arch_test_and_clear_bit(9)

💖 arch_test_and_clear_bit(9) 💖

okay so bestie, welcome to the Kernel API Manual — the main character is arch_test_and_clear_bit(9), and she is literally here to clear a bit and hand you back its old value. no cap. 🫶

🌸 NAME 🌸

arch_test_and_clear_bit — Clear a bit and return its old value. that's the whole vibe. ✨

✨ SYNOPSIS ✨

int arch_test_and_clear_bit (int nr , volatile unsigned long *addr );

🎀 ARGUMENTS 🎀

• nr — the bit to clear. yes bestie, that one. 💅
• addr — the address to count from. (that's what the page says, i'm not gonna rewrite the lore.) 🎀

💅 DESCRIPTION 💅

this is an atomic, fully-ordered operation with an implied full memory barrier. so like... it does the thing atomically, in full order, and the memory barrier is implied. periodt. 🔥

🦋 SEE ALSO 🦋

the receipts live in the Kernel file ./arch/riscv/include/asm/bitops.h, and the whole squad is:

• __ffs(9)
• __fls(9)
• ffs(9)
• fls(9)
• arch_test_and_set_bit(9)
• arch_test_and_change_bit(9)
• arch_set_bit(9)
• arch_clear_bit(9)
• arch_change_bit(9)
• arch_test_and_set_bit_lock(9)
• arch_clear_bit_unlock(9)
• arch___clear_bit_unlock(9)

kisses bestie 💋 — footer info: source/version ./arch/riscv/include/asm, date October 2026, page arch_test_and_clear_bit(9) 🫶💖