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 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 0C2E5C36010 for ; Tue, 1 Apr 2025 13:00:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: Content-Type:In-Reply-To:From:References:To:Subject:MIME-Version:Date: Message-ID:Reply-To:Cc:Content-ID:Content-Description:Resent-Date:Resent-From :Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=Dp7BPKuB4zCs/+3PHXfcxNLJlisKEZ/RDTpAdSVNhe0=; b=OQi1Ir5rMcOWa8rZVtRf0l8XMX +SoFa5iTB8F2uEDO20UDugY3620voeNeAS9YVFoKrqsR86H1mnTTBrszZmhvrju17MjGxazvrM2cn 6o7sQkuGw9gvcdZQwaPxq4SSokftpVuyKFXybZKtN9zt0faev0elo4T1YXm2gm3HHeG5AuCIYsGsr ZvH5cSIYG3FUZ7fP7ZYDi0LX+JLF2Zn3p5bz3e9sZF9VzdoKo7FcfZZYx2T1P1R5hvEhZS3l5MhHF CrwtfaWNv/L1MJwizIkAFPGKIsTleNLtsUQn59TYvTT4zzftmeW3EIYfSDK7CIWaxcgKk1XMv0BGJ h9tWh84A==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.1 #2 (Red Hat Linux)) id 1tzbEJ-00000003NQm-31ih; Tue, 01 Apr 2025 13:00:35 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.98.1 #2 (Red Hat Linux)) id 1tzb6P-00000003MFi-1c3i for linux-arm-kernel@lists.infradead.org; Tue, 01 Apr 2025 12:52:26 +0000 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 ED76A14BF; Tue, 1 Apr 2025 05:52:25 -0700 (PDT) Received: from [10.1.197.1] (ewhatever.cambridge.arm.com [10.1.197.1]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 8E0933F694; Tue, 1 Apr 2025 05:52:21 -0700 (PDT) Message-ID: <8d9ad64b-a5f7-4a44-a557-7edb83322fdf@arm.com> Date: Tue, 1 Apr 2025 13:51:36 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 5/6] coresight: perf: Update buffer on AUX pause To: Leo Yan , Mike Leach , James Clark , Jonathan Corbet , Alexander Shishkin , coresight@lists.linaro.org, linux-arm-kernel@lists.infradead.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org References: <20250311170451.611389-1-leo.yan@arm.com> <20250311170451.611389-6-leo.yan@arm.com> Content-Language: en-US From: Suzuki K Poulose In-Reply-To: <20250311170451.611389-6-leo.yan@arm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250401_055225_525714_6DF46737 X-CRM114-Status: GOOD ( 24.89 ) 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: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 11/03/2025 17:04, Leo Yan wrote: > Due to sinks like ETR and ETB don't support interrupt handling, the > hardware trace data might be lost for continuous running tasks. > > This commit takes advantage of the AUX pause for updating trace buffer > to mitigate the trace data losing issue. > > The per CPU sink has its own interrupt handling. Thus, there will be a > race condition between the updating buffer in NMI and sink's interrupt > handler. To avoid the race condition, this commit disallows updating > buffer on AUX pause for the per CPU sink. Currently, this is only > applied for TRBE. > > Signed-off-by: Leo Yan > --- > .../hwtracing/coresight/coresight-etm-perf.c | 43 ++++++++++++++++++- > 1 file changed, 41 insertions(+), 2 deletions(-) > > diff --git a/drivers/hwtracing/coresight/coresight-etm-perf.c b/drivers/hwtracing/coresight/coresight-etm-perf.c > index 2dcf1809cb7f..f1551c08ecb2 100644 > --- a/drivers/hwtracing/coresight/coresight-etm-perf.c > +++ b/drivers/hwtracing/coresight/coresight-etm-perf.c > @@ -574,14 +574,53 @@ static void etm_event_start(struct perf_event *event, int flags) > return; > } > > -static void etm_event_pause(struct coresight_device *csdev, > +static void etm_event_pause(struct perf_event *event, > + struct coresight_device *csdev, > struct etm_ctxt *ctxt) > { > + int cpu = smp_processor_id(); > + struct coresight_device *sink; > + struct perf_output_handle *handle = &ctxt->handle; > + struct coresight_path *path; > + unsigned long size; > + > if (!ctxt->event_data) > return; > > /* Stop tracer */ > coresight_pause_source(csdev); > + > + path = etm_event_cpu_path(ctxt->event_data, cpu); > + sink = coresight_get_sink(path); > + if (WARN_ON_ONCE(!sink)) > + return; > + > + /* > + * The per CPU sink has own interrupt handling, it might have > + * race condition with updating buffer on AUX trace pause if > + * it is invoked from NMI. To avoid the race condition, > + * disallows updating buffer for the per CPU sink case. > + */ > + if (coresight_is_percpu_sink(sink)) > + return; > + > + if (WARN_ON_ONCE(handle->event != event)) > + return; > + > + if (!sink_ops(sink)->update_buffer) > + return; > + > + size = sink_ops(sink)->update_buffer(sink, handle, > + ctxt->event_data->snk_config); I believe we keep the sink disabled/stopped in update_buffer. We need to turn it back ON after the "buffer update". May be we could use a flag to update_buffer() to indicate this is "pause" triggered update. Cheers Suzuki > + if (READ_ONCE(handle->event)) { > + if (!size) > + return; > + > + perf_aux_output_end(handle, size); > + perf_aux_output_begin(handle, event); > + } else { > + WARN_ON_ONCE(size); > + } > } > > static void etm_event_stop(struct perf_event *event, int mode) > @@ -595,7 +634,7 @@ static void etm_event_stop(struct perf_event *event, int mode) > struct coresight_path *path; > > if (mode & PERF_EF_PAUSE) > - return etm_event_pause(csdev, ctxt); > + return etm_event_pause(event, csdev, ctxt); > > /* > * If we still have access to the event_data via handle,