After several hours of debugging in a larger task force yesterday and today, we finally figured out that we must have ran into an XFS bug (seems to work fine on ext4). An
ftruncate syscall hung forever and hence the process was caught in an uninterruptible sleep. This was the first time I ever witnessed
kill -9 not to “work”. But I learned a bunch of new stuff. I never dug this deep into the guts before.
Some of you probably know that
/proc/$PID/syscall tells you the current system call the process is executing. And
/proc/$PID/stack returns the kernel stack trace. Awesome stuff!
That’s a wonderful article on that matter: https://tanelpoder.com/2013/02/21/peeking-into-linux-kernel-land-using-proc-filesystem-for-quickndirty-troubleshooting/
We made a bike tour in the heat of the day. The sun was brutal with 27°C in the shade. Man, this one section was suuuuper steep and you couldn’t hill-start anymore once stopped for a quick rest, because you just spun out the tire in the loose gravel. No chance. So we had to push (I didn’t mind that, though). My mate’s battery then flattened, so he had no other choice anyways. Luckily, I have an old-school bicycle with no electronics (if you don’t count the lights). So the rest of the hills weren’t too bad for me, but he was huffing and puffing badly.
We had waffles with apple sauce for lunch at a closed ski hut out in nature. It was very peaceful, nobody around, just birds and critters. After resting a bit we tried out the scout camera. Today’s mission was to get a bit familiar with that equipment. All the pictures were taken with that DSLR, a Nikon D5200 with a 18-105mm lense. Quite a heavy rig compared to my small digicam. Looking at the pics on a big screen, we gotta keep practicing. This lense is certainly not made for macro shots. We have another one that’s probably suited for that, but I didn’t want to bring the whole bag. And more zoom would also be nice for all the birds. But we don’t have a larger zoom lense.
Finally, we encountered an old train from the Märklintage (Märklin days). This weekend they pulled out old locomotives and wagons and had extra tours between Göppingen (where Märklin, the model train manufacturer, has its headquarter) and Geislingen/Steige. Tons of people all along the tracks everywhere.