__clear_bit_unlock(9)

💖 NAME 💖

__clear_bit_unlock — clears a bit in memory. Okay bestie, this is the __clear_bit_unlock(9) page from the Kernel API Manual, and it is lowkey giving “tiny function, serious barrier business” energy ✨

📜 SYNOPSIS 📜

void __clear_bit_unlock (long nr , volatile unsigned long *addr );

🧠 ARGUMENTS 🧠

• nr — the bit to clear. Yep, that’s the one getting cleared, no cap.
• addr — the address to start counting from. That’s the starting point for the whole bit-finding mission, bestie 💅

✨ DESCRIPTION ✨

So the vibe here is: this is a non-atomic operation, but it implies a release barrier before the memory operation. Like, it’s not out here doing the full atomic dance, but it is setting that release-barrier energy before the memory operation. Slay.

It can be used for an unlock if no other CPUs can concurrently modify other bits in the word. That “if” is doing a LOT of heavy lifting, so please respect it — no other CPUs touching other bits in the same word at the same time, periodt. 🫶

🔗 SEE ALSO 🔗

• Kernel file ./include/asm-generic/bitops/instrumented-lock.h
• clear_bit_unlock(9)
• test_and_set_bit_lock(9)
• xor_unlock_is_negative_byte(9)

xoxo from the ./include/asm-generic/bitops girlies, October 2026, with __clear_bit_unlock(9) signing off 💋💖