Re: perf hw in kexeced kernel broken in tip

Don Zickus
2010-12-02T05:23:44Z

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;
}