wait_on_bit(9)

💖 wait_on_bit(9) 💖

okay so bestie, welcome to the Kernel API Manual page for wait_on_bit(9) — it's giving “sleep until that bit is cleared” energy and honestly? iconic. 🦋

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✨ NAME ✨

wait_on_bit — wait for a bit to be cleared 💅

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✨ SYNOPSIS ✨

the signature is literally right here, no cap:

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

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✨ ARGUMENTS ✨

• word — the address containing the bit being waited on 🎀
• bit — the bit at that address being waited on ✨
• mode — the task state to sleep in 😴

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✨ DESCRIPTION ✨

okay so this function waits for the given bit in an unsigned long or bitmap (see DECLARE_BITMAP) to be cleared. yes, that bit. the one you're obsessed with. 🫶

the clearing of the bit must be signalled with wake_up_bit, often as clear_and_wake_up_bit. like, do not forget this part, bestie — it's the whole vibe. 💀

the process will wait on a waitqueue selected by hash from a shared pool. and here's the cute part: it will only be woken on a wake_up for the target bit, even if other processes on the same queue are waiting for other bits. main character energy only. 👑

the returned value will be zero if the bit was cleared — in which case the call has ACQUIRE semantics — or -EINTR if the process received a signal and the mode permitted wake up on that signal. periodt. 💖

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✨ SEE ALSO ✨

the kernel file is ./include/linux/wait_bit.h, and the bestie list is:

• 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(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)

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signed, sealed, slayed from ./include/linux — October 2026 — for wait_on_bit(9) 💌✨