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=-16.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, 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 D648DC4338F for ; Fri, 30 Jul 2021 04:15:56 +0000 (UTC) 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 mail.kernel.org (Postfix) with ESMTPS id 9B60060527 for ; Fri, 30 Jul 2021 04:15:56 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 9B60060527 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:Date: Message-ID:From:References:Cc:To:Subject:Reply-To:Content-ID: Content-Description:Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc :Resent-Message-ID:List-Owner; bh=N8ELj2LNflUmKTOVcq9Kfsv+uv6ko2msgQr+QjJZ+B4=; b=J9KunAKS+Ajc93XLp5HFxUC9E8 C+38yyDgs1H0ZQkpbZpj2LaXfoNtqBk+EWmGyuelhL7qXgR8rD6S5hHMbFnIYbQP+gFUjrOaBJsPw xT7weC3wvacAyViUUaxDo0uPAthV7l34lT3LIvIGxdQf6SD+UYdsbrGRncTNHhDh9IIqVfpSW9/Tg tSEOSkdOz6Atmhn7xuOKF3OLRzunMwvAPs7qq13zWJ6WmBQMhUembtiqltN/1ysnBssggEeKUG9WK hnmK90yfl4vY5adgtnhcQtR8HjTw4qP9z058oKkVY8s+HyLberrBzUR3cPV0D2mTRu5G/mm9WuqR+ OVyr0vZA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1m9JuI-0073EN-A0; Fri, 30 Jul 2021 04:13:58 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1m9JuE-0073DE-At for linux-arm-kernel@lists.infradead.org; Fri, 30 Jul 2021 04:13:55 +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 5725931B; Thu, 29 Jul 2021 21:13:46 -0700 (PDT) Received: from [10.163.66.9] (unknown [10.163.66.9]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 3CDD93F73D; Thu, 29 Jul 2021 21:13:42 -0700 (PDT) Subject: Re: [PATCH v2 03/10] coresight: etm-pmu: Ensure the AUX handle is valid To: Suzuki K Poulose , coresight@lists.linaro.org Cc: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, tamas.zsoldos@arm.com, al.grant@arm.com, leo.yan@linaro.org, mike.leach@linaro.org, mathieu.poirier@linaro.org, jinlmao@qti.qualcomm.com References: <20210723124611.3828908-1-suzuki.poulose@arm.com> <20210723124611.3828908-4-suzuki.poulose@arm.com> From: Anshuman Khandual Message-ID: Date: Fri, 30 Jul 2021 09:44:31 +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: <20210723124611.3828908-4-suzuki.poulose@arm.com> Content-Language: en-US X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210729_211354_480372_9219FB58 X-CRM114-Status: GOOD ( 24.91 ) 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: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 7/23/21 6:16 PM, Suzuki K Poulose wrote: > The ETM perf infrastructure closes out a handle during event_stop > or on an error in starting the event. In either case, it is possible > for a "sink" to update/close the handle, under certain circumstances. > (e.g no space in ring buffer.). So, ensure that we handle this > gracefully in the PMU driver by verifying the handle is still valid. > > Cc: Mathieu Poirier > Cc: Mike Leach > Cc: Anshuman Khandual > Cc: Leo Yan > Signed-off-by: Suzuki K Poulose > --- > .../hwtracing/coresight/coresight-etm-perf.c | 27 ++++++++++++++++--- > 1 file changed, 24 insertions(+), 3 deletions(-) > > diff --git a/drivers/hwtracing/coresight/coresight-etm-perf.c b/drivers/hwtracing/coresight/coresight-etm-perf.c > index 6f398377fec9..a6ab603afee4 100644 > --- a/drivers/hwtracing/coresight/coresight-etm-perf.c > +++ b/drivers/hwtracing/coresight/coresight-etm-perf.c > @@ -450,8 +450,15 @@ static void etm_event_start(struct perf_event *event, int flags) > fail_disable_path: > coresight_disable_path(path); > fail_end_stop: > - perf_aux_output_flag(handle, PERF_AUX_FLAG_TRUNCATED); > - perf_aux_output_end(handle, 0); > + /* > + * Check if the handle is still associated with the event, > + * to handle cases where if the sink failed to start the > + * trace and TRUNCATED the handle already. > + */ > + if (READ_ONCE(handle->event)) { > + perf_aux_output_flag(handle, PERF_AUX_FLAG_TRUNCATED); > + perf_aux_output_end(handle, 0); > + } Makes sense as perf_aux_output_[flag|end]() helpers do not validate the 'handle' themselves. > fail: > event->hw.state = PERF_HES_STOPPED; > goto out; > @@ -519,7 +526,21 @@ static void etm_event_stop(struct perf_event *event, int mode) > > size = sink_ops(sink)->update_buffer(sink, handle, > event_data->snk_config); > - perf_aux_output_end(handle, size); > + /* > + * Make sure the handle is still valid as the > + * sink could have closed it from an IRQ. > + * The sink driver must handle the race with > + * update_buffer() and IRQ. Thus either we > + * should get a valid handle and valid size > + * (which may be 0). > + * > + * But we should never get a non-zero size with > + * an invalid handle. > + */ > + if (READ_ONCE(handle->event)) > + perf_aux_output_end(handle, size); > + else > + WARN_ON(size); Right. > } > > /* Disabling the path make its elements available to other sessions */ > Reviewed-by: Anshuman Khandual _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel