From: Peter Zijlstra <peterz@infradead.org>
To: "河合英宏 / KAWAI，HIDEHIRO" <hidehiro.kawai.ez@hitachi.com>
Cc: "x86@kernel.org" <x86@kernel.org>,
"Jonathan Corbet" <corbet@lwn.net>,
"linux-doc@vger.kernel.org" <linux-doc@vger.kernel.org>,
"kexec@lists.infradead.org" <kexec@lists.infradead.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"Michal Hocko" <mhocko@kernel.org>,
"Ingo Molnar" <mingo@redhat.com>,
"Thomas Gleixner" <tglx@linutronix.de>,
"Eric W. Biederman" <ebiederm@xmission.com>,
"H. Peter Anvin" <hpa@zytor.com>,
"平松雅巳 / HIRAMATU，MASAMI" <masami.hiramatsu.pt@hitachi.com>,
"Andrew Morton" <akpm@linux-foundation.org>,
"Ingo Molnar" <mingo@kernel.org>,
"Vivek Goyal" <vgoyal@redhat.com>
Subject: Re: [V4 PATCH 4/4] x86/apic: Introduce noextnmi boot option
Date: Thu, 1 Oct 2015 08:27:33 +0200 [thread overview]
Message-ID: <20151001062733.GL2881@worktop.programming.kicks-ass.net> (raw)
In-Reply-To: <04EAB7311EE43145B2D3536183D1A8445499CD11@GSjpTKYDCembx31.service.hitachi.net>
On Thu, Oct 01, 2015 at 02:33:18AM +0000, 河合英宏 / KAWAI，HIDEHIRO wrote:
> > On Fri, Sep 25, 2015 at 08:28:11PM +0900, Hidehiro Kawai wrote:
> > > This patch introduces new boot option "noextnmi" which disables
> > > external NMI. This option is useful for the dump capture kernel
> > > so that an HA application or administrator wouldn't mistakenly
> > > shoot down the kernel by NMI.
> >
> > So that they can get really stuck when the crash kernel crashes, right?
> > ;-)
>
> No, it is different from my intention.
>
> `mistakenly' in the above means; they issue NMI due to a misconception
> that the monitored host is stuck in the 1st kernel while it is actually
> taking a crash dump in the 2nd kernel. To avoid this kind of accident,
> there is a tool such as fence_kdump which notifies "I'm taking a crash
> dump, so don't send NMI" to the HA clustering software. However, there
> is a time window between kernel panic and the notification.
>
> "noextnmi" allows users to avoid this kind of accident all the time of
> 2nd kernel.
Yes yes, I understand. But if the crash kernel also gets stuck they have
no means of recovery, right? (other than power cycling the hardware)
Just playing devils advocate here, I don't actually object to the patch.
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WARNING: multiple messages have this Message-ID (diff)
From: Peter Zijlstra <peterz@infradead.org>
To: "河合英宏 / KAWAI，HIDEHIRO" <hidehiro.kawai.ez@hitachi.com>
Cc: "Jonathan Corbet" <corbet@lwn.net>,
"Ingo Molnar" <mingo@kernel.org>,
"Eric W. Biederman" <ebiederm@xmission.com>,
"H. Peter Anvin" <hpa@zytor.com>,
"Andrew Morton" <akpm@linux-foundation.org>,
"Thomas Gleixner" <tglx@linutronix.de>,
"Vivek Goyal" <vgoyal@redhat.com>,
"linux-doc@vger.kernel.org" <linux-doc@vger.kernel.org>,
"x86@kernel.org" <x86@kernel.org>,
"kexec@lists.infradead.org" <kexec@lists.infradead.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"Michal Hocko" <mhocko@kernel.org>,
"Ingo Molnar" <mingo@redhat.com>,
"平松雅巳 / HIRAMATU，MASAMI" <masami.hiramatsu.pt@hitachi.com>
Subject: Re: [V4 PATCH 4/4] x86/apic: Introduce noextnmi boot option
Date: Thu, 1 Oct 2015 08:27:33 +0200 [thread overview]
Message-ID: <20151001062733.GL2881@worktop.programming.kicks-ass.net> (raw)
In-Reply-To: <04EAB7311EE43145B2D3536183D1A8445499CD11@GSjpTKYDCembx31.service.hitachi.net>
On Thu, Oct 01, 2015 at 02:33:18AM +0000, 河合英宏 / KAWAI，HIDEHIRO wrote:
> > On Fri, Sep 25, 2015 at 08:28:11PM +0900, Hidehiro Kawai wrote:
> > > This patch introduces new boot option "noextnmi" which disables
> > > external NMI. This option is useful for the dump capture kernel
> > > so that an HA application or administrator wouldn't mistakenly
> > > shoot down the kernel by NMI.
> >
> > So that they can get really stuck when the crash kernel crashes, right?
> > ;-)
>
> No, it is different from my intention.
>
> `mistakenly' in the above means; they issue NMI due to a misconception
> that the monitored host is stuck in the 1st kernel while it is actually
> taking a crash dump in the 2nd kernel. To avoid this kind of accident,
> there is a tool such as fence_kdump which notifies "I'm taking a crash
> dump, so don't send NMI" to the HA clustering software. However, there
> is a time window between kernel panic and the notification.
>
> "noextnmi" allows users to avoid this kind of accident all the time of
> 2nd kernel.
Yes yes, I understand. But if the crash kernel also gets stuck they have
no means of recovery, right? (other than power cycling the hardware)
Just playing devils advocate here, I don't actually object to the patch.
next prev parent reply other threads:[~2015-10-01 6:27 UTC|newest]
Thread overview: 78+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-09-25 11:28 [V4 PATCH 0/4] Fix race issues among panic, NMI and crash_kexec Hidehiro Kawai
2015-09-25 11:28 ` Hidehiro Kawai
2015-09-25 11:28 ` [V4 PATCH 1/4] panic/x86: Fix re-entrance problem due to panic on NMI Hidehiro Kawai
2015-09-25 11:28 ` Hidehiro Kawai
2015-09-25 12:13 ` 河合英宏 / KAWAI，HIDEHIRO
2015-09-25 12:13 ` 河合英宏 / KAWAI，HIDEHIRO
2015-09-30 11:26 ` Peter Zijlstra
2015-09-30 11:26 ` Peter Zijlstra
2015-10-01 1:02 ` 河合英宏 / KAWAI，HIDEHIRO
2015-10-01 1:02 ` 河合英宏 / KAWAI，HIDEHIRO
2015-09-25 11:28 ` [V4 PATCH 2/4] panic/x86: Allow cpus to save registers even if they are looping in NMI context Hidehiro Kawai
2015-09-25 11:28 ` Hidehiro Kawai
2015-09-30 11:50 ` Peter Zijlstra
2015-09-30 11:50 ` Peter Zijlstra
2015-10-01 1:43 ` 河合英宏 / KAWAI，HIDEHIRO
2015-10-01 1:43 ` 河合英宏 / KAWAI，HIDEHIRO
2015-09-25 11:28 ` [V4 PATCH 3/4] kexec: Fix race between panic() and crash_kexec() called directly Hidehiro Kawai
2015-09-25 11:28 ` Hidehiro Kawai
2015-09-28 3:53 ` kbuild test robot
2015-09-28 3:53 ` kbuild test robot
2015-09-28 7:08 ` 河合英宏 / KAWAI，HIDEHIRO
2015-09-28 7:08 ` 河合英宏 / KAWAI，HIDEHIRO
2015-09-30 11:53 ` Peter Zijlstra
2015-09-30 11:53 ` Peter Zijlstra
2015-10-01 2:04 ` 河合英宏 / KAWAI，HIDEHIRO
2015-10-01 2:04 ` 河合英宏 / KAWAI，HIDEHIRO
2015-09-28 4:02 ` kbuild test robot
2015-09-28 4:02 ` kbuild test robot
2015-09-28 4:46 ` 河合英宏 / KAWAI，HIDEHIRO
2015-09-28 4:46 ` 河合英宏 / KAWAI，HIDEHIRO
2015-09-25 11:28 ` [V4 PATCH 4/4] x86/apic: Introduce noextnmi boot option Hidehiro Kawai
2015-09-25 11:28 ` Hidehiro Kawai
2015-09-30 11:55 ` Peter Zijlstra
2015-09-30 11:55 ` Peter Zijlstra
2015-10-01 2:33 ` 河合英宏 / KAWAI，HIDEHIRO
2015-10-01 2:33 ` 河合英宏 / KAWAI，HIDEHIRO
2015-10-01 6:27 ` Peter Zijlstra [this message]
2015-10-01 6:27 ` Peter Zijlstra
2015-10-01 7:01 ` 河合英宏 / KAWAI，HIDEHIRO
2015-10-01 7:01 ` 河合英宏 / KAWAI，HIDEHIRO
2015-10-01 8:43 ` Borislav Petkov
2015-10-01 8:43 ` Borislav Petkov
2015-10-01 10:24 ` 河合英宏 / KAWAI，HIDEHIRO
2015-10-01 10:24 ` 河合英宏 / KAWAI，HIDEHIRO
2015-10-01 11:01 ` Borislav Petkov
2015-10-01 11:01 ` Borislav Petkov
2015-10-02 0:58 ` 河合英宏 / KAWAI，HIDEHIRO
2015-10-02 0:58 ` 河合英宏 / KAWAI，HIDEHIRO
2015-10-02 7:47 ` Borislav Petkov
2015-10-02 7:47 ` Borislav Petkov
2015-10-05 2:03 ` 河合英宏 / KAWAI，HIDEHIRO
2015-10-05 2:03 ` 河合英宏 / KAWAI，HIDEHIRO
2015-10-05 8:27 ` Borislav Petkov
2015-10-05 8:27 ` Borislav Petkov
2015-10-05 9:21 ` 河合英宏 / KAWAI，HIDEHIRO
2015-10-05 9:21 ` 河合英宏 / KAWAI，HIDEHIRO
2015-10-05 10:14 ` Borislav Petkov
2015-10-05 10:14 ` Borislav Petkov
2015-10-13 11:55 ` 河合英宏 / KAWAI，HIDEHIRO
2015-10-13 11:55 ` 河合英宏 / KAWAI，HIDEHIRO
2015-10-13 20:19 ` Thomas Gleixner
2015-10-14 13:54 ` Ingo Molnar
2015-10-14 13:54 ` Ingo Molnar
2015-10-16 1:58 ` 河合英宏 / KAWAI，HIDEHIRO
2015-10-16 1:58 ` 河合英宏 / KAWAI，HIDEHIRO
2015-10-13 20:22 ` Thomas Gleixner
2015-10-13 20:22 ` Thomas Gleixner
2015-10-14 3:39 ` 河合英宏 / KAWAI，HIDEHIRO
2015-10-14 3:39 ` 河合英宏 / KAWAI，HIDEHIRO
2015-10-14 7:25 ` Thomas Gleixner
2015-10-16 2:02 ` 河合英宏 / KAWAI，HIDEHIRO
2015-10-16 2:02 ` 河合英宏 / KAWAI，HIDEHIRO
2015-10-27 8:46 ` Baoquan He
2015-10-27 8:46 ` Baoquan He
2015-10-27 9:01 ` 河合英宏 / KAWAI，HIDEHIRO
2015-10-27 9:01 ` 河合英宏 / KAWAI，HIDEHIRO
2015-10-27 9:06 ` 'Baoquan He'
2015-10-27 9:06 ` 'Baoquan He'
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