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=-5.9 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A, SPF_HELO_NONE,SPF_PASS,TRACKER_ID,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=no 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 365B2C433DF for ; Fri, 31 Jul 2020 16:08:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0C2CD208E4 for ; Fri, 31 Jul 2020 16:08:22 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="kqqSiqku" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729475AbgGaQIU (ORCPT ); Fri, 31 Jul 2020 12:08:20 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37636 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728693AbgGaQIU (ORCPT ); Fri, 31 Jul 2020 12:08:20 -0400 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0A1D7C061574 for ; Fri, 31 Jul 2020 09:08:20 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=Content-Transfer-Encoding:Content-Type: In-Reply-To:MIME-Version:Date:Message-ID:From:References:Cc:To:Subject:Sender :Reply-To:Content-ID:Content-Description; bh=E8OutGXDvinZ9nc9PDwwcZ7dYyARjf7spI4x4vTTasM=; b=kqqSiqkuAu9N4FwMiyAgZ0tMmM MUTqJHCeUkgh3SYpV5meNlSkEty4qznhTVEIRwhgBrptGdWzC6FYQN8foxhu2vSFam5vUYEluQhvC IDaNLEGo9vlGaehDKHXDVikGJBOw8NAWtasBG4skcLfCf9bhHx2vJtoFP0LURtY7dp9EdGPXJs8sc wLDlV1O4dRq/4bFYx12EbOZpoWsKyp0T4maeM7stV7EW7lTFnRgAUpyJ0UuMusTGqAT20HmOIALTO WIHjBFDSukk7YPcnw1KH5ZN+YFsGudyy/ECjTOG0WItWGURejmU7V12BoP2ySnGZM8/EbvUbo04QC OTqGI0cA==; Received: from [2601:1c0:6280:3f0:897c:6038:c71d:ecac] by casper.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1k1XZv-0004Ss-Gu; Fri, 31 Jul 2020 16:08:16 +0000 Subject: Re: upstream boot error: BUG: soft lockup in __do_softirq To: Dmitry Vyukov , syzbot Cc: Borislav Petkov , "H. Peter Anvin" , LKML , Andy Lutomirski , Ingo Molnar , syzkaller-bugs , Thomas Gleixner , the arch/x86 maintainers , "Paul E. McKenney" References: <00000000000060adcb05abb71eb6@google.com> From: Randy Dunlap Message-ID: <7e93543a-ff0c-2433-7bed-4053da59d5c2@infradead.org> Date: Fri, 31 Jul 2020 09:08:11 -0700 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: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 7/30/20 11:50 PM, Dmitry Vyukov wrote: > On Fri, Jul 31, 2020 at 8:44 AM syzbot > wrote: >> >> Hello, >> >> syzbot found the following issue on: >> >> HEAD commit: 92ed3019 Linux 5.8-rc7 >> git tree: upstream >> console output: https://syzkaller.appspot.com/x/log.txt?x=10e84cdf100000 >> kernel config: https://syzkaller.appspot.com/x/.config?x=b45e47f6d958ae82 >> dashboard link: https://syzkaller.appspot.com/bug?extid=8472ea265fe32cc3bf78 >> compiler: gcc (GCC) 10.1.0-syz 20200507 >> >> IMPORTANT: if you fix the issue, please add the following tag to the commit: >> Reported-by: syzbot+8472ea265fe32cc3bf78@syzkaller.appspotmail.com > > This is a qemu-kvm instance killing the host kernel somehow, the host > kernel itself running qemu's is full of rcu stalls. I think this is > not a bug in the tested kernel. > We change rcu stall timeout to 120 seconds from the default 21s, but > this happens only after boot using sysctls. I did not find any way to > change the rcu timeout via cmdline/config (would be useful). (adding Paul) Documentation/RCU/stallwarn.rst says there is a Kconfig: CONFIG_RCU_CPU_STALL_TIMEOUT This kernel configuration parameter defines the period of time that RCU will wait from the beginning of a grace period until it issues an RCU CPU stall warning. This time period is normally 21 seconds. and Documentation/admin-guide/kernel-parameters.txt has 2 RCU stall timeouts, one for CPU and one for tasks: rcupdate.rcu_cpu_stall_timeout= [KNL] Set timeout for RCU CPU stall warning messages. rcupdate.rcu_task_stall_timeout= [KNL] Set timeout in jiffies for RCU task stall warning messages. Disable with a value less than or equal to zero. -- ~Randy