atomic_sub_return(9)

📦 version 7.3.1, in nixpkgs unstable

💅 atomic_sub_return(9) — Kernel API Manual, but make it make sense

okay so bestie, welcome to atomic_sub_return(9), your new fave little kernel function from the Kernel API Manual. she's small, she's atomic, she has full ordering, and she's about to subtract a number from your atomic_t like it's nothing. slay.

✨ NAME ✨

atomic_sub_return — atomic subtract with full ordering. that's it, that's the whole vibe. subtracting that also returns, no cap. 🎀

🌸 SYNOPSIS 🌸

int atomic_sub_return (int i , atomic_t *v );

🦋 ARGUMENTS 🦋

  • i — the int value you're subtracting. the amount going bye-bye. 💨
  • v — a pointer to the atomic_t you're messing with. this is the main character.

💜 DESCRIPTION 💜

so here's the tea: she atomically updates v to (v - i) with full ordering. atomically means nobody else can sneak in halfway through and see a cursed in-between state — it all happens as one glamorous unit. ✨ and full ordering means the memory ordering is strict, not vibes-only.

okay so this one matters: it's unsafe to use in noinstr code. if you're living in noinstr land, use raw_atomic_sub_return there instead. fr fr, do not test this. 💀

👑 RETURN 👑

the updated value of v. like, after the subtraction. the new number. the fresh look. 🫶

🌈 SEE ALSO 🌈

the kernel file this lives in is ./include/linux/atomic/atomic-instrumented.h — and honestly the friend group here is huge, so buckle up, we're naming everyone at the party:

and now the 64-bit girlies, atomic64_ edition:

and finally the atomic_long_ crew, the long-distance icons:

okay that's the whole squad 🫶 and before you go — this page came from the kernel file ./include/linux/atomic, dated October 2026, under the atomic_sub_return(9) tag. mwah, bye bestie 💖✨🎀

📦 where this page comes from