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=-15.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, 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 0B745C433F5 for ; Wed, 22 Sep 2021 09:57:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E75FB61156 for ; Wed, 22 Sep 2021 09:57:20 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234575AbhIVJ6t (ORCPT ); Wed, 22 Sep 2021 05:58:49 -0400 Received: from foss.arm.com ([217.140.110.172]:45970 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234413AbhIVJ6r (ORCPT ); Wed, 22 Sep 2021 05:58:47 -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 7246A11B3; Wed, 22 Sep 2021 02:57:17 -0700 (PDT) Received: from [10.163.73.113] (unknown [10.163.73.113]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id D3F0D3F719; Wed, 22 Sep 2021 02:57:13 -0700 (PDT) Subject: Re: [PATCH v2 14/17] coresight: trbe: Make sure we have enough space To: Suzuki K Poulose , linux-arm-kernel@lists.infradead.org Cc: linux-kernel@vger.kernel.org, maz@kernel.org, catalin.marinas@arm.com, mark.rutland@arm.com, james.morse@arm.com, leo.yan@linaro.org, mike.leach@linaro.org, mathieu.poirier@linaro.org, will@kernel.org, lcherian@marvell.com, coresight@lists.linaro.org References: <20210921134121.2423546-1-suzuki.poulose@arm.com> <20210921134121.2423546-15-suzuki.poulose@arm.com> From: Anshuman Khandual Message-ID: <60e75e7b-4a04-03d4-c861-88dd5fadef99@arm.com> Date: Wed, 22 Sep 2021 15:28:21 +0530 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: <20210921134121.2423546-15-suzuki.poulose@arm.com> 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 9/21/21 7:11 PM, Suzuki K Poulose wrote: > The TRBE driver makes sure that there is enough space for a meaningful > run, otherwise pads the given space and restarts the offset calculation > once. But there is no guarantee that we may find space or hit "no space". So what happens currently when it neither finds the required minimum buffer space for a meaningful run nor does it hit the "no space" scenario ? > Make sure that we repeat the step until, either : > - We have the minimum space > OR > - There is NO space at all. > > Cc: Anshuman Khandual > Cc: Mathieu Poirier > Cc: Mike Leach > Cc: Leo Yan > Signed-off-by: Suzuki K Poulose > --- > drivers/hwtracing/coresight/coresight-trbe.c | 6 +++++- > 1 file changed, 5 insertions(+), 1 deletion(-) > > diff --git a/drivers/hwtracing/coresight/coresight-trbe.c b/drivers/hwtracing/coresight/coresight-trbe.c > index 3373f4e2183b..02f9e00e2091 100644 > --- a/drivers/hwtracing/coresight/coresight-trbe.c > +++ b/drivers/hwtracing/coresight/coresight-trbe.c > @@ -451,10 +451,14 @@ static unsigned long trbe_normal_offset(struct perf_output_handle *handle) > * If the head is too close to the limit and we don't > * have space for a meaningful run, we rather pad it > * and start fresh. > + * > + * We might have to do this more than once to make sure > + * we have enough required space. OR no space at all, as explained in the commit message. Hence this comment needs an update. > */ > - if (limit && ((limit - head) < trbe_min_trace_buf_size(handle))) { > + while (limit && ((limit - head) < trbe_min_trace_buf_size(handle))) { > trbe_pad_buf(handle, limit - head); > limit = __trbe_normal_offset(handle); > + head = PERF_IDX2OFF(handle->head, buf); Should the loop be bound with a retry limit as well ? > } > return limit; > } >