arch_test_and_change_bit(9)

💖 NAME 💖

Okay so this is arch_test_and_change_bit(9) from the Kernel API Manual, and her whole thing is: change a bit and return its old value. Bestie, it’s giving tiny atomic main-character energy. ✨

🌸 SYNOPSIS 🌸

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

🎀 ARGUMENTS 🎀

• nr — the bit to change. That’s the one, bestie. 💅
• addr — the address to count from. That’s the exact wording, don’t come for me 🫶.

✨ DESCRIPTION ✨

No cap: this operation is atomic and cannot be reordered. It also implies a memory barrier. Periodt. Those are the facts, and they’re the whole point — don’t skip them just because the section is short. 💀🔥

🦋 SEE ALSO 🦋

Kernel file ./arch/riscv/include/asm/bitops.h is where it lives. The whole friend group:

• __ffs(9)
• __fls(9)
• ffs(9)
• fls(9)
• arch_test_and_set_bit(9)
• arch_test_and_clear_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)

Source/version tea: ./arch/riscv/include/asm · date on the page: October 2026 — that’s the footer, bestie. Bye! 💖🎀