atomic_cmpxchg_relaxed(9)

📦 version 7.3.1, in nixpkgs unstable

💅 atomic_cmpxchg_relaxed — Kernel API Manual, section 9 🎀

okay so bestie, we're in the Kernel API Manual today and the star of the show is atomic_cmpxchg_relaxed(9). it's the chill, low-key sibling of the compare-and-swap family and honestly it ate. let's get into it ✨

🌸 NAME 🌸

atomic_cmpxchg_relaxed — atomic compare and exchange with relaxed ordering

like, you compare, you exchange, and you do not stress about ordering. she's laid back. she's relaxed. she's got main character energy 💅

✨ SYNOPSIS ✨

int atomic_cmpxchg_relaxed (atomic_t *v , int old , int new );

🦋 ARGUMENTS 🦋

  • v — pointer to atomic_t. this is the thing we're messing with 🫶
  • old — int value to compare with. the "is it you, babe?" value 👀
  • new — int value to assign. the "okay you're you, here's your new fit" value 💖

👑 DESCRIPTION 👑

If (v == old), atomically updates v to new with relaxed ordering. Otherwise, v is not modified and relaxed ordering is provided.

so fr fr: match happens → v becomes new, all in one atomic little moment, relaxed ordering the whole way. no match → v stays exactly as it was, and you still get relaxed ordering out of the deal. no cap 💀

⚠️ Unsafe to use in noinstr code; use raw_atomic_cmpxchg_relaxed there. like genuinely, do not do it. noinstr code has rules and this is not the function for that party 🙈

⭐ RETURN ⭐

The original value of v. that's it, that's the tea 🍓 — remember, it's the value from before anything changed, icon behavior 💜

🌈 SEE ALSO 🌈

Kernel file ./include/linux/atomic/atomic-instrumented.h — and okay the whole entire friend group shows up here, so buckle up bestie, we're listing every single one 💖

and that's the whole page bestie!! 🧚 this lil cutie lives in ./include/linux/atomic, dated October 2026, and you can find her filed under atomic_cmpxchg_relaxed(9). go forth and swap atomically, but relaxed, obviously 💖✨🎀

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