wait_var_event(9)

💖 NAME 💖

okay so welcome to the Kernel API Manual page for wait_var_event(9), bestie ✨ This one is wait_var_event - wait for a variable to be updated and notified. slay.

🦋 SYNOPSIS 🦋

wait_var_event (var , condition );

🎀 ARGUMENTS 🎀

• var — the address of variable being waited on. literally the address, no cap.
• condition — the condition to wait for. yes, that exact vibe.

🌈 DESCRIPTION 🌈

So the whole point: wait for a condition to be true, but only re-checking when a wake up is received for the given var. And var is an arbitrary kernel address — it does not need to be directly related to the given condition, though usually it is. iykyk 💅

The process will wait on a waitqueue selected by hash from a shared pool. It will only be woken on a wake_up for the given address. periodt.

🫶 tiny but huge caveat: the condition should normally use smp_load_acquire or a similarly ordered access, so that any changes to memory made before the condition became true will be visible after the wait completes. no vibes-based memory ordering here, bestie 😭

⭐ SEE ALSO ⭐

Kernel file ./include/linux/wait_bit.h has the whole friend group:

• wait_on_bit(9)
• wait_on_bit_io(9)
• wait_on_bit_timeout(9)
• wait_on_bit_action(9)
• wait_on_bit_lock(9)
• wait_on_bit_lock_io(9)
• wait_on_bit_lock_action(9)
• wait_var_event_io(9)
• wait_var_event_killable(9)
• wait_var_event_timeout(9)
• wait_var_event_interruptible(9)
• wait_var_event_any_lock(9)
• wait_var_event_spinlock(9)
• wait_var_event_mutex(9)
• wake_up_var_protected(9)
• wake_up_var_locked(9)
• clear_and_wake_up_bit(9)
• test_and_clear_wake_up_bit(9)
• atomic_dec_and_wake_up(9)
• store_release_wake_up(9)

kisses bestie 💋 this page’s source/version info is ./include/linux, dated October 2026, and it’s the wait_var_event(9) manual page. mwah 💜