hlist_del_rcu(9)

📦 version 7.3.1, in nixpkgs unstable

💖 hlist_del_rcu 💖

okay so bestie, welcome to the Kernel API Manual (section 9, yes it's giving very official) — this one's about deletes entry from hash list without re-initialization. slay, let's get into it 🎀

✨ SYNOPSIS ✨

void hlist_del_rcu (struct hlist_node *n );

literally the whole signature, no cap 🫶

🌸 ARGUMENTS 🌸

  • n — the element to delete from the hash list. that's the one, the main character of this operation 👑

🎀 NOTE 🎀

okay this part is important, listen up 🙈

list_unhashed on entry does not return true after this — the entry is left in an undefined state. ngl that sounds scary but it's actually the whole point: it's useful for RCU based lockfree traversal ✨

In particular, it means that we can not poison the forward pointers that may still be used for walking the hash list. like, we just can't, they're still out there being used 💀

The caller must take whatever precautions are necessary (such as holding appropriate locks) to avoid racing with another list-mutation primitive, such as hlist_add_head_rcu or hlist_del_rcu, running on this same list.

that's the "you're on your own for locking, bestie" clause 🫶

But — and this is the iconic part — it is perfectly legal to run concurrently with the _rcu list-traversal primitives, such as hlist_for_each_entry. yes queen, concurrent read while you delete, that's the vibe check passing 🌈

💅 SEE ALSO 💅

Kernel file ./include/linux/rculist.h, plus this whole friend group right here:

that's the whole page, bestie, you ate it 🍓

source dir ./include/linux · dated October 2026 · mwah 💋 go forth and traverse safely 🦋

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