watchdog: Don't throttle the watchdog

Stephane reported that when the machine locks up, the regular ticks,
which are responsible to resetting the throttle count, stop too.

Hence the NMI watchdog can end up being throttled before it reports on
the locked up state, and we end up being sad..

Cure this by having the watchdog overflow reset its own throttle count.

Reported-by: Stephane Eranian <eranian@google.com>
Tested-by: Stephane Eranian <eranian@google.com>
Cc: Don Zickus <dzickus@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1282215916.1926.4696.camel@laptop>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

diff --git a/kernel/watchdog.c b/kernel/watchdog.c
index 613bc1f046108ec52b8f7372fe2e7e66aa8fe4c7..0d53c8e853b12450cf0c74665d13a22e91a47543 100644 (file)
--- a/kernel/watchdog.c
+++ b/kernel/watchdog.c
@@ -206,6 +206,9 @@ void watchdog_overflow_callback(struct perf_event *event, int nmi,
                 struct perf_sample_data *data,
                 struct pt_regs *regs)
 {
+       /* Ensure the watchdog never gets throttled */
+       event->hw.interrupts = 0;
+
        if (__get_cpu_var(watchdog_nmi_touch) == true) {
                __get_cpu_var(watchdog_nmi_touch) = false;
                return;