atomic64_add_return(9)

📦 version 7.3.1, in nixpkgs unstable

👑 atomic64_add_return 👑

okay so real talk, bestie — this is the atomic64_add_return page from the Kernel API Manual, and it's honestly kind of iconic for how much it does with so little. Like, the whole thing is four sentences and then a SEE ALSO section that goes on forever (me at a party fr fr 💀).

💖 NAME 💖

atomic64_add_return — atomic add with full ordering. that's it, that's the vibe ✨

🎀 SYNOPSIS 🎀

s64 atomic64_add_return (s64 i , atomic64_t *v );

like, copy it exactly, don't @ me about the spacing 🫶

🦋 ARGUMENTS 🦋

  • i — the s64 value you're adding. the amount. the little extra you're sliding in 💅
  • v — pointer to an atomic64_t. this is your target, your main character, the one getting updated 🌸

🔥 DESCRIPTION 🔥

so what it actually does: it atomically updates v to (v + i) with full ordering. atomically means nobody's gonna catch it mid-update, no weird partial states, no race-condition drama, we do not do that here 🔒✨ full ordering means the memory ordering is the whole package, not the relaxed little cousin version.

⚠️ okay but listen — this is unsafe to use in noinstr code. not "kind of sketchy," actually unsafe. if you're in noinstr territory, use raw_atomic64_add_return there instead. periodt 💀

⭐ RETURN ⭐

it hands you back the updated value of v. so like, the value after the add, not before. that's the difference between this and the fetch-flavoured ones, iykyk 🌈

🌈 SEE ALSO 🌈

so. this is the part where it goes off. the kernel file is ./include/linux/atomic/atomic-instrumented.h and the whole family reunion is listed below — every single one of them, no cap 👑

the atomic_ girlies 💅

the atomic64_ squad 🦋 (our girl's home team)

and the atomic_long_ cousins 🌸

okay and before I go — the source for all this is ./include/linux/atomic, dated October 2026, and the page itself is atomic64_add_return(9). mwah, go add some numbers atomically bestie 🧚‍♀️💜

📦 where this page comes from