_err("Zero Coresight timestamp found at Idx:%" OCSD_TRC_IDX_STR >> + ". Decoding may be improved with --itrace=Z...\n", indx); >> + warned_timestamp_zero = true; >> + } >> + } >> + else if (packet_queue->instr_count >= elem->timestamp) { > > Nitpick: I personally think should use the condition ">" rather than ">=". Yes, good catch. I actually changed this because I realised that if they are equal it shouldn't print an error. > >> + packet_queue->timestamp = 0; >> + pr_err("Timestamp calculation underflow at Idx:%" OCSD_TRC_IDX_STR "\n", indx); >> + } >> + else >> + packet_queue->timestamp = elem->timestamp - packet_queue->instr_count; > > Nitpick for coding style, as described in > Documentation/process/coding-style.rst, section "3) Placing Braces and > Spaces", so here should use braces with the format: Ok I will update and run it through checkpatch.pl before posting. [...]