Watchdog and Processor C-States [solved]

[bugmenot]

Hello,
I'm using the 2.6.37 kernel and i've enabled the watchdog in the bios and set it to 120 seconds.
Moreover i'm using the software "watchdog" from watchdog.sf.net to trigger it every 20 seconds (interval = 20 in /etc/watchdog.conf).
Still, the hardware watchdog was triggered after some random period of time when idling.

[Solution]
With the help of Mylife and Dennis the culprit was found: There seems to be a bug when the processor idles in C6.
So, you could either disable C-States completely by setting the "Processor Full Speed" variable in the BIOS to "GV3 only", or you could disable the C-State C6 via a kernel cmdline flag: "intel_idle.max_cstate=4".
I choose the latter, because it consumes a bit less energy.

[bugmenot]

Update:
It doesn't have to do anything with the auto-suspend of usb. Any other ideas?

The reset doesn't come regularly either. Sometimes after 4 Minutes, sometimes it needs 20...

[Mylife]

Hi,

What if setting "Processor Full Speed" to "GV3 Only" in the BIOS?

(I'm not a specialist at all... sorry if I'm totally out of the field).

[Denis]

Hi,
The basic watchdog usage:

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sudo modprobe sbc_fitpc2_wdt margin=60
sudo touch /dev/watchdog
# now watchdog is enabled. fitPC2 will be rebooted after 60 sec.
sudo echo V > /dev/watchdog
# now watchdog is disabled. fitPC2 will not be rebooted.

Test this to see watchdog indeed working. See dmesg output.

I think you have wrong watchdog configuration, may be some daemon missing or bug in watchdog.sf.net itself.

[bugmenot]

Hello MyLife and Dennis,
Setting the Processor Full Speed setting to GV3 seemed to help. But i really don't want to do that the whole time, since the fit-pc2i will idle a lot and as far as i understand it C-states will save more power.

Dennis, you're the author of the driver, right? The watchdog daemon works. And i tried something similar too ("cat > /dev/watchdog", then typing something and then wait one minute for the reset).

So right now i think that the watchdog hardware/driver don't work properly with the processor state C6. I'm running a test now where i limited the kernel to C4 by adding intel_idle.max_cstate=4 to the kernel cmdline.

[Mylife]

According to Irads:

Disabling C-States has no effect on power when the computer is under load. It consumes about 1W more when the computer idles.

See: http://www.fit-pc2.com/forum/viewtopic. ... =GV3#p8331
Do you really care about this lonely Watt ?

[bugmenot]

Do you really care about this lonely Watt ?

Well, it's 1/8th or so. Of course, it doesn't make that much sense - anyway, the geek in me can't live with wakeups-from-idle/s of more than 50 when idling, which was the case for GV3.

With the above mentioned kernel cmdline flag the hardware watchdog doesn't reset the board anymore. It's running since hours with 1.7 wakeups-from-idle/s, nearly all the time in C4.

Case closed. And i'm only 'wasting' 80mW instead of 1 W
http://software.intel.com/en-us/article ... atforms-2/ .

[Mylife]

I'm impressed !

[hackeron]

I have GV3 Only set in bios (is this still required?) and have the watchdog enabled in bios and set to 251 seconds.

I am then following the instructions:

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sudo modprobe sbc_fitpc2_wdt margin=60
sudo touch /dev/watchdog

I am seeing this in syslog:

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Jan 10 15:17:54 OracleBMW1 kernel: [   80.906485] sbc_fitpc2_wdt WATCHDOG: SBC-FITPC2 found
Jan 10 15:17:59 OracleBMW1 kernel: [   85.908225] sbc_fitpc2_wdt WATCHDOG: Device closed unexpectedly - timer will not stop

Sure enough, 3 or so minutes later, it reboots :/

Any ideas? - I'm on ubuntu 12.04