set_bit(9)

✨ set_bit(9) ✨

okay bestie, welcome to the Kernel API Manual 💖 this is the page for set_bit, and it's honestly iconic — a tiny little function that flips bits in memory atomically and does not make a whole thing out of it. no cap. 🎀

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🌸 NAME 🌸

set_bit — atomically set a bit in memory 💅 like, one single bit. one. and it locks it down so nobody else can snatch it mid-flip. periodt.

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🦋 SYNOPSIS 🦋

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

that's the whole vibe. void return, so don't come looking for a status code, there isn't one, she returns nothing and she's at peace with that 🫶

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🎀 ARGUMENTS 🎀

• nr — the bit to set. which bit, bestie. which one. this is the one. ✨
• addr — the address to start counting from. the starting point, the home base, the place from which we begin counting bits like the little main characters we are 💜

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💅 DESCRIPTION 💅

so here's the tea: this is a relaxed atomic operation — meaning no implied memory barriers 😭 yes, you heard me. it's atomic, it sets the bit safely against concurrent modifications, but it does not sneak in any memory barriers for you. if you need ordering guarantees, that's a you problem, go look at the barrier functions, this one's just here to flip a bit and leave 🦋

and the second thing, which is lowkey the coolest part: nr may be almost arbitrarily large 💀 like, go off. this function is not restricted to acting on a single-word quantity — it'll happily wander across multiple words in memory to reach the bit you asked for. she's flexible. she's got range. she ate. 👑

💀 real talk though: "relaxed" and "no implied memory barriers" are load-bearing words here — don't go assuming ordering that this function never promised. read the caveat, bestie, i'm begging 🙈

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⭐ SEE ALSO ⭐

• Kernel file ./include/asm-generic/bitops/instrumented-atomic.h — like, the actual source, iykyk 🧚
• clear_bit(9)
• change_bit(9)
• test_and_set_bit(9)
• test_and_clear_bit(9)
• test_and_change_bit(9)

the whole bit-flipping friend group 💖 go say hi to all of them, they're all slaying in their own little atomic way 🌈

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🍓 sign-off 🍓

this absolute gem comes to you straight from the kernel file ./include/asm-generic/bitops, dated October 2026, and it's filed under set_bit(9) — remember the name, she's a legend 👑💜 bye bestie, go set some bits responsibly!! 🎀✨