wait_var_event_spinlock(9)

📦 version 7.3.1, in nixpkgs unstable

💅 wait_var_event_spinlock — kernel API manual, but make it make sense

okay so bestie, welcome to wait_var_event_spinlock(9) from the Kernel API Manual. this one's a spinlock girlie and she's literally so specific about it 🎀

✨ NAME ✨

wait_var_event_spinlock — wait for a variable to be updated while you're holding a spinlock. that's it, that's the whole vibe 💅

🦋 SYNOPSIS 🦋

wait_var_event_spinlock (var , condition , lock );

no cap, three things go in and then you just... wait ✨

🌸 ARGUMENTS 🌸

  • var — the address of the variable you're waiting on. yes, the address, not the value, she needs to know where to look 👀
  • condition — the condition you're waiting for. the thing that has to become true before you can go home 🫶
  • lock — the spinlock that protects updates to the variable. she's the bodyguard fr fr 🔥

💖 DESCRIPTION 💖

so here's the tea: you use this when you've got a condition that can only be reliably tested while you're holding a spinlock. like, the vibe check literally cannot happen without the lock held 🙈

the variables being assessed in the condition will normally be updated under that same spinlock, and the wake up should be signalled with wake_up_var_locked — also under the same spinlock. matching set, iykyk 💅

this is similar to wait_var_event, but it assumes a spinlock is held while you're calling this function and while the variable is being updated. very "we do everything together" energy ✨

and here's the important bit: this must be called while the given lock is held. the lock gets dropped when schedule is called to wait for a wake up, and it'll be reclaimed before the condition is tested again. so she leaves for a sec, comes back, re-checks, iconic behaviour honestly 👑

🌈 SEE ALSO 🌈

it's giving "linked list of friends" and honestly? obsessed. all of these live in the kernel file ./include/linux/wait_bit.h:

twenty whole besties, and honestly every single one of them ate 💀🫶

💀 real talk reminder: the lock is held when you call this, and it gets dropped during schedule. don't be weird about it, that's literally the whole design 😭

and that's the page!! sourced from ./include/linux, dated October 2026, and living in the Kernel API Manual. go forth and wait on your variables, bestie — you're gonna slay 🌸✨🎀💜

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