radix_tree_lookup(9)

📦 version 7.3.1, in nixpkgs unstable

💅 radix_tree_lookup(9) 💅

okay so this is a page from the Kernel API Manual, and bestie, it's all about radix_tree_lookup — the little function that goes "hey, what's at this index?" on a radix tree. let's get into it 🎀

✨ SYNOPSIS ✨

void * radix_tree_lookup (const struct radix_tree_root *root , unsigned
long index );

yes that's the whole signature, no cap. it hands you back a void *. 🫶

🌸 ARGUMENTS 🌸

  • root — the radix tree root. like, the actual tree you're digging around in, bestie. 🌳
  • index — the index key. this is the lil address you're asking about. 🔑

💖 DESCRIPTION 💖

so basically: look up the item at position index in the radix tree root. that's the whole vibe check. you give it a root and an index, it gives you the thing. iconic behaviour honestly. ✨

now the important bit, and I need you to listen: you can call this function under rcu_read_lock, but — and this is the big but — the caller must manage the lifetimes of leaf nodes. (eg. RCU may also be used to free them safely, which is the whole trick). 🧚

and the good news? no RCU barriers are required to access or modify the returned item. so like, you don't have to do extra ceremony for that part. we love a low-maintenance lookup. 💅

fr fr though, the lifetime management of leaf nodes is on you. the function is not gonna do it for you. main character energy means main character responsibility. 😭

🦋 SEE ALSO 🦋

Kernel file ./lib/radix-tree.c, plus this whole friend group right here — like a group chat of related functions, and yes I'm @-ing all of them:

that's the whole page, bestie, you ate it up. 🌈⭐

signing off from ./lib, dated October 2026 — stay slay, stay RCU-safe, and remember: no RCU barriers needed for that returned item 💜🎀

📦 where this page comes from