Re: NMI watchdog

[John Sigler <linux.kernel@free.fr>]

Steven Rostedt wrote:

> John Sigler wrote:
>
> > I'm experiencing a full system lockup. I'm using an out-of-tree driver
> > which I suspect is responsible. I'm trying to enable the NMI watchdog.
> >
> > # cat /proc/version
> > Linux version 2.6.22.1-rt9 (gcc version 3.4.6) #1 PREEMPT RT Tue Oct 9
> > 12:25:47 CEST 2007
> >
> > # cat /proc/cmdline
> > ro root=/dev/hdc1 console=ttyS0,57600n8 console=tty0 panic=3 apic=debug
> > nmi_watchdog=2
>
> I've noticed on some boxes that nmi_watchdog=2 does what you state. Try
> out nmi_watchdog=1.

# diff boot_message013 boot_message014
49c49
< Kernel command line: ro root=/dev/hdc1 console=ttyS0,57600n8 
console=tty0 panic=3 apic=debug nmi_watchdog=2
---
> Kernel command line: ro root=/dev/hdc1 console=ttyS0,57600n8 
console=tty0 panic=3 apic=debug nmi_watchdog=1
69c69
< Calibrating delay using timer specific routine.. 4802.79 BogoMIPS 
(lpj=24013960)
---
> Calibrating delay using timer specific routine.. 4802.80 BogoMIPS 
(lpj=24014009)
88a89
> activating NMI Watchdog ... done.
97c98
< ..... CPU clock speed is 2400.1215 MHz.
---
> ..... CPU clock speed is 2400.1221 MHz.
98a100
> APIC timer registered as dummy, due to nmi_watchdog=1!
213a216,217
> Clockevents: could not switch to one-shot mode: lapic is not functional.
> Could not switch to high resolution mode on CPU 0

Do you know why nmi_watchdog=1 disables high-resolution timers?

And why nmi_watchdog=1 implies APIC timer registered as dummy?

# cat /sys/devices/system/clocksource/clocksource0/available_clocksource
tsc acpi_pm pit jiffies

# cat /sys/devices/system/clocksource/clocksource0/current_clocksource
tsc

# cat /proc/timer_list
Timer List Version: v0.3
HRTIMER_MAX_CLOCK_BASES: 2
now at 4613373211613 nsecs

cpu: 0
 clock 0:
  .index:      0
  .resolution: 10000000 nsecs
  .get_time:   ktime_get_real
  .offset:     0 nsecs
active timers:
 clock 1:
  .index:      1
  .resolution: 10000000 nsecs
  .get_time:   ktime_get
  .offset:     0 nsecs
active timers:
 #0: <cf2c1ec0>, it_real_fn, S:01
 # expires at 4630663830511 nsecs [in 17290618898 nsecs]
  .expires_next   : 9223372036854775807 nsecs
  .hres_active    : 0
  .nr_events      : 0
  .nohz_mode      : 0
  .idle_tick      : 0 nsecs
  .tick_stopped   : 0
  .idle_jiffies   : 0
  .idle_calls     : 0
  .idle_sleeps    : 0
  .idle_entrytime : 0 nsecs
  .idle_sleeptime : 0 nsecs
  .last_jiffies   : 0
  .next_jiffies   : 0
  .idle_expires   : 0 nsecs
jiffies: 431306


Tick Device: mode:     0
Clock Event Device: pit
 max_delta_ns:   27461866
 min_delta_ns:   12571
 mult:           5124677
 shift:          32
 mode:           2
 next_event:     9223372036854775807 nsecs
 set_next_event: pit_next_event
 set_mode:       init_pit_timer
 event_handler:  tick_handle_periodic_broadcast
tick_broadcast_mask: 00000001
tick_broadcast_oneshot_mask: 00000000


Tick Device: mode:     0
Clock Event Device: lapic
 max_delta_ns:   1006581321
 min_delta_ns:   1799
 mult:           35793226
 shift:          32
 mode:           1
 next_event:     0 nsecs
 set_next_event: lapic_next_event
 set_mode:       lapic_timer_setup
 event_handler:  tick_handle_periodic

# cat /proc/interrupts
           CPU0
  0:     468721   IO-APIC-edge      timer
  4:        326   IO-APIC-edge      serial
  8:          1   IO-APIC-edge      rtc
  9:          0   IO-APIC-fasteoi   acpi
 15:      15964   IO-APIC-edge      ide1
 16:       4217   IO-APIC-fasteoi   eth0
 17:       2340   IO-APIC-fasteoi   eth1
 18:       2340   IO-APIC-fasteoi   eth2
 19:       2340   IO-APIC-fasteoi   eth3
NMI:     468690
LOC:          0
ERR:          0
MIS:          0

Regards.
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