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=-11.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,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 789FAC2D0A3 for ; Thu, 12 Nov 2020 09:28:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 35849221FF for ; Thu, 12 Nov 2020 09:28:07 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726843AbgKLJ2G (ORCPT ); Thu, 12 Nov 2020 04:28:06 -0500 Received: from foss.arm.com ([217.140.110.172]:45076 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725902AbgKLJ2F (ORCPT ); Thu, 12 Nov 2020 04:28:05 -0500 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 7BB8C1FB; Thu, 12 Nov 2020 01:28:04 -0800 (PST) Received: from [10.57.23.123] (unknown [10.57.23.123]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 38CD03F73C; Thu, 12 Nov 2020 01:28:03 -0800 (PST) Subject: Re: [RFC 09/11] coresight: etm-perf: Disable the path before capturing the trace data To: Anshuman Khandual , linux-arm-kernel@lists.infradead.org, coresight@lists.linaro.org Cc: linux-kernel@vger.kernel.org, mathieu.poirier@linaro.org, mike.leach@linaro.org References: <1605012309-24812-1-git-send-email-anshuman.khandual@arm.com> <1605012309-24812-10-git-send-email-anshuman.khandual@arm.com> From: Suzuki K Poulose Message-ID: <1ad992f4-5981-6ff1-470b-875e30d3c229@arm.com> Date: Thu, 12 Nov 2020 09:27:56 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.4.1 MIME-Version: 1.0 In-Reply-To: <1605012309-24812-10-git-send-email-anshuman.khandual@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 11/10/20 12:45 PM, Anshuman Khandual wrote: > perf handle structure needs to be shared with the TRBE IRQ handler for > capturing trace data and restarting the handle. There is a probability > of an undefined reference based crash when etm event is being stopped > while a TRBE IRQ also getting processed. This happens due the release > of perf handle via perf_aux_output_end(). This stops the sinks via the > link before releasing the handle, which will ensure that a simultaneous > TRBE IRQ could not happen. > > Signed-off-by: Anshuman Khandual > --- > This might cause problem with traditional sink devices which can be > operated in both sysfs and perf mode. This needs to be addressed > correctly. One option would be to move the update_buffer callback > into the respective sink devices. e.g, disable(). > > drivers/hwtracing/coresight/coresight-etm-perf.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/drivers/hwtracing/coresight/coresight-etm-perf.c b/drivers/hwtracing/coresight/coresight-etm-perf.c > index 534e205..1a37991 100644 > --- a/drivers/hwtracing/coresight/coresight-etm-perf.c > +++ b/drivers/hwtracing/coresight/coresight-etm-perf.c > @@ -429,7 +429,9 @@ static void etm_event_stop(struct perf_event *event, int mode) > > size = sink_ops(sink)->update_buffer(sink, handle, > event_data->snk_config); > + coresight_disable_path(path); > perf_aux_output_end(handle, size); > + return; > } As you mentioned, this is not ideal where another session could be triggered on the sink from a different ETM (not for per-CPU sink) in a different mode before you collect the buffer. I believe the best option is to leave the update_buffer() to disable_hw. This would need to pass on the "handle" to the disable_path. That way the races can be handled inside the sinks. Also, this aligns the perf mode of the sinks with that of the sysfs mode. Suzuki