atomic_long_cmpxchg(9)

📦 version 7.3.1, in nixpkgs unstable

✨ atomic_long_cmpxchg(9) ✨

okay so real quick — this page is straight out of the Kernel API Manual, section 9, and the star of the show is atomic_long_cmpxchg. bestie, it's a compare-and-swap and it's lowkey iconic 💅

🎀 NAME 🎀

atomic_long_cmpxchg — atomic compare and exchange with full ordering

like, it compares, it exchanges, and it does the ordering thing fully. no cap ✨

🦋 SYNOPSIS 🦋

long atomic_long_cmpxchg (atomic_long_t *v , long old , long new );

🌸 ARGUMENTS 🌸

  • v — pointer to atomic_long_t. it's giving "the thing we're messing with" 🫶
  • old — the long value to compare with. the vibe check value, basically 🌈
  • new — the long value to assign. what we swap in if the vibe check passes 💖

💜 DESCRIPTION 💜

okay so picture this: if (v == old), it atomically updates v to new, and it does that with full ordering. slay.

otherwise, v is not modified and relaxed ordering is provided. so like, nothing happens to your value, and the ordering gets downgraded. not me being chill about it 🙈

⚠️ Unsafe to use in noinstr code — use raw_atomic_long_cmpxchg there instead. fr fr, don't do it, that's the whole warning 💀

⭐ RETURN ⭐

the original value of v. that's it, that's the return. it's giving receipts 👑

👑 SEE ALSO 👑

first up, the kernel file this all lives in: ./include/linux/atomic/atomic-instrumented.h 🧚

💫 the atomic_* crew

🦋 the atomic64_* crew

💖 the atomic_long_* crew (our homegirls)

and that's the whole page, bestie 🫶 this cutie lives in ./include/linux/atomic, dated October 2026 — go read it, periodt 💅✨

📦 where this page comes from