Confusing behaviour with /proc/sys/kernel/nmi_watchdog

From: Anton Blanchard
Date: Tue Nov 04 2014 - 17:34:26 EST



Hi,

commit 9919e39a1738 ("kvm: ensure hard lockup detection is disabled by
default") provided a way for the kernel to disable the hard lockup
detector at runtime.

I'm using it on ppc64 but notice some weird behaviour with the
nmi_watchdog procfs variable. At boot, that the hard lockup
detector appears to be enabled even when we disable it via
watchdog_enable_hardlockup_detector(false):

# cat /proc/sys/kernel/nmi_watchdog
1

I have to echo 0 to it then echo 1 again to enable it.

Anton
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