This morning we did some routine upgrades on our server (you know, the ones Ubuntu always nags you to do). The packages that were upgraded included the kernel and Docker.
Now when we stop our Docker container with Discourse in it, it hangs in
runsv. One or more runsv processes inside the container hang, consuming 100% CPU.
top shows the CPU usage as “system” usage, so they are hung inside the kernel somewhere. Because of this, they can’t be killed even with SIGKILL; we need to reboot the server.
We’re running Ubuntu 14.04.03, 64-bit, with kernel version 3.13.0-73. The Docker version is 1.9.1.