bpf_cgroup_release(9)

💖 bpf_cgroup_release(9) — the Kernel API Manual, bestie edition 🎀

okay so real talk, this is bpf_cgroup_release(9) from the Kernel API Manual, and it's genuinely one of the most "hold my hand, we're letting go" functions in the whole BPF kfunc family. no cap.

✨ NAME ✨

bpf_cgroup_release — release the reference you acquired on a cgroup. that's it, that's the vibe 💅

but wait, there's a huge little asterisk here, and it's giving main character energy: if this kfunc is invoked inside an RCU read region, the cgroup is guaranteed to not be freed until the current grace period has ended — even if its refcount drops to 0. so like, you let go, but the kernel's not gonna snatch it out from under you mid-read. iconic behavior honestly. 🦋

🌸 SYNOPSIS 🌸

__bpf_kfunc void bpf_cgroup_release (struct cgroup *cgrp );

🎀 ARGUMENTS 🎀

• cgrp — the cgroup on which a reference is being released. like, the exact one you're saying bye to. don't @ the wrong one bestie 😭

💜 SEE ALSO 💜

the kernel file ./kernel/bpf/helpers.c, and literally the entire extended friend group:

• bpf_obj_new(9)
• bpf_percpu_obj_new(9)
• bpf_obj_drop(9)
• bpf_percpu_obj_drop(9)
• bpf_refcount_acquire(9)
• bpf_list_push_front(9)
• bpf_list_push_back(9)
• bpf_rbtree_add(9)
• bpf_task_acquire(9)
• bpf_task_release(9)
• bpf_cgroup_acquire(9)
• bpf_cgroup_ancestor(9)
• bpf_cgroup_from_id(9)
• bpf_task_under_cgroup(9)
• bpf_task_get_cgroup1(9)
• bpf_task_from_pid(9)
• bpf_task_from_vpid(9)
• bpf_dynptr_slice(9)
• bpf_dynptr_slice_rdwr(9)
• bpf_dynptr_copy(9)
• bpf_dynptr_memset(9)
• bpf_iter_bits_new(9)
• bpf_iter_bits_next(9)
• bpf_iter_bits_destroy(9)
• bpf_copy_from_user_str(9)
• bpf_copy_from_user_task_str(9)
• bpf_strcmp(9)
• bpf_strcasecmp(9)
• bpf_strnchr(9)
• bpf_strchr(9)
• bpf_strchrnul(9)
• bpf_strrchr(9)
• bpf_strnlen(9)
• bpf_strlen(9)
• bpf_strspn(9)
• bpf_strcspn(9)
• bpf_strstr(9)
• bpf_strcasestr(9)
• bpf_strnstr(9)
• bpf_strncasestr(9)
• bpf_lookup_user_key(9)
• bpf_lookup_system_key(9)
• bpf_key_put(9)
• bpf_verify_pkcs7_signature(9)
• bpf_task_work_schedule_signal(9)
• bpf_task_work_schedule_resume(9)
• bpf_timer_cancel_async(9)

🫶 friendly reminder: bpf_cgroup_acquire(9) is right there in the list for a reason — if you release a reference you never acquired, that's not slay, that's a bug. 😭

and that's the whole page, bestie! ✨ this little gem lives in ./kernel/bpf, dated October 2026 — write it on your arm, tell your friends, bpf_cgroup_release(9) periodt. 💖🌟💅