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Tue, 22 Sep 2020 10:58:10 +0000 (GMT) Received: from ibm (unknown [9.145.153.226]) by d06av21.portsmouth.uk.ibm.com (Postfix) with ESMTP id 57C6652054; Tue, 22 Sep 2020 10:58:10 +0000 (GMT) Date: Tue, 22 Sep 2020 12:58:09 +0200 From: Philipp Rudo To: Konrad Rzeszutek Wilk Cc: Andrew Morton , bhe@redhat.com, kexec@lists.infradead.org, linux-kernel@vger.kernel.org, Eric Biederman , Boris Ostrovsky , Eric DeVolder , Dave Young Subject: Re: [PATCH] Only allow to set crash_kexec_post_notifiers on boot time Message-ID: <20200922125809.66690d54@ibm> In-Reply-To: <20200921201811.GB3437@char.us.oracle.com> References: <20200918032546.GA4180@dhcp-128-65.nay.redhat.com> <20200918174743.0994c59f058451948837dcb6@linux-foundation.org> <20200921201811.GB3437@char.us.oracle.com> Organization: IBM X-Mailer: Claws Mail 3.17.6 (GTK+ 2.24.32; x86_64-redhat-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.235,18.0.687 definitions=2020-09-22_06:2020-09-21,2020-09-22 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 phishscore=0 priorityscore=1501 bulkscore=0 mlxscore=0 adultscore=0 malwarescore=0 mlxlogscore=999 spamscore=0 clxscore=1011 lowpriorityscore=0 suspectscore=0 impostorscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2006250000 definitions=main-2009220083 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Konrad, On Mon, 21 Sep 2020 16:18:12 -0400 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? There's little s390 can fix. We use the panic_notifier_list to start other dumpers in case kdump isn't configured or failed. This behavior was introduced in 2006 long before crash_kexec_post_notifiers were introduced. So I suggest that crash_kexec_post_notifiers are fixed instead. > > > > > > 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. AFAIK pstore requires UEFI to work. So what's the point to enable it on non-UEFI systems? Thanks Philipp From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]) by merlin.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1kKg09-0000KT-1O for kexec@lists.infradead.org; Tue, 22 Sep 2020 10:58:27 +0000 Date: Tue, 22 Sep 2020 12:58:09 +0200 From: Philipp Rudo Subject: Re: [PATCH] Only allow to set crash_kexec_post_notifiers on boot time Message-ID: <20200922125809.66690d54@ibm> In-Reply-To: <20200921201811.GB3437@char.us.oracle.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 List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "kexec" Errors-To: kexec-bounces+dwmw2=infradead.org@lists.infradead.org To: Konrad Rzeszutek Wilk Cc: bhe@redhat.com, kexec@lists.infradead.org, linux-kernel@vger.kernel.org, Eric Biederman , Boris Ostrovsky , Eric DeVolder , Dave Young , Andrew Morton Hi Konrad, On Mon, 21 Sep 2020 16:18:12 -0400 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? There's little s390 can fix. We use the panic_notifier_list to start other dumpers in case kdump isn't configured or failed. This behavior was introduced in 2006 long before crash_kexec_post_notifiers were introduced. So I suggest that crash_kexec_post_notifiers are fixed instead. > > > > > > 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. AFAIK pstore requires UEFI to work. So what's the point to enable it on non-UEFI systems? Thanks Philipp _______________________________________________ kexec mailing list kexec@lists.infradead.org http://lists.infradead.org/mailman/listinfo/kexec