scx_softlockup(9)

💅 scx_softlockup(9) 💅

Okay bestie, welcome to the Kernel API Manual page for scx_softlockup — the sched_ext softlockup handler. This is highkey emergency-scheduler content, so hydrate and pay attention. 💖

🎀 NAME 🎀

scx_softlockup — sched_ext softlockup handler. That’s the whole vibe of the name section, periodt. ✨

✨ SYNOPSIS ✨

void scx_softlockup (u32 dur_s );

🌸 ARGUMENTS 🌸

• dur_s — the number of seconds of CPU stuck due to soft lockup. Basically the stuck-o-meter reading, ngl. 🕰️

🦋 DESCRIPTION 🦋

On some multi-socket setups (e.g. 2x Intel 8480c), the BPF scheduler can live-lock the system by making many CPUs target the same DSQ to the point where soft-lockup detection triggers. Not me learning that many CPUs can all pile onto the same DSQ and just… create chaos. 😭

This function is called from the soft-lockup watchdog when the triggering point is close, and it tries to unjam the system and abort the BPF scheduler. It’s literally the “bestie, we need to get out of this situation” function. 🔥

💜 SEE ALSO 💜

The kernel file is ./kernel/sched/ext/ext.c — that’s the home base 🏠 — and here’s the full friend group, no cap:

• scx_is_descendant(9), rq_is_open(9), scx_fill_cmask_scratch(9), scx_call_op_set_cpumask(9)
• nldsq_next_task(9), nldsq_cursor_next_task(9), nldsq_cursor_lost_task(9), scx_task_iter_start(9)
• scx_task_iter_unlock(9), scx_task_iter_relock(9), scx_task_iter_stop(9), scx_task_iter_next(9)
• scx_task_iter_next_locked(9), scx_dump_event(9), wait_ops_state(9), scx_cpu_valid(9)
• schedule_deferred(9), schedule_deferred_locked(9), dsq_insert_head(9), set_task_slice_keep_oob(9)
• scx_task_slice_ended(9), move_remote_task_to_local_dsq(9), unlink_dsq_and_switch_rq_lock(9), move_task_between_dsqs(9)
• dispatch_to_local_dsq(9), finish_dispatch(9), scx_prio_less(9), __scx_init_task(9)
• task_dead_and_done(9), scx_tg_sched(9), scx_tg_knob_sched(9), handle_lockup(9)
• scx_rcu_cpu_stall(9), scx_hardlockup(9), unbypass_renotify_idle(9), scx_bypass(9)
• scx_propagate_exit_irq_workfn(9), scx_flush_disable_work(9), print_scx_info(9), scx_bpf_dsq_insert___v2(9)
• __scx_bpf_dsq_insert_vtime(9), scx_bpf_dispatch_nr_slots(9), scx_bpf_dispatch_cancel(9), scx_bpf_dsq_move_to_local___v2(9)
• scx_bpf_dsq_move_set_slice(9), scx_bpf_dsq_move_set_vtime(9), scx_bpf_dsq_move(9), scx_bpf_dsq_move_vtime(9)
• scx_bpf_reenqueue_local(9), scx_bpf_create_dsq(9), scx_bpf_task_set_slice(9), scx_bpf_task_set_dsq_vtime(9)
• scx_bpf_kick_cpu(9), scx_bpf_kick_cid(9), scx_bpf_dsq_nr_queued(9), scx_bpf_destroy_dsq(9)
• bpf_iter_scx_dsq_new(9), bpf_iter_scx_dsq_next(9), bpf_iter_scx_dsq_destroy(9), scx_bpf_dsq_peek(9)
• scx_bpf_dsq_reenq(9), scx_bpf_reenqueue_local___v2(9), scx_bpf_exit_bstr(9), scx_bpf_error_bstr(9)
• scx_bpf_dump_bstr(9), scx_bpf_cpuperf_cap(9), scx_bpf_cidperf_cap(9), scx_bpf_cpuperf_cur(9)
• scx_bpf_cidperf_cur(9), scx_bpf_cpuperf_set(9), scx_bpf_cidperf_set(9), scx_bpf_nr_node_ids(9)
• scx_bpf_nr_cpu_ids(9), scx_bpf_nr_cids(9), scx_bpf_nr_online_cids(9), scx_bpf_online_cmask(9)
• scx_bpf_this_cid(9), scx_bpf_get_possible_cpumask(9), scx_bpf_get_online_cpumask(9), scx_bpf_put_cpumask(9)
• scx_bpf_task_running(9), scx_bpf_task_cpu(9), scx_bpf_task_cid(9), scx_bpf_locked_rq(9)
• scx_bpf_cpu_curr(9), scx_bpf_cid_curr(9), scx_bpf_tid_to_task(9), scx_bpf_now(9)
• scx_bpf_events(9), scx_bpf_task_cgroup(9)

Signed, sealed, delivered by ./kernel/sched/ext — October 2026 — scx_softlockup(9) 💌