seq_hlist_start_rcu(9)

📦 version 7.3.1, in nixpkgs unstable

💖 seq_hlist_start_rcu 💖

okay so bestie, welcome to the Kernel API Manual — yes that's the manual name, and yes this page lives in it. today's main character is seq_hlist_start_rcu, and it's genuinely one of those little functions that makes a whole traversal possible. let's go 🎀

✨ NAME ✨

seq_hlist_start_rcu — start an iteration of a hlist protected by RCU 🦋

🌸 SYNOPSIS 🌸

struct hlist_node * seq_hlist_start_rcu (struct hlist_head *head ,
loff_t pos );

like... that's the whole signature, and it's giving "small but crucial" energy ngl ✨

🎀 ARGUMENTS 🎀

  • head — the head of the hlist. yep, the actual list head, this is where the traversal begins 💅
  • pos — the start position of the sequence. this is where you wanna begin, bestie 📍

💜 DESCRIPTION 💜

so this one gets called at seq_file->op->start. that's the hook, that's the vibe check ✅

the important thing, and i mean the important thing: this list-traversal primitive may safely run concurrently with the _rcu list-mutation primitives — things like hlist_add_head_rcu — as long as the traversal is guarded by rcu_read_lock. 🔒

no cap, that guard is not optional. traversal + mutation without rcu_read_lock guarding you is not the move, bestie 😭 keep the lock and everyone's happy 💖

🦋 SEE ALSO 🦋

the whole friend group, all referenced exactly, no gatekeeping 🫶

Kernel file ./fs/seq_file.c and friends:

and that's the page!! 💅 sourced from ./fs, dated October 2026, closing out with seq_hlist_start_rcu(9) one last time because she deserves it 👑 go forth and traverse safely, bestie 🌈✨

📦 where this page comes from