cgroup_calc_subtree_ss_mask(9)

🎀 cgroup_calc_subtree_ss_mask(9) 🎀

okay bestie so this is a page from the Kernel API Manual and it's literally all about one little function that does the math on your cgroup subsystem masks. no cap, it's short but it matters. let's get into it 💅

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✨ NAME ✨

cgroup_calc_subtree_ss_mask — calculate subtree_ss_mask

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🌸 SYNOPSIS 🌸

u32 cgroup_calc_subtree_ss_mask (u32 subtree_control , u32 this_ss_mask
);

yes queen, that's a u32 coming in and a u32 going out. two args, one vibe 🦋

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💖 ARGUMENTS 💖

• subtree_control — the new subtree_control mask you're trying to consider. this is the one you wanna apply, the main character of the argument list 👑
• this_ss_mask — the available subsystems. basically the guest list for the party — only these ones are allowed in ✨

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🧚 DESCRIPTION 🧚

so listen. on the default hierarchy, a subsystem can be all "hey, I'm not going anywhere unless my friends come too" and request that other subsystems get enabled along with it — it does this through its ->depends_on mask. super codependent, we love it 🫶

because of that, the number of subsystems that end up enabled can be bigger than whatever you actually spelled out in "cgroup.subtree_control". like it's giving "you brought the whole friend group to the function" energy. 💀

so what this function does is figure out exactly which subsystems need to be enabled if subtree_control is to be applied while restricted to this_ss_mask. that's it, that's the job. it does the math so you don't have to 🧮✨

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🔥 SEE ALSO 🔥

lowkey a whole syllabus down here, but every single one of these is family so here we go:

• kernel file ./kernel/cgroup/cgroup.c
• cgroup_ssid_enabled(9), cgroup_on_dfl(9), cgroup_e_css_by_mask(9), cgroup_e_css(9)
• cgroup_get_e_css(9), __cgroup_task_count(9), cgroup_task_count(9), for_each_css(9)
• do_each_subsys_mask(9), css_set_populated(9), css_update_populated(9), css_set_update_populated(9)
• css_set_move_task(9), compare_css_sets(9), find_existing_css_set(9), allocate_cgrp_cset_links(9)
• link_css_set(9), find_css_set(9), cgroup_file_mode(9), cgroup_kn_unlock(9)
• cgroup_kn_lock_live(9), css_clear_dir(9), css_populate_dir(9), cgroup_attach_lock(9)
• cgroup_attach_unlock(9), cgroup_migrate_add_task(9), cgroup_taskset_first(9), cgroup_taskset_next(9)
• cgroup_migrate_execute(9), cgroup_migrate_vet_dst(9), cgroup_migrate_finish(9), cgroup_migrate_add_src(9)
• cgroup_migrate_prepare_dst(9), cgroup_migrate(9), cgroup_attach_task(9), cgroup_update_dfl_csses(9)
• cgroup_lock_and_drain_offline(9), cgroup_save_control(9), cgroup_propagate_control(9), cgroup_restore_control(9)
• cgroup_apply_control_enable(9), cgroup_apply_control_disable(9), cgroup_apply_control(9), cgroup_finalize_control(9)
• cgroup_enable_threaded(9), cgroup_tryget_css(9), cgroup_addrm_files(9), cgroup_rm_cftypes(9)
• cgroup_add_cftypes(9), cgroup_add_dfl_cftypes(9), cgroup_add_legacy_cftypes(9), cgroup_file_notify(9)
• cgroup_file_show(9), css_next_child(9), css_next_descendant_pre(9), css_rightmost_descendant(9)
• css_next_descendant_post(9), css_has_online_children(9), css_task_iter_advance_css_set(9), css_task_iter_start(9)
• css_task_iter_next(9), css_task_iter_end(9), css_create(9), kill_css_sync(9)
• kill_css_finish(9), cgroup_destroy_locked(9), cgroup_init_early(9), cgroup_init(9)
• cgroup_fork(9), cgroup_v1v2_get_from_file(9), cgroup_get_from_file(9), cgroup_css_set_fork(9)
• cgroup_css_set_put_fork(9), cgroup_can_fork(9), cgroup_cancel_fork(9), cgroup_post_fork(9)
• cgroup_task_exit(9), css_tryget_online_from_dir(9), css_from_id(9), cgroup_get_from_path(9)
• cgroup_v1v2_get_from_fd(9), cgroup_get_from_fd(9), cgroup_parse_float(9)

iykyk, that's the whole cgroup cinematic universe right there 🌈👑

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ok that's genuinely the whole page bestie, no cap, nothing hidden. go forth and calculate those masks 💜

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~mwah~ this lil page lives in ./kernel/cgroup and it's dated October 2026, so it's ✨current✨ — see u in the source tree, babe 🍓💅