cgroup_css_set_fork(9)

🌸 cgroup_css_set_fork(9) — NAME 🌸

okay so this page is from the Kernel API Manual, and it’s literally about finding or creating a css_set for a child process. bestie, it’s giving “where does this baby process belong in cgroup land” energy 💅

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✨ SYNOPSIS ✨

int cgroup_css_set_fork (struct kernel_clone_args *kargs );

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💅 ARGUMENTS 💅

• kargs — the arguments passed to create the child process 🫶

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🦋 DESCRIPTION 🦋

so here’s the tea: this function finds or creates a new css_set that the child process will be attached to in cgroup_post_fork. by default, the child process gets the same css_set as its parent — copy/paste energy, no cap 😌

if CLONE_INTO_CGROUP is specified, this function tries to find an existing css_set that includes the requested cgroup, and if it doesn’t find one, it creates a new css_set that the child will be attached to later. if this function succeeds, it will hold cgroup_threadgroup_rwsem on return 🫡

and if CLONE_INTO_CGROUP is requested, this function will grab the cgroup mutex before grabbing cgroup_threadgroup_rwsem, and it will hold a reference to the target cgroup. like, it’s not just vibing — it’s holding onto stuff 🔥

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🔥 SEE ALSO 🔥

over in the kernel file ./kernel/cgroup/cgroup.c, the whole cgroup friend group is linked here — peek these, iykyk:

• 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_calc_subtree_ss_mask(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_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)

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this lil page is sourced from ./kernel/cgroup, dated October 2026, and you’re reading cgroup_css_set_fork(9) in the Kernel API Manual — periodt, mwah 💜🎀