[SOLVED] How to investigate reboot PI 2

by **jft** » Thu Nov 12, 2015 5:20 pm

My PI 2 reboots randomly when I'm running an opengl app.

Now I know this is probably due to something going wrong in the app but I was wondering how best to try and debug this.

Currently I get no error messages in systemd or dmesg. All I get is a reboot message.

The fact that reboot is being written into the log surely means the kernel knows something has happened!

Temperature immediately afer the crash was 40C so don't think its that.

Power is from a UPS so I dont think its that (If I don't run the graphics app it will run for days without rebooting)

The SD Card is a high quality one and again runs for days if not running the graphics app.

The app just draws a texture and a few lines on the screen so nothing heavy. Note that I'm not running X-Windows or anything like that.

Kernel version is 4.1.12-2 (latest afaik) I've also tried it on 4.1.7-2

Is there any kind of driver monitoring I can enable so I could debug what the display driver is doing before the crash?

Cheers

by **WarheadsSE** » Thu Nov 12, 2015 6:34 pm

What is doing the DC input to the Pi?

by **jft** » Thu Nov 12, 2015 6:59 pm

Well it is behind a UPS and will happily carry on working on the UPS for about 8 hours after power is cut. However I can log the internal voltages using the vcgencmd tools and see if it drops just before a reboot. Although whether the drop will be written to the logs in time is an issue. Unfortunately its one of those problems that can take from 5min - 48 hours to appear.

by **WarheadsSE** » Thu Nov 12, 2015 8:25 pm

What is your power supply that provides the actual DC power to the Pi?

by **jft** » Thu Nov 12, 2015 8:55 pm

Its a Puls unit 240 -> 24V supply to a a voltage / battery charger circuit then to the PI. The voltage circuit limits the incoming supply to 5V. I also have the same thing from a PI powered directly by a Circuit Specialist bench supply at 5V.

If I cut the power supply then the battery takes over and goes through the same voltage circuit limiting to 5V. I can switch between the two while the app is running without any issues.

Incidently it just failed. Temp was at 42.7 volts 1.2V and steady.

If it was a display driver issue would I expect to see kernel panic messages then? Is the only way to get just a reboot message if its a power issue? Do you know where I can find out exactly where the reboot message is written to the log in the kernel?

---
I've just rigged it up directly to the bench supply now as well.
Currently set to 5V and the PI is drawing 0.57A

by **jft** » Mon Nov 16, 2015 8:51 am

This turned out to be a Ground loop with the screen that I was using. After removing an inch of the screening from the HDMI cable near the PI the system has been running fine with no reboots for the last 3 days.