atomic64_try...xchg_relaxed(9)

📦 version 7.3.1, in nixpkgs unstable

💅 atomic64_try...xchg_relaxed(9) — from the Kernel API Manual, bestie ✨

okay so this one is from the Kernel API Manual, and it's called atomic64_try_cmpxchg_relaxed — yes the header is abbreviated, that's just how the page name got truncated, don't panic 🫶. It's literally a 64-bit atomic compare-and-exchange, but the ordering is relaxed (we'll get to that), and it comes with a try vibe so it tells you if it worked instead of just silently doing stuff. let's go 🦋

🌸 NAME 🌸

atomic64_try_cmpxchg_relaxed — atomic compare and exchange with relaxed ordering. periodt. 💅

⭐ SYNOPSIS ⭐

bool atomic64_try_cmpxchg_relaxed (atomic64_t *v , s64 *old , s64 new );

it returns a bool, icon behavior, we love to see it 👑

🎀 ARGUMENTS 🎀

  • v — pointer to atomic64_t — the main character, the thing getting compared and exchanged. 🧚
  • old — pointer to a s64 value to compare with. yes it's a pointer, so it can get written back to, keep reading 👀
  • new — a s64 value to assign. the new era.

🦋 DESCRIPTION 🦋

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

Otherwise — and this is the part you gotta pay attention to, bestie 😭 — v is not modified, old is updated to the current value of v, and relaxed ordering is provided. so old does double duty: it's the thing you compare against and the place the current value gets dropped back into when the compare fails. iykyk ✨

💀 Caveat, and it's a real one: unsafe to use in noinstr code. use raw_atomic64_try_cmpxchg_relaxed there instead. no cap, don't mix those up.

🔥 RETURN 🔥

  • true — the exchange occurred 🎉 (you ate)
  • false — it did not 🌧️

👑 SEE ALSO 👑

the source for all this is the kernel file ./include/linux/atomic/atomic-instrumented.h, and honestly there are SO many siblings, look at this family tree 🌈:

like i said. HUGE family. every single one is in the group chat 💖

that's the whole thing bestie, go be atomic out there 🫶✨

🌸 this page came from ./include/linux/atomic and it's dated October 2026 — so yeah, it's from the future, main character energy only. mwah 💋 — atomic64_try...xchg_relaxed(9), signing off 🎀
📦 where this page comes from