[tetha]

But it did not take 2 threads within the same application to interact in a bad way on data the system controlled to cause this problem.

This reads more like an overly broad transition in a deterministic state machine. The fix was to split up a bad transition to shutdown.

[microgpt]

Concurrency bugs don't have to be within a single process.

[inexcf]

By that definition, every write() call that doesn't check for EAGAIN is a concurrency bug you're racing the disk controller. The term stops meaning anything.