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=-10.3 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS 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 801F3C4727F for ; Wed, 23 Sep 2020 02:26:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 13ABF2071A for ; Wed, 23 Sep 2020 02:26:02 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="PxAUyObV" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727243AbgIWC0B (ORCPT ); Tue, 22 Sep 2020 22:26:01 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:44687 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726893AbgIWC0A (ORCPT ); Tue, 22 Sep 2020 22:26:00 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1600827959; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=IaOuvH8yFcLP2XPWL4s+SHZG/coSY9ya51DgWC/DIGU=; b=PxAUyObV0vRZ0stkMFTIx5Qs806HzcPafSaQemCdJrRwJLXBqIV/Ongi/j5cjQaGzhxZ1p Vl68E0i9366LwtXpa5Fqq5XnPVFbX/pBC6ynadqNnxycEKv2tXPTBbuldbu5+tFLJalKYP 0AbhZu3hosCYvMEQhQsTLD0tc9aQBq4= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-547-RGscsW6kPv6qxTolwEEfYA-1; Tue, 22 Sep 2020 22:25:55 -0400 X-MC-Unique: RGscsW6kPv6qxTolwEEfYA-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id DA7871006704; Wed, 23 Sep 2020 02:25:53 +0000 (UTC) Received: from dhcp-128-65.nay.redhat.com (ovpn-13-77.pek2.redhat.com [10.72.13.77]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 99C1C5C1D0; Wed, 23 Sep 2020 02:25:50 +0000 (UTC) Date: Wed, 23 Sep 2020 10:25:47 +0800 From: Dave Young To: Konrad Rzeszutek Wilk Cc: Andrew Morton , bhe@redhat.com, Eric Biederman , linux-kernel@vger.kernel.org, kexec@lists.infradead.org, Eric DeVolder , Boris Ostrovsky Subject: Re: [PATCH] Only allow to set crash_kexec_post_notifiers on boot time Message-ID: <20200923022547.GA3642@dhcp-128-65.nay.redhat.com> References: <20200918032546.GA4180@dhcp-128-65.nay.redhat.com> <20200918174743.0994c59f058451948837dcb6@linux-foundation.org> <20200921201811.GB3437@char.us.oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200921201811.GB3437@char.us.oracle.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 09/21/20 at 04:18pm, Konrad Rzeszutek Wilk wrote: > On Fri, Sep 18, 2020 at 05:47:43PM -0700, Andrew Morton wrote: > > On Fri, 18 Sep 2020 11:25:46 +0800 Dave Young wrote: > > > > > crash_kexec_post_notifiers enables running various panic notifier > > > before kdump kernel booting. This increases risks of kdump failure. > > > It is well documented in kernel-parameters.txt. We do not suggest > > > people to enable it together with kdump unless he/she is really sure. > > > This is also not suggested to be enabled by default when users are > > > not aware in distributions. > > > > > > But unfortunately it is enabled by default in systemd, see below > > > discussions in a systemd report, we can not convince systemd to change > > > it: > > > https://github.com/systemd/systemd/issues/16661 > > > > > > Actually we have got reports about kdump kernel hangs in both s390x > > > and powerpcle cases caused by the systemd change, also some x86 cases > > > could also be caused by the same (although that is in Hyper-V code > > > instead of systemd, that need to be addressed separately). > > Perhaps it may be better to fix the issus on s390x and PowerPC as well? > > > > > > > Thus to avoid the auto enablement here just disable the param writable > > > permission in sysfs. > > > > > > > Well. I don't think this is at all a desirable way of resolving a > > disagreement with the systemd developers > > > > At the above github address I'm seeing "ryncsn added a commit to > > ryncsn/systemd that referenced this issue 9 days ago", "pstore: don't > > enable crash_kexec_post_notifiers by default". So didn't that address > > the issue? > > It does in systemd, but there is a strong interest in making this on by default. I understand there could be such interest, but we have to keep in mind that any extra things after a system crash can cause kdump unreliable. I do not object people to use pstore, but I do object to enable the notifiers by default. BTW, crash notifiers are not limited to pstore, there are quite a log of other pieces like led trigger etc. Thanks Dave