init_srcu_st..._fast_updown(9)

📦 version 7.3.1, in nixpkgs unstable

💅 init_srcu_st..._fast_updown(9) — the Kernel API Manual, bestie edition 🎀

okay so we're in the <pink>Kernel API Manual</pink> today and this page is literally called init_srcu_st..._fast_updown(9) (yes the name is truncated with dots, that's just how it is, no cap). Buckle up 🦋

✨ NAME ✨

init_srcu_struct_fast_updown — this one initializes a fast-reader up/down sleep-RCU structure. it's giving setup era, it's giving "before anything else happens, do this" 👑

🌸 SYNOPSIS 🌸

int init_srcu_struct_fast_updown (struct srcu_struct *ssp );

like, that's the whole signature. one argument. one int coming back at you. slay 💅

🫶 ARGUMENTS 🫶

  • ssp — the structure to initialize. that's it, that's the whole vibe. it's the thing you're setting up 💖

🔥 DESCRIPTION 🔥

okay so here's the tea ☕: use this function in place of DEFINE_SRCU_FAST_UPDOWN and DEFINE_STATIC_SRCU_FAST_UPDOWN for non-static srcu_struct structures — the ones that are gonna get passed to srcu_read_lock_fast_updown, srcu_down_read_fast, and friends.

and here's the part you cannot skip, bestie: it is necessary to invoke this on a given srcu_struct before passing that srcu_struct to any other function. like, any other function. no exceptions. don't be out here passing an uninitialized struct around, that's not the move 😭

each srcu_struct represents a separate domain of SRCU protection — so like, one struct = one domain, they're all doing their own thing, main character energy each 👑

🦋 SEE ALSO 🦋

Kernel file ./kernel/rcu/srcutree.c, plus the whole friend group:

iykyk 💜

ngl if you take one thing from this page: init first, pass second. that's the whole plot 🙈

⭐ and that's the page!! this iconic little number lives in ./kernel/rcu, it's dated October 2026, and it answers to the name init_srcu_st..._fast_updown(9). periodt 💅✨🍓

📦 where this page comes from