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=-16.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT 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 B2A90C07E9C for ; Mon, 12 Jul 2021 11:38:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 98B9661108 for ; Mon, 12 Jul 2021 11:38:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234581AbhGLLll (ORCPT ); Mon, 12 Jul 2021 07:41:41 -0400 Received: from foss.arm.com ([217.140.110.172]:54004 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234504AbhGLLli (ORCPT ); Mon, 12 Jul 2021 07:41:38 -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 082726D; Mon, 12 Jul 2021 04:38:50 -0700 (PDT) Received: from ewhatever.cambridge.arm.com (ewhatever.cambridge.arm.com [10.1.197.1]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id 764D13F694; Mon, 12 Jul 2021 04:38:48 -0700 (PDT) From: Suzuki K Poulose To: linux-arm-kernel@lists.infradead.org Cc: coresight@lists.linaro.org, linux-kernel@vger.kernel.org, al.grant@arm.com, anshuman.khandual@arm.com, leo.yan@linaro.org, mathieu.poirier@linaro.org, mike.leach@linaro.org, peterz@infradead.org, suzuki.poulose@arm.com, Tamas.Zsoldos@arm.com, will@kernel.org Subject: [PATCH 3/5] coresight: trbe: Keep TRBE disabled on overflow irq Date: Mon, 12 Jul 2021 12:38:28 +0100 Message-Id: <20210712113830.2803257-4-suzuki.poulose@arm.com> X-Mailer: git-send-email 2.24.1 In-Reply-To: <20210712113830.2803257-1-suzuki.poulose@arm.com> References: <20210712113830.2803257-1-suzuki.poulose@arm.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org When an AUX buffer is marked TRUNCATED, the kernel will disable the event (via irq_work) and can only be re-enabled by the userspace tool. Also, since we *always* mark the buffer as TRUNCATED (which is needs to be reconsidered, see below), we need not re-enable the TRBE as the event is going to be now disabled. This follows the SPE driver behavior. Without this change, we could leave the event disabled for ever under certain conditions. i.e, when we try to re-enable in the IRQ handler, if there is no space left in the buffer, we "TRUNCATE" the buffer and create a record of size 0. The perf tool skips such records and the event will remain disabled forever. Regarding the use of TRUNCATED flag: With FILL mode, the TRBE stops collection when the buffer is full, raising the IRQ. Now, since the IRQ is asynchronous, we could loose some amount of trace, after the buffer was full until the IRQ is handled. Also the last packet may have been trimmed. The decoder can figure this out and cope with this. The side effect of this approach is: We always disable the event when there is an IRQ, even when the other half of the ring buffer is free ! This is not ideal. Now, we should switch to using PARTIAL to indicate that there was potentially some partial trace packets in the buffer and some data was lost. We should use TRUNCATED only when there is absolutely no space in the ring buffer. This change would also require some additional changes in the CoreSight PMU framework to allow, sinks to "close" the handle (rather than the PMU driver closing the handle upon event_stop). So, until that is sorted, let us keep the TRUNCATED flag and the rework can be addressed separately. Fixes: 3fbf7f011f24 ("coresight: sink: Add TRBE driver") Reported-by: Tamas Zsoldos Cc: Anshuman Khandual Cc: Mathieu Poirier Cc: Mike Leach Cc: Leo Yan Cc: Peter Zijlstra (Intel) Cc: Will Deacon Signed-off-by: Suzuki K Poulose --- drivers/hwtracing/coresight/coresight-trbe.c | 34 +++++++------------- 1 file changed, 12 insertions(+), 22 deletions(-) diff --git a/drivers/hwtracing/coresight/coresight-trbe.c b/drivers/hwtracing/coresight/coresight-trbe.c index 176868496879..ec38cf17b693 100644 --- a/drivers/hwtracing/coresight/coresight-trbe.c +++ b/drivers/hwtracing/coresight/coresight-trbe.c @@ -696,10 +696,8 @@ static void trbe_handle_spurious(struct perf_output_handle *handle) static void trbe_handle_overflow(struct perf_output_handle *handle) { - struct perf_event *event = handle->event; struct trbe_buf *buf = etm_perf_sink_config(handle); unsigned long offset, size; - struct etm_event_data *event_data; offset = get_trbe_limit_pointer() - get_trbe_base_pointer(); size = offset - PERF_IDX2OFF(handle->head, buf); @@ -709,30 +707,22 @@ static void trbe_handle_overflow(struct perf_output_handle *handle) /* * Mark the buffer as truncated, as we have stopped the trace * collection upon the WRAP event, without stopping the source. + * + * We don't re-enable the TRBE here, as the event is + * bound to be disabled due to the TRUNCATED flag. + * This is not ideal, as we could use the available space in + * the ring buffer and continue the tracing. + * + * TODO: Revisit the use of TRUNCATED flag and may be instead use + * PARTIAL, to indicate trace may contain partial packets. + * And TRUNCATED can be used only if we do not have enough space + * in the buffer. This would need additional changes in + * etm_event_stop() to allow the sinks to leave a closed + * aux_handle. */ perf_aux_output_flag(handle, PERF_AUX_FLAG_CORESIGHT_FORMAT_RAW | PERF_AUX_FLAG_TRUNCATED); perf_aux_output_end(handle, size); - event_data = perf_aux_output_begin(handle, event); - if (!event_data) { - /* - * We are unable to restart the trace collection, - * thus leave the TRBE disabled. The etm-perf driver - * is able to detect this with a disconnected handle - * (handle->event = NULL). - */ - trbe_drain_and_disable_local(); - *this_cpu_ptr(buf->cpudata->drvdata->handle) = NULL; - return; - } - buf->trbe_limit = compute_trbe_buffer_limit(handle); - buf->trbe_write = buf->trbe_base + PERF_IDX2OFF(handle->head, buf); - if (buf->trbe_limit == buf->trbe_base) { - trbe_stop_and_truncate_event(handle); - return; - } - *this_cpu_ptr(buf->cpudata->drvdata->handle) = handle; - trbe_enable_hw(buf); } static bool is_perf_trbe(struct perf_output_handle *handle) -- 2.24.1