futex_unlock_pi(9)

📦 version 7.3.1, in nixpkgs unstable

💅 futex_unlock_pi(9) — Kernel API Manual, section 9

okay so bestie, we're in the Kernel API Manual (section 9, kernel-space girlies only ✨) and today's main character is futex_unlock_pi.

✨ NAME ✨

futex_unlock_pi — release uaddr as a PI mutex, waking the top waiter 🎀

That's the whole job description and honestly? She ate. You hand her a uaddr, she drops it as a PI mutex, and the top waiter gets the wake-up. Periodt. 🌸

🎀 SYNOPSIS 🎀

int futex_unlock_pi (futex_t *uaddr , int opflags );

That's the exact signature, bestie — int coming back at you, futex_t *uaddr and int opflags going in. Don't @ me about the spacing, that's literally how it's written. 💅

🫶 ARGUMENTS 🫶

  • uaddr — the manpage says -- undescribed -- and like… yeah. 😭 That's the whole entry. No cap, the source doc just did not describe it. I'm not gonna invent lore for you, so: it's a futex_t *, it's the uaddr, and per the NAME section it's the thing you're releasing as a PI mutex. That's everything the page actually gives us!
  • opflags — also -- undescribed --. 🙈 An int, sitting there, un-described, iconic in a mysterious way. The docs don't say what goes in it, so I'm not gonna make something up. If you need the real tea, go bother the source (see SEE ALSO below, she's right there 👀).
listen — two whole -- undescribed -- entries is not me being lazy, that's genuinely what the page contains. I refuse to fabricate flag behavior for the group chat. 🫶

🌈 SEE ALSO 🌈

The kernel file to go touch grass in:

  • ./tools/testing/selftests/futex/include/futextest.h

And the whole futex friend group, in the exact order the page lists them 💖:

notice how futex_lock_pi(9) is literally right there — she's the unlock's other half, the lock to your unlock, the main character to your love interest 🦋

🌟 the cute sign-off 🌟

This page is from ./tools/testing/selftests/fute... (the source line got truncated by the terminal, not by me, blame the formatting bestie 😭) and it's dated October 2026, and it signs off as futex_unlock_pi(9).

so yeah — that's the whole page. go unlock that PI mutex, wake that top waiter, and slay 👑💜

📦 where this page comes from