Debugging crashes

[Wogwai]

I had a ticket open on askubuntu - but it looks like it's on hold. So I'll ask it here.

http://askubuntu.com/questions/475795/how-to-debug-a-fatal-system-crash?noredirect=1#comment634641_475795

I'm getting seemingly random fatal system freezes that require me to rebook whilst playing DOTA2. Obviously this is quite disruptive for my match and teamates so I'd really like to debug.

I'm currently experimenting with putting sdout into a desktop log file - however as crashes can be a few days in between it's taking me a while to capture data.

Does anyone know if:

1) steam keeps logs on linux
2) if there is already an effective workflow to debug a game crash
3) if perhaps I can launch a game via terminal and track + log DOTA2 specific log events instead of steam more generally.

Any help would be much appreciated!

[Kranky K. Krackpot]

The logs are in /tmp/dumps
It's possible to run Steam with GDB or strace like "STEAM_DEBUGGER=gdb steam"
To debug a game with GDB -- "GAME_DEBUGGER=gdb steam"
There're also LD_DEBUG and some more env vars, but I can't remember exactly right now.

[Ashley]

I don't know how to make a terminal output to a file but if you start Steam from terminal it'll output everything (even from games).
You could close out of Steam completely and run

$ steam steam://run/570

and it'll do exactly what you want. (570 is Dota 2's appid)
But I really have no idea if you'll get anything you can debug with, you don't have the source code for Dota 2 to begin with, and even then it sounds like an issue with your specific setup causing problems for the game rather than the game by itself.

[THINOUS]

I have the same problem

[Mika]

Here's how to make log file of the terminal session... http://askubuntu.com/questions/161935/how-do-i-log-all-input-and-output-in-a-terminal-session
Use the "script" command, before starting steam from terminal.

[Kranky K. Krackpot]

Originally posted by Mika:

Here's how to make log file of the terminal session... http://askubuntu.com/questions/161935/how-do-i-log-all-input-and-output-in-a-terminal-session
Use the "script" command, before starting steam from terminal.

all terminal output already goes to /tmp/dumps/*_stdout.txt

[Wogwai]

Many thanks all, I will try a few of the suggestions and report back

[Wogwai]

here's the pasebin from my /tmp/dumps/

anyone see anything out of the ordinary?

http://pastebin.com/QzXzZep2

[Ashley]

Originally posted by Ouiroh:

here's the pasebin from my /tmp/dumps/

anyone see anything out of the ordinary?

http://pastebin.com/QzXzZep2

Did it crash?

(process:4073): GLib-CRITICAL **: g_slice_set_config: assertion 'sys_page_size == 0' failed
NOTE: child process received `Goodbye', closing down

doesn't look normal..

[Kranky K. Krackpot]

Originally posted by Ouiroh:

here's the pasebin from my /tmp/dumps/

anyone see anything out of the ordinary?

http://pastebin.com/QzXzZep2

What exactly you tried to do and what happened? You played Dota and it froze or crashed? The log doesn't look much like that. What is you videocard and what Steam says about it in Help -> System Information? There must be lines there something like this:

Video Card:
Driver: NVIDIA Corporation GeForce GTX 660/PCIe/SSE2
Driver Version: 4.4.0 NVIDIA 334.21
OpenGL Version: 4.4
...

Do you have more logs in /tmp/dumps?
BTW, if Dota freezes you can switch to terminal CTRL-ALT-F1, log in, kill the app from there and when switch back to X with CTRL-ALT-F7.

[Wogwai]

Yes I guess you'll need more info. Here'es the details.

The bug is irregular, it does not happen every game - nor consistantly with a character / level of activity / combination of skills and or particle effects as a far as I can tell.

On occasion that it does happen it seems more likely to happen more than once in the course of a single match.

The effect causes the screen to lock, looping the last ~.25 second of sound and then hangs. I have waited for the effect to dissapate for about 1 min previosuly but to no effect - I tend to want to get back in the dota game.

As far as I can tell, when this occurs the entire system has died - no combination of keys has ever logged me out, shifted the window or returned me to desktop - leaving a hard reboot as the only recourse. I have not observed this with any other game (i have used this computer since October mainly on less demanding games but I've sucessfully played the likes of Metro with no similar problems).

Additionally and worth noting - I'm on Ubuntu 14.04, I have an ATI graphics card and the machine is self built.

This leaves as likely candidates that:

1) perhaps my powersupply is failing to deliver the goods
2) there is an issue with the ATI Catalyst drivers
3) there is a steam bug
4) there is a linux bug.

The askUbuntu forums were unhelpful in delievering further info about how to effectivly log a problem in a way that would help me isolate and strike one or two of those causes off the list.

I agree:

(process:4073): GLib-CRITICAL **: g_slice_set_config: assertion 'sys_page_size == 0' failed
NOTE: child process received `Goodbye', closing down

does not look good however frustratingly these logs are not timestamped so I can't tell when that occured - it may have been a slightly less fatal steam crashing to desktop whilst I was browsing the store - rather than a fatal DOTA Crash.

Many thanks for the assistance so far - I've appreciated the readiness of these forums to get back with a response!

[Cybertao]

It's your hardware or the graphics driver. Logs files won't help as they don't work when the system locks up, you might be lucky and some related event get's logged before the system goes down - you will need to look at the system log though, not Steam's or the game's.
Ultimately you need to listen to the kernel log output over serial or ethernet port.

[Wogwai]

How would I go about doing that?

[Cybertao]

This covers the system log files:
https://help.ubuntu.com/community/LinuxLogFiles

The kernel documentation covers listening to debug output:
https://www.kernel.org/doc/Documentation/serial-console.txt
https://www.kernel.org/doc/Documentation/networking/netconsole.txt

[Kranky K. Krackpot]

So, even CTRL-ALT-F1 doesn't work, and ALT-SysRq-B either? Wow...
Have a look http://www.howtogeek.com/119127/use-the-magic-sysrq-key-on-linux-to-fix-frozen-x-servers-cleanly-reboot-and-run-other-low-level-commands/
I agree with Cybertao that the issue looks very like a problem with video driver. Or with DE, I'd add. Maybe you need to disable compositing or enable it or like that. On pastebin I can't see anything special: game started, game stopped, that's all.
System logs https://help.ubuntu.com/community/LinuxLogFiles You need last lines from kernel ring buffer (dmesg), system log, and X11 log.
BTW, as they suggested on askubuntu, you can try to redirect steam's output into a separate file "steam > steam.log 2>&1", so that it might survive reboot. After that look for steam.log file in your home dir.
Serial or ethernet debugging requires 2 PCs -- one to run Dota, and another to read the first's messages. It's not very difficult, but might be tricky if you never did it before. Anyway, personally I still don't believe that it's Dota locks CPU. For me it looks more like Dota (process) crashes, but its so to say "picture" stays on screen so it's not possible to see anything behind it.
What if you lower graphics settings?

[Wogwai]

Hi Kranky, Many thanks I did that - re: "Steam > steam.log 2>&1" and that's the source of the pastebinb entry. I'm gonna try lowering the settings will report back across the next week if anything changes.

Thanks for all the support!