wait_on_bit_lock_io(9)

💅 wait_on_bit_lock_io — from the Kernel API Manual, bestie 💖

okay so picture this: you're a kernel dev, you need a bit, but the bit isn't ready yet. that's literally this function's whole job. welcome 🫶

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✨ NAME ✨

wait_on_bit_lock_io — wait for a bit to be cleared, then set it. that's it. that's the vibe. 👑

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🎀 SYNOPSIS 🎀

int wait_on_bit_lock_io (unsigned long *word , int bit , unsigned mode
);

yes the formatting is a little chaotic, no we're not fixing it, it's iconic 💅

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🌸 ARGUMENTS 🌸

• word — the address containing the bit we're waiting on. like, the actual location. point at it.
• bit — which bit of the word we're waiting on and setting. very specific queen behavior ✨
• mode — the task state to sleep in. this is your napping settings, basically 😴

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🦋 DESCRIPTION 🦋

so here's the tea ☕: you wait for the given bit in an unsigned long or bitmap (peep DECLARE_BITMAP) to be cleared. someone else has to signal that clearing with wake_up_bit — often as clear_and_wake_up_bit — otherwise you're just sitting there, and not in a cute way 😭

the moment it's clear, this function atomically sets it and returns. no gaps, no drama, atomic and slay 🔥

it's super similar to wait_on_bit_lock, but it calls io_schedule instead of schedule. that one swap is the entire plot twist, iykyk 💀

now for the return values, bestie, pay attention:

• returns zero if the bit was (eventually) found to be clear and was set ✅
• returns non-zero if a signal was delivered to the process and the mode allows that signal to wake the process 📬

fr fr: if you set your mode so signals can wake you, your wait might bail early with non-zero. that's not a bug, that's the feature working exactly as advertised 🧚

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🌈 SEE ALSO 🌈

kernel file ./include/linux/wait_bit.h, plus 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_action(9)
• wait_var_event(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)

go read them all, they're all main characters in their own right 👑

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💖 that's the whole page, no cap. go lock yourself a bit. carefully. atomically. 🎀

mwah 💋 this one came straight outta ./include/linux, dated October 2026, and the page itself is wait_on_bit_lock_io(9) — catch you in the next manpage, bestie 🦋✨