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=-5.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,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 4ED41C3F2D2 for ; Mon, 2 Mar 2020 08:09:11 +0000 (UTC) Received: from lists.ozlabs.org (lists.ozlabs.org [203.11.71.2]) (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 C16282468E for ; Mon, 2 Mar 2020 08:09:10 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org C16282468E Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.ibm.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Received: from lists.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3]) by lists.ozlabs.org (Postfix) with ESMTP id 48WCTc2sLJzDqf4 for ; Mon, 2 Mar 2020 19:09:08 +1100 (AEDT) Authentication-Results: lists.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=linux.ibm.com (client-ip=148.163.156.1; helo=mx0a-001b2d01.pphosted.com; envelope-from=hbathini@linux.ibm.com; receiver=) Authentication-Results: lists.ozlabs.org; dmarc=none (p=none dis=none) header.from=linux.ibm.com Received: from mx0a-001b2d01.pphosted.com (mx0a-001b2d01.pphosted.com [148.163.156.1]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 48WCRc0fXLzDqdD for ; Mon, 2 Mar 2020 19:07:20 +1100 (AEDT) Received: from pps.filterd (m0098399.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.42/8.16.0.42) with SMTP id 02284LHo100082 for ; Mon, 2 Mar 2020 03:07:17 -0500 Received: from e06smtp05.uk.ibm.com (e06smtp05.uk.ibm.com [195.75.94.101]) by mx0a-001b2d01.pphosted.com with ESMTP id 2yfn0677vr-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Mon, 02 Mar 2020 03:07:17 -0500 Received: from localhost by e06smtp05.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! 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Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Mon, 2 Mar 2020 08:07:13 -0000 Received: from d06av25.portsmouth.uk.ibm.com (d06av25.portsmouth.uk.ibm.com [9.149.105.61]) by b06cxnps3075.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 02287CQF58196036 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Mon, 2 Mar 2020 08:07:12 GMT Received: from d06av25.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 04B5B11C054; Mon, 2 Mar 2020 08:07:12 +0000 (GMT) Received: from d06av25.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id D842211C050; Mon, 2 Mar 2020 08:07:09 +0000 (GMT) Received: from [9.85.85.34] (unknown [9.85.85.34]) by d06av25.portsmouth.uk.ibm.com (Postfix) with ESMTP; Mon, 2 Mar 2020 08:07:09 +0000 (GMT) Subject: Re: [PATCH 2/2] powerpc/pseries: update device tree before ejecting hotplug uevents To: Pingfan Liu , linuxppc-dev@lists.ozlabs.org References: <1581389982-5701-1-git-send-email-kernelfans@gmail.com> <1581389982-5701-2-git-send-email-kernelfans@gmail.com> From: Hari Bathini Date: Mon, 2 Mar 2020 13:37:07 +0530 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.9.0 MIME-Version: 1.0 In-Reply-To: <1581389982-5701-2-git-send-email-kernelfans@gmail.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 x-cbid: 20030208-0020-0000-0000-000003AF6A25 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 20030208-0021-0000-0000-0000220793E5 Message-Id: X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.138, 18.0.572 definitions=2020-03-02_02:2020-02-28, 2020-03-02 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 bulkscore=0 lowpriorityscore=0 suspectscore=0 mlxscore=0 mlxlogscore=999 impostorscore=0 adultscore=0 spamscore=0 priorityscore=1501 phishscore=0 malwarescore=0 clxscore=1011 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2001150001 definitions=main-2003020062 X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Paul Mackerras , kexec@lists.infradead.org Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On 11/02/20 8:29 AM, Pingfan Liu wrote: > A bug is observed on pseries by taking the following steps on rhel: > -1. drmgr -c mem -r -q 5 > -2. echo c > /proc/sysrq-trigger > > And then, the failure looks like: > kdump: saving to /sysroot//var/crash/127.0.0.1-2020-01-16-02:06:14/ > kdump: saving vmcore-dmesg.txt > kdump: saving vmcore-dmesg.txt complete > kdump: saving vmcore > Checking for memory holes : [ 0.0 %] / Checking for memory holes : [100.0 %] | Excluding unnecessary pages : [100.0 %] \ Copying data : [ 0.3 %] - eta: 38s[ 44.337636] hash-mmu: mm: Hashing failure ! EA=0x7fffba400000 access=0x8000000000000004 current=makedumpfile > [ 44.337663] hash-mmu: trap=0x300 vsid=0x13a109c ssize=1 base psize=2 psize 2 pte=0xc000000050000504 > [ 44.337677] hash-mmu: mm: Hashing failure ! EA=0x7fffba400000 access=0x8000000000000004 current=makedumpfile > [ 44.337692] hash-mmu: trap=0x300 vsid=0x13a109c ssize=1 base psize=2 psize 2 pte=0xc000000050000504 > [ 44.337708] makedumpfile[469]: unhandled signal 7 at 00007fffba400000 nip 00007fffbbc4d7fc lr 000000011356ca3c code 2 > [ 44.338548] Core dump to |/bin/false pipe failed > /lib/kdump-lib-initramfs.sh: line 98: 469 Bus error $CORE_COLLECTOR /proc/vmcore $_mp/$KDUMP_PATH/$HOST_IP-$DATEDIR/vmcore-incomplete > kdump: saving vmcore failed > > * Root cause * > After analyzing, it turns out that in the current implementation, > when hot-removing lmb, the KOBJ_REMOVE event ejects before the dt updating as > the code __remove_memory() comes before drmem_update_dt(). > > From a viewpoint of listener and publisher, the publisher notifies the > listener before data is ready. This introduces a problem where udev > launches kexec-tools (due to KOBJ_REMOVE) and loads a stale dt before > updating. And in capture kernel, makedumpfile will access the memory based > on the stale dt info, and hit a SIGBUS error due to an un-existed lmb. > > * Fix * > In order to fix this issue, update dt before __remove_memory(), and > accordingly the same rule in hot-add path. > > This will introduce extra dt updating payload for each involved lmb when hotplug. > But it should be fine since drmem_update_dt() is memory based operation and > hotplug is not a hot path. > > Signed-off-by: Pingfan Liu > Cc: Michael Ellerman > Cc: Benjamin Herrenschmidt > Cc: Paul Mackerras > Cc: Hari Bathini > To: linuxppc-dev@lists.ozlabs.org > Cc: kexec@lists.infradead.org KDump fails to capture vmcore as we end up looking at a stale elfcore hdr with udev event happening before DT update. Resolved with these patches. For the series: Tested-by: Hari Bathini