wait_var_event_any_lock(9)

📦 version 7.3.1, in nixpkgs unstable

✨ wait_var_event_any_lock(9) ✨

okay so this is wait_var_event_any_lock from the Kernel API Manual and bestie, it's literally the "wait for a variable to update while you're holding a lock" girlie 💅 buckle up.

🌸 NAME 🌸

wait_var_event_any_lock — wait for a variable to be updated under a lock 🔒

🦋 SYNOPSIS 🦋

wait_var_event_any_lock (var , condition , lock , type , state );

like that's the whole vibe, five args, no cap 🫶

🎀 ARGUMENTS 🎀

  • var — the address of the variable being waited on 📍 like, the actual thing you're staring at until it changes
  • condition — condition to wait for, the "am I done yet" check ⏳
  • lock — the object that is locked to protect updates to the variable 🔐 it's giving bodyguard energy
  • type — prefix on lock and unlock operations ✨ yep, just a prefix, it's a whole build-your-own-function-name situation
  • state — waiting state, TASK_UNINTERRUPTIBLE etc. 😴 the mood you're in while waiting

💖 DESCRIPTION 💖

So the whole concept: you wait for a condition that can only be reliably tested while holding a lock. fr fr, you can't just peek at it whenever.

The variables assessed in the condition will normal be updated under the same lock, and the wake up should be signalled with wake_up_var_locked under the same lock. 🔔 (yes it says "normal" in the original, we're not fixing it, we're respecting it 🙈)

This is similar to wait_var_event, but assumes a lock is held while calling this function and while updating the variable. close cousins, different priorities 💫

Lowkey important: this must be called while the given lock is held 🤏 and the lock will be dropped when schedule is called to wait for a wake up, and will be reclaimed before testing the condition again. So it's locking, unlocking, napping, waking up, re-locking, re-checking. main character multitasking energy 👑

The functions used to unlock and lock the object are constructed by appending _unlock and _lock to type. 🛠️ so if type is foo you get foo_unlock and foo_lock — it's literally string arts and crafts, iconic.

Return -ERESTARTSYS if a signal arrives which is allowed to interrupt the wait according to state. 😭 so if a signal shows up and state says it's allowed to interrupt you, you get -ERESTARTSYS back, periodt.

🌈 SEE ALSO 🌈

Kernel file ./include/linux/wait_bit.h — and the whole friend group 💜:

🧚 sign-off besties: this one lives in ./include/linux, dated October 2026, and it's filed under wait_var_event_any_lock(9). slay, go lock something responsibly 💅✨🎀
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