x86/nmi: Enable panic() when NMI handler runs too long

Firmware, device-driver, and configuration issues can result in
long-running NMI handlers, for example, nmi_cpu_backtrace_handler()
running for more than two seconds, and with no console issues.  In this
case, this is not the fault of nmi_cpu_backtrace_handler(), but it is
the first symptom of the underlying problem.  These NMI handlers result
in various other problems, including CSD-lock warnings, clocksource
watchdog false positives, scheduler frequency invariance wobbliness,
systemd excessive-CPU complaints, and even the occasional RCU CPU
stall warning.  Eventually, the automation will take the system out of
service, but with quite a bit of noise obscuring the underlying issue,
and thus confusing both automation and human beings.

Therefore, provide a toolong_nmi_panic __setup() parameter that makes
nmi_check_duration() invoke nmi_panic() if the just-completed NMI handler
ran for more than the specified number of milliseconds.  This parameter
defaults to zero, which disables the nmi_panic().  As in, by default
you get the same behavior that you get today.

[ paulmck: Apply kernel test robot feedback. ]

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Cc: Thomas Gleixner <tglx@kernel.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: <x86@kernel.org>

0 files changed, 0 insertions, 0 deletions