__rt_mutex_start_proxy_lock(9)

📦 version 7.3.1, in nixpkgs unstable

💅 __rt_mutex_start_proxy_lock(9) — like, the Kernel API Manual page you actually want to read

okay so bestie, we're in the Kernel API Manual today and the star of the show is __rt_mutex_start_proxy_lock. Yes it has a lot of underscores. No we're not scared of it. Let's go 🎀

✨ NAME ✨

__rt_mutex_start_proxy_lock — Start lock acquisition for another task

Like, you're not grabbing the lock for yourself, you're doing it on behalf of somebody else. Very main character of you, honestly 🫶

🌸 SYNOPSIS 🌸

int __rt_mutex_start_proxy_lock (struct rt_mutex_base *lock , struct
rt_mutex_waiter *waiter , struct task_struct *task , struct wake_q_head
*wake_q );

So it returns an int, and it takes four things. Four! We love a four-argument era 💅

🦋 ARGUMENTS 🦋

  • lock — the rt_mutex to take. That's the whole point, that's the vibe 💖
  • waiter — the pre-initialized rt_mutex_waiter. Pre-initialized!! it's already dressed and ready to go, don't redo it ✨
  • task — the task to prepare 👑
  • wake_q — the wake_q to wake tasks after we release the wait_lock. It's giving "we'll deal with y'all in a sec" 🌈

💀 DESCRIPTION 💀

Starts the rt_mutex acquire — so it enqueues the waiter and does the deadlock detection 🕵️‍♀️

Important: it does not wait. If you want the waiting part, that's rt_mutex_wait_proxy_lock, a whole different girlie. Don't @ me 😭

This is a special API call for PI-futex support. iykyk ✨

🙈 NOTE 🙈

This one's serious, so listen up:

It does NOT remove the waiter on failure. Like, at all. Zero cleanup, none, nada. 🚨

So after you call this, you must call either rt_mutex_wait_proxy_lock or rt_mutex_cleanup_proxy_lock. Those are your only two options, bestie. Pick one, fr fr 💀

🍓 RETURN 🍓

  • 0 — task blocked on lock 😴
  • 1 — acquired the lock for the task, and the caller should wake it up ☀️ (yes, that's you)
  • <0 — error 🔥

🧚 SEE ALSO 🧚

First things first, the kernel file: ./kernel/locking/rtmutex_api.c 📁

And then the whole friend group 👯‍♀️:

and that's the whole page, bestie! 💖✨🎀🦋

cute little sign-off: this one lives under ./kernel/locking and it's dated October 2026 📅 — go forth and proxy-lock responsibly, ok? love u, bye 👑💜

📦 where this page comes from