arena_spin_lock(9)

💅 arena_spin_lock(9) — Kernel API Manual, bestie ✨

Okay so welcome to the arena_spin_lock(9) page from the Kernel API Manual. It’s giving “tiny function, very specific rules,” and we’re gonna get into it 🫶

---

🌸 NAME 🌸

arena_spin_lock — acquire a queued spinlock. Periodt. 💅

✨ SYNOPSIS ✨

int arena_spin_lock (arena_spinlock_t __arena *lock );

🎀 ARGUMENTS 🎀

• lock — pointer to the queued spinlock structure. That’s the whole argument, bestie, keep it moving 🦋

💖 DESCRIPTION 💖

On error, the returned value will be negative. On success, zero is returned. Simple as that.

🚨 okay, this part is highkey important: the return value _must_ be tested against zero for success, instead of checking it against negative, for passing the BPF verifier. Do not be out here doing < 0 checks like it’s a normal day — the BPF verifier said no 💀

The user should do:

• if (arena_spin_lock(...) != 0) // failure
• or if (arena_spin_lock(...) == 0) // success
• or if (arena_spin_lock(...)) // failure
• or if (!arena_spin_lock(...)) // success

instead of:

• if (arena_spin_lock(...) < 0) // failure

And yes, the return value can still be inspected later 👀✨

🦋 SEE ALSO 🦋

• Kernel file: ./tools/testing/selftests/bpf/libarena/include/bpf_arena_spin_lock.h
• xchg_tail(9)
• clear_pending(9)
• clear_pending_set_locked(9)
• set_locked(9)
• arena_spin_trylock(9)
• arena_spin_unlock(9)

---

okay bye bestie, this little page is from source/version ./tools/testing/selftests/bpf/... and dated October 2026 — arena_spin_lock(9) out 💖✨