raw_atomic64..._sub_acquire(9)

📦 version 7.3.1, in nixpkgs unstable

💅 raw_atomic64..._sub_acquire(9) — Kernel API Manual

okay so bestie, welcome to the Kernel API Manual, section 9 (that's the kernel-API shelf, iykyk) 💖 today's main character is raw_atomic64_fetch_sub_acquire, and yeah the header does that whole raw_atomic64..._sub_acquire(9) abbreviating thing — truncated but iconic, we love a mysterious queen. hydrate and let's go ✨

🌸 NAME 🌸

raw_atomic64_fetch_sub_acquire — atomic subtract with acquire ordering 🎀 that's it, that's the whole vibe.

✨ SYNOPSIS ✨

s64 raw_atomic64_fetch_sub_acquire (s64 i , atomic64_t *v );

literally just two little arguments and a s64 coming back out. no drama. 🫶

🦋 ARGUMENTS 🦋

  • i — an s64, and it's the value to subtract. the amount getting yeeted. 💅
  • v — pointer to atomic64_t. the actual thing being updated. the one holding the number.

🎀 DESCRIPTION 🎀

So what happens is: it atomically updates v to (v - i) with acquire ordering. atomically means nobody can catch it mid-subtraction — it's a whole thing or nothing, no in-between, no crumbs 💀 and the acquire ordering part is right there in the name so you already knew.

💖 real talk bestie: Safe to use in noinstr code — but prefer atomic64_fetch_sub_acquire elsewhere. that's the assignment. raw_ is the noinstru-ment, everything else gets the regular one. no cap.

🔥 RETURN 🔥

The original value of v — like, the value from before the subtraction, bestie. that's the whole point of the fetch_ prefix, it hands you the old number while it updates the thing. 😭

🌈 SEE ALSO 🌈

the lore lives in the kernel file <./include/linux/atomic/atomic-arch-fallback.h> 👑 and here's the entire friend group — everyone invited, nobody left out, fr fr:

okay that's the whole page, you ate that 🍓 source of this little masterpiece is <./include/linux/atomic>, dated October 2026, and it's filed under raw_atomic64..._sub_acquire(9) — go forth and subtract atomically, bestie 💜✨

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