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[23.128.96.18]) by mx.google.com with ESMTP id nw21si7558282ejb.404.2020.10.26.08.09.31; Mon, 26 Oct 2020 08:09:54 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18; Authentication-Results: mx.google.com; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=canonical.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1783162AbgJZPG6 (ORCPT + 99 others); Mon, 26 Oct 2020 11:06:58 -0400 Received: from youngberry.canonical.com ([91.189.89.112]:56590 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1747645AbgJZPG5 (ORCPT ); Mon, 26 Oct 2020 11:06:57 -0400 Received: from mail-ej1-f71.google.com ([209.85.218.71]) by youngberry.canonical.com with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.86_2) (envelope-from ) id 1kX45H-0004Ps-8I for linux-kernel@vger.kernel.org; Mon, 26 Oct 2020 15:06:55 +0000 Received: by mail-ej1-f71.google.com with SMTP id b19so5156447eju.7 for ; Mon, 26 Oct 2020 08:06:55 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=EnLWDCtLm8RMcdow/BSYVBH9rX7uMoRshyF3616LTAE=; b=gLYwcqgaFAUD/8U8GAd2v75QVcddcIyLmqHSW/ksUYFRW8V7s3uYkupVsB1AOT++AR fTKYBBtmbQ5W5uWHQc45vwaNEQNgU+13kt4Q5MIVWx7LXi+zSQ+UGOql+JG3x5lytmQ2 Ryq62mG9Qf8VbRtcMkFESKJLwfHqoKpICCBfVMij4QPIKvIIueXmUXBwnKcERZlGwwXT Ex7DvL2SpbJwKkQzr8BXA3NtERd5oT3BTbcofcdJQs1m6uEswreyrRX1H7OIokA29PgN axJzaQryam20sQ1LBJ3/Io9DB16g2g18X4WY5iUKXMkUN0IMSTCVjtaov3TkeBQZ9U0S iCcg== X-Gm-Message-State: AOAM530WP+Y5ru+mFNUS6ISYID85Ra6NOiO4V34K1kXGoiwYDbjT2Wm1 auk9ZC0kFgSLiZ4sZa1zwNTY7IFCw0h55F1BSZh0qx7SgAzeh8RT0Vbx99mxfJLnJTQJbzSa8K8 EtPi16D1CW8bn0gM1MHGDeeA5IQqsEdANEqT7NgmmH6f+jcmAUMqCWDFA1A== X-Received: by 2002:a17:906:c7d9:: with SMTP id dc25mr16060255ejb.482.1603724814867; Mon, 26 Oct 2020 08:06:54 -0700 (PDT) X-Received: by 2002:a17:906:c7d9:: with SMTP id dc25mr16060111ejb.482.1603724813209; Mon, 26 Oct 2020 08:06:53 -0700 (PDT) MIME-Version: 1.0 References: <1603346163-21645-1-git-send-email-kernelfans@gmail.com> <871rhq7j1h.fsf@nanos.tec.linutronix.de> In-Reply-To: From: Guilherme Piccoli Date: Mon, 26 Oct 2020 12:06:17 -0300 Message-ID: Subject: Re: [PATCH 0/3] warn and suppress irqflood To: Pingfan Liu Cc: Thomas Gleixner , LKML , Peter Zijlstra , Jisheng Zhang , Andrew Morton , Petr Mladek , Marc Zyngier , Linus Walleij , afzal mohammed , Lina Iyer , "Gustavo A. R. Silva" , Maulik Shah , Al Viro , Jonathan Corbet , Pawan Gupta , Mike Kravetz , Oliver Neukum , linux-doc@vger.kernel.org, Kexec Mailing List Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Oct 25, 2020 at 8:12 AM Pingfan Liu wrote: > > On Thu, Oct 22, 2020 at 4:37 PM Thomas Gleixner wrote: > > > > On Thu, Oct 22 2020 at 13:56, Pingfan Liu wrote: > > > I hit a irqflood bug on powerpc platform, and two years ago, on a x86 platform. > > > When the bug happens, the kernel is totally occupies by irq. Currently, there > > > may be nothing or just soft lockup warning showed in console. It is better > > > to warn users with irq flood info. > > > > > > In the kdump case, the kernel can move on by suppressing the irq flood. > > > > You're curing the symptom not the cause and the cure is just magic and > > can't work reliably. > Yeah, it is magic. But at least, it is better to printk something and > alarm users about what happens. With current code, it may show nothing > when system hangs. Thanks Pingfan and Thomas for the points - I'd like to have a mechanism in the kernel to warn users when an IRQ flood is potentially happening. Some time ago (2 years) we faced a similar issue in x86-64, a hard to debug problem in kdump, that eventually was narrowed to a buggy NIC FW flooding IRQs in kdump kernel, and no messages showed (although kernel changed a lot since that time, today we might have better IRQ handling/warning). We tried an early-boot fix, by disabling MSIs (as per PCI spec) early in x86 boot, but it wasn't accepted - Bjorn asked pertinent questions that I couldn't respond (I lost the reproducer) [0]. Cheers, Guilherme [0] lore.kernel.org/linux-pci/20181018183721.27467-1-gpiccoli@canonical.com