Debugging sched_ext Behavior Using the sched_ext_dump Tracepoint

Linux 6.12 shipped CONFIG_SCHED_EXT — the extensible scheduler framework that lets you swap the entire CPU scheduler at runtime using a BPF program. The power is real: custom latency profiles, workload-aware placement, NUMA-aware dispatch, all without touching kernel source. The problem is equally real: when your BPF scheduler misbehaves, tasks starve silently, CPUs park themselves for no apparent reason, and the watchdog fires a 30-second timeout with no explanation. You can’t printk from a scheduling hot path. The sched_ext_dump tracepoint is the structured way out.

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