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Date: Thu, 2 Dec 2010 00:23:21 -0500
From: Don Zickus <dzickus@redhat.com>
To: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Peter Zijlstra <peterz@infradead.org>, Vivek Goyal <vgoyal@redhat.com>,
        Yinghai Lu <yinghai@kernel.org>, Ingo Molnar <mingo@elte.hu>,
        Jason Wessel <jason.wessel@windriver.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Haren Myneni <hbabu@us.ibm.com>
Subject: Re: perf hw  in kexeced kernel broken in tip
Message-ID: <20101202052321.GH18100@redhat.com>
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On Wed, Dec 01, 2010 at 01:48:07PM -0800, Eric W. Biederman wrote:
> >
> > Oh, but I'm not a device or sysdev thing, I'll never get something like
> > that.
> 
> There is also the reboot notifier, if the NMI needs to be controlled
> outside of device model.  Sigh. The NMI handling is such a special case.

I tried reboot notifiers with the nmi_watchdog and acheived some success
(on a Westmere box, a P4 still failed).  Kdump is still screwed, but maybe
we don't care for now.

Here is the quick and dirty patch I used.

Cheers,
Don


diff --git a/kernel/watchdog.c b/kernel/watchdog.c
index 792a4ed..3455cf9 100644
--- a/kernel/watchdog.c
+++ b/kernel/watchdog.c
@@ -23,6 +23,7 @@
 #include <linux/notifier.h>
 #include <linux/module.h>
 #include <linux/sysctl.h>
+#include <linux/reboot.h>
 
 #include <asm/irq_regs.h>
 #include <linux/perf_event.h>
@@ -550,6 +551,18 @@ static struct notifier_block __cpuinitdata cpu_nfb = {
 	.notifier_call = cpu_callback
 };
 
+static int __cpuinit
+reboot_callback(struct notifier_block *nfb, unsigned long action, void *unused)
+{
+	watchdog_disable_all_cpus();
+
+	return notifier_from_errno(0);
+}
+
+static struct notifier_block __cpuinitdata reboot_nfb = {
+	.notifier_call = reboot_callback
+};
+
 void __init lockup_detector_init(void)
 {
 	void *cpu = (void *)(long)smp_processor_id();
@@ -563,6 +576,7 @@ void __init lockup_detector_init(void)
 
 	cpu_callback(&cpu_nfb, CPU_ONLINE, cpu);
 	register_cpu_notifier(&cpu_nfb);
+	register_reboot_notifier(&reboot_nfb);
 
 	return;
 }