sync_test_and_set_bit(9)

🌸 NAME 🌸

okay so bestie, we’re on the sync_test_and_set_bit(9) page of the Kernel API Manual, and the whole point is literally: set a bit and return its old value. That’s the serve. That’s the moment. 💅

✨ SYNOPSIS ✨

bool sync_test_and_set_bit (long nr , volatile unsigned long *addr );

🎀 ARGUMENTS 🎀

• nr — the bit to set. Like, which little bit is getting the glow-up.
• addr — the address to count from.

🔥 DESCRIPTION 🔥

No cap: this operation is atomic and cannot be reordered. It also implies a memory barrier. That’s the whole flex, fr fr — do not sleep on it. 🫶

🦋 SEE ALSO 🦋

The kernel file ./arch/x86/include/asm/sync_bitops.h is right there, and these other icon pages are in the group chat:

• sync_set_bit(9)
• sync_clear_bit(9)
• sync_change_bit(9)
• sync_test_and_clear_bit(9)
• sync_test_and_change_bit(9)

Bye bestie! Signing off from the ./arch/x86/include/asm source/version corner, dated October 2026 — mwah 💋✨