wq_calc_pod_cpumask(9)

📦 version 7.3.1, in nixpkgs unstable

🌸 wq_calc_pod_cpumask — kernel API manual, but make it cute 🌸

okay bestie, this is wq_calc_pod_cpumask(9) from the kernel API manual — yes the whole manpage, yes we're reading it together, no you cannot skip it 💅

✨ NAME ✨

wq_calc_pod_cpumask — literally the function that calculates a wq_attrs' cpumask for a pod 🎀

✨ SYNOPSIS ✨

void wq_calc_pod_cpumask (struct workqueue_attrs *attrs , int cpu );

that's it. that's the whole signature. main character energy fr fr 👑

✨ ARGUMENTS ✨

  • attrs — the wq_attrs of the default pwq of the target workqueue. like, the actual object we're poking at 🫶
  • cpu — the target CPU. that's the CPU, bestie 🖥️✨

✨ DESCRIPTION ✨

so the whole vibe of this function: it calculates the cpumask that a workqueue with attrs should use on a pod, and the result gets stored in attrs->__pod_cpumask 💾 — that's the field, don't @ me, it really has the double underscore.

here's the tea on how it picks 🌈:

  • if pod affinity is not enabled, then attrs->cpumask is always used. like, always, no negotiations 💀
  • if pod affinity is enabled and the pod has online CPUs requested by attrs, then the cpumask it hands back is the intersection of the possible CPUs of the pod and attrs->cpumask. set math, slay 🧮✨
⚠️ and this is the part where you pay attention: the caller is responsible for ensuring that the cpumask of the pod stays stable. that's on you, bestie. it's giving "you break it you bought it" 😭🫶

✨ SEE ALSO ✨

okay so the kernel file ./kernel/workqueue.c is the mothership 🏠, and here's the entire friend group, no cap — for_each_pool(9), for_each_pool_worker(9), for_each_pwq(9), worker_pool_assign_id(9), unbound_effective_cpumask(9), get_work_pool(9), worker_set_flags(9), worker_clr_flags(9), worker_enter_idle(9), worker_leave_idle(9), find_worker_executing_work(9), move_linked_works(9), assign_work(9), kick_pool_pick(9), kick_pool(9), wq_worker_running(9), wq_worker_sleeping(9), wq_worker_tick(9), wq_worker_last_func(9), wq_node_nr_active(9), wq_update_node_max_active(9), get_pwq(9), put_pwq(9), put_pwq_unlocked(9), pwq_tryinc_nr_active(9), pwq_activate_first_inactive(9), unplug_oldest_pwq(9), node_activate_pending_pwq(9), pwq_dec_nr_active(9), pwq_dec_nr_in_flight(9), try_to_grab_pending(9), work_grab_pending(9).

the saga continues 🦋 — insert_work(9), queue_work_on(9), select_numa_node_cpu(9), queue_work_node(9), queue_delayed_work_on(9), mod_delayed_work_on(9), queue_rcu_work(9), worker_attach_to_pool(9), worker_detach_from_pool(9), create_worker(9), set_worker_dying(9), idle_worker_timeout(9), idle_cull_fn(9), maybe_create_worker(9), manage_workers(9), process_one_work(9), process_scheduled_works(9), worker_thread(9), rescuer_thread(9), check_flush_dependency(9), insert_wq_barrier(9), flush_workqueue_prep_pwqs(9), __flush_workqueue(9), drain_workqueue(9), flush_work(9), flush_delayed_work(9), flush_rcu_work(9), cancel_work_sync(9), cancel_delayed_work(9), cancel_delayed_work_sync(9).

still going, iykyk 🌸 — disable_work(9), disable_work_sync(9), enable_work(9), disable_delayed_work(9), disable_delayed_work_sync(9), enable_delayed_work(9), schedule_on_each_cpu(9), execute_in_process_context(9), free_workqueue_attrs(9), alloc_workqueue_attrs(9), init_worker_pool(9), put_unbound_pool(9), get_unbound_pool(9), apply_workqueue_attrs(9), unbound_wq_update_pwq(9), wq_adjust_max_active(9), destroy_workqueue(9), workqueue_set_max_active(9), workqueue_set_min_active(9), current_work(9), current_is_workqueue_rescuer(9), current_is_workqueue_mem_reclaim(9), workqueue_congested(9), work_busy(9), set_worker_desc(9), print_worker_info(9), show_one_workqueue(9), show_one_worker_pool(9), show_all_workqueues(9), show_freezable_workqueues(9), rebind_workers(9), restore_unbound_workers_cpumask(9), work_on_cpu_key(9).

last stretch bestie, we're so close 🔥 — freeze_workqueues_begin(9), freeze_workqueues_busy(9), thaw_workqueues(9), workqueue_unbound_housekeeping_update(9), workqueue_set_unbound_cpumask(9), workqueue_sysfs_register(9), workqueue_sysfs_unregister(9), workqueue_init_early(9), workqueue_init(9), llc_count_cores(9), llc_populate_cpu_shard_id(9), precompute_cache_shard_ids(9), workqueue_init_topology(9).

like… all of them. every single one. ate and left no crumbs 🍓👑

anyway that's the whole page 🧚 this lil cutie lives in ./kernel, and this edition is dated October 2026 — so if you're reading this from the future, hiiii, hope the cpumasks are stable 💖🦋 periodt.

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