atomic64_cmpxchg_relaxed(9)

📦 version 7.3.1, in nixpkgs unstable

atomic64_cmpxchg_relaxed(9) is your girl, and this is the Kernel API Manual entry for her. Bestie, gather round — this one is lowkey iconic 💅

🌸 NAME 🌸

atomic64_cmpxchg_relaxed — it's an atomic compare and exchange with relaxed ordering. No cap, that's the whole name vibe ✨

✨ SYNOPSIS ✨

s64 atomic64_cmpxchg_relaxed (atomic64_t *v , s64 old , s64 new );

💅 ARGUMENTS 💅

  • v — pointer to atomic64_t. Like, a pointer to the atomic 64-bit thing you're doing the lil compare-and-exchange on 🫶
  • old — s64 value to compare with
  • new — s64 value to assign

🦋 DESCRIPTION 🦋

Okay so picture this: if (v == old), it atomically updates v to new with relaxed ordering. If that compare does not hit, then v is not modified and relaxed ordering is provided. That's the tea ☕

⚠️ Unsafe to use in noinstr code — use raw_atomic64_cmpxchg_relaxed there instead. No exceptions, bestie. This is important for real 💀

🍓 RETURN 🍓

It returns the original value of v. That's it. That's the return. 💖

👑 SEE ALSO 👑

Kernel file: ./include/linux/atomic/atomic-instrumented.h — and the whole extended friend group is here:

Cute lil sign-off bestie: source/version is ./include/linux/atomic, date is October 2026, and yep, the manual is atomic64_cmpxchg_relaxed(9). Periodt 💜🎀

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