xchg_tail(9)

💖 NAME 💖

okay so bestie, welcome to xchg_tail(9) from the Kernel API Manual — it’s literally the page for putting in the new queue tail code word & retrieving the previous one 💅✨

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✨ SYNOPSIS ✨

u32 xchg_tail (arena_spinlock_t __arena *lock , u32 tail );

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🎀 ARGUMENTS 🎀

• lock — pointer to the queued spinlock structure, bestie 🫶
• tail — the new queue tail code word, no cap 🦋

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🦋 RETURN 🦋

you get back the previous queue tail code word — iconic, honestly 👑

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🌸 DESCRIPTION 🌸

the manpage keeps it super simple and says:

xchg(lock, tail)

and then, fr fr:

p,*,* -> n,*,* ; prev = xchg(lock, node)

that’s the whole vibe check 😌💜

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🔥 SEE ALSO 🔥

Kernel file: ./tools/testing/selftests/bpf/libarena/include/bpf_arena_spin_lock.h

also go peek at these besties:

• clear_pending(9)
• clear_pending_set_locked(9)
• set_locked(9)
• arena_spin_trylock(9)
• arena_spin_lock(9)
• arena_spin_unlock(9)

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mwah 💋 stay slay — source/version is ./tools/testing/selftests/bpf/..., dated October 2026, and that’s the xchg_tail(9) moment 🧚🎀