hlist_nulls_add_tail_rcu(9)

📦 version 7.3.1, in nixpkgs unstable

💅 hlist_nulls_add_tail_rcu(9) 💅

okay so this is a page from the Kernel API Manual and honestly it's short but it's mighty — we're talking about hlist_nulls_add_tail_rcu, bestie. buckle up 🎀

✨ NAME ✨

hlist_nulls_add_tail_rcu — and that's it, that's the whole description. the original literally leaves it blank 😭 which is giving "the function name IS the description" energy. iconic of it, honestly.

🌸 SYNOPSIS 🌸

void hlist_nulls_add_tail_rcu (struct hlist_nulls_node *n , struct
hlist_nulls_head *h );

that's the whole signature, no cap — void return, two pointers, one vibe. 🦋

💖 ARGUMENTS 💖

  • n — the element you're adding to the hash list. this is the little guy going in 🫶
  • h — the list you're adding it to. this is the destination, the main character energy list itself 👑

🔥 DESCRIPTION 🔥

so what does it do? it adds the specified element to the specified hlist_nulls, while permitting racing traversals. yes, "racing traversals" — it's giving multitasking queen 🏎️✨

now here's the important part, bestie, listen up 🙈: the caller must take whatever precautions are necessary (such as holding appropriate locks) to avoid racing with another list-mutation primitive — things like hlist_nulls_add_head_rcu or hlist_nulls_del_rcu — running on this same list. like, that's on you, not on the function. do not @ me.

however — and this is the slay part — it is perfectly legal to run concurrently with the _rcu list-traversal primitives, such as hlist_nulls_for_each_entry_rcu, which exist to prevent memory-consistency problems on Alpha CPUs. yes, those Alpha CPUs. they know what they did 💀

and regardless of the type of CPU — Alpha or not, bestie — the list-traversal primitive must be guarded by rcu_read_lock. no exceptions, periodt. 🔒

⚠️ quick vibe check: mutation ≠ traversal. your other mutation primitives need locks because they can race with you. your _rcu traversals are chill to run alongside you, but they gotta be wrapped in rcu_read_lock. don't mix these up or it's gonna be a bad time 😭

🌈 SEE ALSO 🌈

the whole nulls-rcu friend group, all here, all invited to the group chat 🫶💜

🧚 sign-off 🧚

this absolute banger lives in ./include/linux, dated October 2026, and yes the footer still says hlist_nulls_add_tail_rcu(9) because it knows exactly who it is 💅✨

go forth and add things to the tail, bestie — with locks, and with love. 🎀⭐

📦 where this page comes from