srcu_down_read_fast(9)

📦 version 7.3.1, in nixpkgs unstable

✨ srcu_down_read_fast ✨

okay so real talk, this is a page from the Kernel API Manual (yes, that Kernel API Manual 💅) and it's about one very specific little function. buckle up bestie 🎀

🌸 NAME 🌸

srcu_down_read_fast — register a new reader for an SRCU-protected structure. that's it, that's the whole job, and it does it fast 🦋

🫶 SYNOPSIS 🫶

struct srcu_ctr __percpu * srcu_down_read_fast (struct srcu_struct *ssp );

like yes, the return type has a space in it before the *, no we are not going to fix it, it's iconic and we respect it 😌

💖 ARGUMENTS 💖

  • ssp — the srcu_struct where you're registering your brand new reader. that's the whole vibe check. that's the parameter. 🍓

🔥 DESCRIPTION 🔥

okay so here's the tea: calling this drops you into a semaphore-like SRCU read-side critical section — but specifically for a lightweight smp_mb-free reader. no memory barrier, no heavy lifting, just vibes and correctness ✨

if you want the full lore, go read srcu_read_lock_fast and srcu_down_read, because this page is just the cool younger sibling pointing you at them. iykyk 📚

and here's the part where you actually have to pay attention, bestie — the same srcu_struct can totally be used concurrently by both srcu_down_read_fast and srcu_read_lock_fast. no cap, that's allowed. 🎉

BUT 💀 the exact same definition/initialization requirements that are called out for srcu_read_lock_fast_updown still apply here. do not skip those. do not skim those. do not "yeah yeah i know" those. they apply. periodt. 👑

🌈 SEE ALSO 🌈

go be nosy, there's a whole friend group here 🫶

kernel file ./include/linux/srcu.h plus all of these absolute legends:

and that's the whole page! mwah 💋 this one lives in ./include/linux, stamped October 2026, straight out of the Kernel API Manual — stay hydrated, read your barriers, and go register a reader for me 🧚💜

📦 where this page comes from