Searching for the cause of hung tasks in the Linux kernel

This post explains how Linux detects and reports hung tasks, how to tune related sysctls, and how to troubleshoot real-world causes using kernel logs, stack traces, and tools like bpftrace and drgn. Through examples (filesystem workqueue pressure, coredump-induced blocking, and RTNL mutex contention involving calico-node/WireGuard), it shows that hung task warnings often flag symptoms rather than root causes and provides practical guidance for isolating offenders and improving observability.