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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5741AC00144 for ; Fri, 29 Jul 2022 09:05:56 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235586AbiG2JFy (ORCPT ); Fri, 29 Jul 2022 05:05:54 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41600 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235485AbiG2JFm (ORCPT ); Fri, 29 Jul 2022 05:05:42 -0400 Received: from sin.source.kernel.org (sin.source.kernel.org [145.40.73.55]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 4D2D177A65; Fri, 29 Jul 2022 02:05:41 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by sin.source.kernel.org (Postfix) with ESMTPS id 6A75ECE2586; Fri, 29 Jul 2022 09:05:39 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id F2401C433C1; Fri, 29 Jul 2022 09:05:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1659085537; bh=wvE5EHGmPigV4oD45oTwiHHUQ4e3yEtd8+Rek83/iZI=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=u4XFhk2DKQ9ZhFdCgE/O1FOABLAVZrwk5XV7UmcIVw0wNVMKeJ8oCvvhbPIuruugH lVJ16TpQyhX33sT2ppx+Igx96tQu+Ozi3VhO8Fp70k/RFxgMPRPKZr5MSGiWsvJ9GD Wn1kY+HYPAecHr7gurrqG2aWeXQUfEWMgIiVr7Ps= Date: Fri, 29 Jul 2022 11:05:34 +0200 From: Greg KH To: Yicong Yang Cc: yangyicong@hisilicon.com, alexander.shishkin@linux.intel.com, leo.yan@linaro.org, james.clark@arm.com, will@kernel.org, robin.murphy@arm.com, acme@kernel.org, peterz@infradead.org, corbet@lwn.net, mathieu.poirier@linaro.org, mark.rutland@arm.com, jonathan.cameron@huawei.com, john.garry@huawei.com, helgaas@kernel.org, lorenzo.pieralisi@arm.com, suzuki.poulose@arm.com, joro@8bytes.org, shameerali.kolothum.thodi@huawei.com, mingo@redhat.com, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-pci@vger.kernel.org, linux-perf-users@vger.kernel.org, iommu@lists.linux-foundation.org, iommu@lists.linux.dev, linux-doc@vger.kernel.org, prime.zeng@huawei.com, liuqi115@huawei.com, zhangshaokun@hisilicon.com, linuxarm@huawei.com, bagasdotme@gmail.com Subject: Re: [PATCH v11 2/8] hwtracing: hisi_ptt: Add trace function support for HiSilicon PCIe Tune and Trace device Message-ID: References: <20220721130116.43366-1-yangyicong@huawei.com> <20220721130116.43366-3-yangyicong@huawei.com> <33f372f6-36bf-f84e-bca0-86347fa4d579@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <33f372f6-36bf-f84e-bca0-86347fa4d579@huawei.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jul 29, 2022 at 03:29:14PM +0800, Yicong Yang wrote: > >> + /* > >> + * Handle the interrupt on the same cpu which starts the trace to avoid > >> + * context mismatch. Otherwise we'll trigger the WARN from the perf > >> + * core in event_function_local(). > >> + */ > >> + WARN_ON(irq_set_affinity(pci_irq_vector(hisi_ptt->pdev, HISI_PTT_TRACE_DMA_IRQ), > >> + cpumask_of(cpu))); > > > > If this hits, you just crashed the machine :( > > > > We'll likely to have a calltrace here without crash the machine and reboot in > most time, unless user has set panic_on_warn. Again, please do not use WARN_ON for this, please read: https://elixir.bootlin.com/linux/v5.19-rc8/source/include/asm-generic/bug.h#L74 If you want a traceback (what would you do with that?), then call the function to give you that. Don't crash people's boxes. > > Please properly recover from errors if you hit them, like this. Don't > > just give up and throw a message to userspace and watch the machine > > reboot with all data lost. > > > > Same for the other WARN_ON() instances here. Handle the error and > > report it properly up the call chain. > > > > The driver use WARN_ON() in two places, once in pmu::start() and another in cpu teardown's > callback, both when the irq_set_affinity() failed. This is common to behave so when driver > fails to set irq affinity in pmu::start() and cpu_teardown(): Don't repeat broken patterns please. > yangyicong@ubuntu:~/mainline_linux/linux/drivers$ grep -rn WARN_ON ./ | grep irq_set_affinity > ./perf/arm_smmuv3_pmu.c:649: WARN_ON(irq_set_affinity(smmu_pmu->irq, cpumask_of(target))); > ./perf/arm_smmuv3_pmu.c:895: WARN_ON(irq_set_affinity(smmu_pmu->irq, cpumask_of(smmu_pmu->on_cpu))); > ./perf/arm-ccn.c:1214: WARN_ON(irq_set_affinity(ccn->irq, cpumask_of(dt->cpu))); > ./perf/qcom_l2_pmu.c:796: WARN_ON(irq_set_affinity(cluster->irq, cpumask_of(cpu))); > ./perf/qcom_l2_pmu.c:834: WARN_ON(irq_set_affinity(cluster->irq, cpumask_of(target))); > ./perf/arm_dmc620_pmu.c:624: WARN_ON(irq_set_affinity(irq->irq_num, cpumask_of(target))); > ./perf/fsl_imx8_ddr_perf.c:674: WARN_ON(irq_set_affinity(pmu->irq, cpumask_of(pmu->cpu))); > ./perf/xgene_pmu.c:1793: WARN_ON(irq_set_affinity(xgene_pmu->irq, &xgene_pmu->cpu)); > ./perf/xgene_pmu.c:1826: WARN_ON(irq_set_affinity(xgene_pmu->irq, &xgene_pmu->cpu)); > ./perf/hisilicon/hisi_pcie_pmu.c:658: WARN_ON(irq_set_affinity(pcie_pmu->irq, cpumask_of(cpu))); > ./perf/hisilicon/hisi_pcie_pmu.c:684: WARN_ON(irq_set_affinity(pcie_pmu->irq, cpumask_of(target))); > ./perf/hisilicon/hisi_uncore_pmu.c:495: WARN_ON(irq_set_affinity(hisi_pmu->irq, cpumask_of(cpu))); > ./perf/hisilicon/hisi_uncore_pmu.c:528: WARN_ON(irq_set_affinity(hisi_pmu->irq, cpumask_of(target))); Great, you can fix all of these up as well any time :) thanks, greg k-h