handle_lockup(9)

💅 handle_lockup(9) — the sched_ext common lockup handler, bestie

okay so this is handle_lockup, a kernel API manual page, and it's honestly kind of a big deal — it's the thing that shows up when your system is having a whole moment (stall, lockup, the works) and sched_ext needs to step in. let me walk you through it 🫶

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✨ NAME ✨

handle_lockup — the sched_ext common lockup handler. that's it, that's the vibe. she handles lockups. 💅

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🎀 SYNOPSIS 🎀

bool handle_lockup (int exit_cpu , const char *fmt , ... );

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🌸 ARGUMENTS 🌸

• exit_cpu — the CPU you want recorded in exit_info. and listen: you pass the stalled/hung CPU, not current. not current!! i cannot stress this enough, bestie 😭
• fmt — the format string. classic.
• ... — variable arguments, obviously. she's variadic, she contains multitudes ✨

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🦋 DESCRIPTION 🦋

so this gets called when the system hits a stall or lockup condition, and it kicks off an abort of sched_ext if it's enabled — which may actually resolve the reported lockup. like, the lockup might just... go away. iconic behaviour, no cap. 🔥

it returns true if sched_ext is enabled and the abort was initiated, which may resolve the lockup.

it returns false if sched_ext is not enabled, or if the abort was already initiated by someone else. like, someone else already called dibs on the abort. respect the dibs. 💀

ngl, the return value is doing double duty here — false can mean two totally different things (not enabled or already-aborted-by-someone-else), so don't assume it means just one of them, bestie.

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🌈 SEE ALSO 🌈

kernel file ./kernel/sched/ext/ext.c, plus this absolutely legendary list of friends:

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), scx_rcu_cpu_stall(9), scx_softlockup(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)

like?? that's a guest list. every single one of them, periodt. 👑

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and that's the whole page, bestie — this one lives in ./kernel/sched/ext and the docs are dated October 2026. go forth and lock up (responsibly) 💖✨🎀🌟🦋